: Bent Drive Shaft??



Timothy60
05-18-06, 05:58 PM
If you have been following my posts entitled Seeking Front End Advice, this is a follow-up that I think deserves a new thread.

I took my 93 Fleetwood to a garage today to have the vibration problem checked by a professional since nothing I have been doing has helped even the slightest bit. They kept it all day. This is the verdict:
1. Left rear tire has a flat wear spot; they recommended getting a new tire (which I did today)

2. Bent drive shaft

How would I get a bent drive shaft all of a sudden? I'm the only driver. I did not drive over a curb or anything else that would even remotely endanger anything on the undercarriage. The car was smooth as glass until the last week of April when the vibration started. How can a drive shaft just bend? That's a pretty stout drive shaft, too!

They recommended that I go to a specialist drive shaft place here in Syracuse, NY to have the ends of the shaft cut off and a new tube welded in place. Does that make sense? They said it would cost about $200. I've never heard of a drive shaft bending under normal service conditions. And I've never heard of cutting and welding a drive shaft. Have you? What do you think about this?

Junkman
05-18-06, 10:55 PM
Cutting out the tube and welding in another tube is a common proceedure and if it is done correctly, then it is as good as a new one. I would think that you would be able to find a good driveshaft in a junk yard or $25 or $50. As for how a driveshaft suddenly gets bent, that isn't as much a mystery to me. I have seen it happen when a shop lifts a car on a frame contact lift and the rear axle falls until the shocks stop it. I wonder why they didn't notice this when the driveshaft had the U joints replaced? Without being there and looking at the driveshaft itself, it is hard to tell, but you did say that it happened right after you had the tires changed. Strong possiblility that they messed up doing the job, but now, it will be next to impossible to lay it on them.

Timothy60
05-19-06, 05:14 AM
Junkman, that makes perfect sense. I had those snows removed at BJ's Wholesale. That's exactly the point at which the vibration started. It was that same day; that's why I went back to have them re-balanced. The pieces of the puzzle come together now. . .

Thanks Junkman, I'll let you know how this turns out and how much $$ to fix it.

scurling
05-19-06, 10:35 PM
Timothy:

Check out this site of used parts dealers: http://www.car-part.com/index.htm

I ran a quick search for the NorthEast region and found a wide range of locations with prices from $78.00 to $175.00 for your drive shaft.

Good luck.

davesdeville
05-20-06, 03:58 AM
The first thing I'd do is double check that. Set it on jackstands with bricks on both sides of the front tires, then let it idle in drive, and climb under there. Towards the middle of the driveshaft use a sharpie or something, get it close enough to barely touch the driveshaft. If it's bent or even slightly out of shape you should be able to tell. If it's only very slightly out of balance you can balance it yourself (using hose clamps as balance weights.) Naturally be real careful if you do any of this.

Junkman
05-20-06, 05:51 PM
You can't balance a bent drive shaft, no matter how hard you try. Once bent, it takes on a whole new dynamic when spinning that balance will not cure. Your method, while good in theory, doesn't work very well in practice. Balance is a delicate thing that requires precision in placement. A 1/4 ounce might be all that it takes, and if it is off in either direction, then it will add to the problem of balance. I will liken it to stirring a pot of soup with a shovel..... :stirpot: While it can be done, it can't be done well.... :thepan:

N0DIH
05-21-06, 01:10 AM
Find a good driveshaft shop and have them take a look at it. They can tell you in a flash. I gotta get some time off to have mine done too.

davesdeville
05-21-06, 04:32 AM
You can't balance a bent drive shaft, no matter how hard you try. Once bent, it takes on a whole new dynamic when spinning that balance will not cure. Your method, while good in theory, doesn't work very well in practice. Balance is a delicate thing that requires precision in placement. A 1/4 ounce might be all that it takes, and if it is off in either direction, then it will add to the problem of balance. I will liken it to stirring a pot of soup with a shovel..... :stirpot: While it can be done, it can't be done well.... :thepan:

Now if it's literally bent to the point of causing serious vibration you're right, however an off balance or very slightly bent shaft can be balanced well enough to get rid of most vibration. It's not hard to get the weight aligned in the proper direction. The 2 piece shaft in my Lincoln vibrated quite a bit over 110 or so, since I'm switching from 3.08s to 3.73s or 3.90s that would be unacceptable at normal freeway speeds. Balanced in the method I described above, and the improvement was very noticable. I'll probably switch to the MMX shaft when the budget allows, but that's $500 so this will do for now.

WMD
05-21-06, 09:44 AM
I would let the experts do the balancing act. I think that balancing drive shafts yourself is tedious and never perfect. I would liken it to balancing my own wheels and tires. If it is not bent and if the experts are ABLE to balance it to perfection I would be more than pleased and happy to have the problem over with.
Cheers WMD

The Ape Man
05-21-06, 12:30 PM
Call a few local junkyards for a pre-owned shaft.

Most coil spring cars will find the rear axle supported by the shocks when hoisted on a common garage lift. This is normal and in itself not a problem. What might have happened is that the driveshaft became damaged by positioning the car too far foward when lifting, allowing the shaft to hit the center area of the lift. A good visual check of the driveshaft over 360 degrees would show a dent or scratch if this were the case. I'd get the car in the air (in neutral) and give the driveshaft a good look. If it's got any marks on it then take the car back to where it was worked on and let them know what happened. Let them repair it.

Junkman
05-21-06, 03:32 PM
......... The 2 piece shaft in my Lincoln vibrated quite a bit over 110 or so, since I'm switching from 3.08s to 3.73s or 3.90s that would be unacceptable at normal freeway speeds. ............

I assume that you are referring to 110 MPH!! At that speed, I wouldn't be concerned with a vibration because the vision of angel wings and a halo over my head would be enough preoccupation of thought.... :rolleyes:

davesdeville
05-21-06, 10:29 PM
I was referring to 110mph, I've taken it up that high a few times. Here in the desert southwest between cities it's not uncommon for traffic to move at a 90+ pace. With 3.90s the vibration at 80-90 would become a real issue...

Junkman
05-22-06, 02:28 AM
I was referring to 110mph, I've taken it up that high a few times. Here in the desert southwest between cities it's not uncommon for traffic to move at a 90+ pace. With 3.90s the vibration at 80-90 would become a real issue...

I visited Albuquerque a few years ago and I know what you mean about distances between town. The strange thing is that when I was 25 I drove my Corvair Turbocharged Spyder over 100 MPH and didn't think much of it. Back then, we were driving on rayon cord tires that had a life expectancy of about 15000 miles at best and blow outs were common. Today, the cars are much safer, and the tires are a lot better, but I no longer feel comfortable driving 75 MPH. Must be something about wanting to reach my 100th birthday with all my limbs intact. Just remember, at the speed of 110 MPH, your reaction time, might be 1 second, but the car will have traveled 161.3 feet in that one second. Think about this and be a safe driver. You only get one life to live....

Timothy60
05-22-06, 08:32 AM
I just got back from a Syracuse, NY to Boston, MA round trip with the Fleetwood. I was nervous taking it on such a long trip with that vibration problem, but I had no choice. Anyway, we made it back with no problems.

On the trip I noticed a few things about the vibration issue. After reading all the comments that accumulated on this thread over the weekend, I've come up with a theory that may be WAY OFF but I'm going to suggest it anyway. Here are the two things I noticed:
1. The vibration is reduced during rainstorms.
2, The vibration increases as the driving duration increases.

So. . . here is my theory! It is NOT a bent driveshaft! I don't think a bent or imbalanced driveshaft would be affected by the cooling effect of rain or how long the vehicle is driven. Do you? Would a few drops of water left after the cetrifugal force on a spinning shaft cause it to be suddenly balanced? Would the vibration on a spinning shaft increase as temperature increases?

It is just a theory, but I think a tire has a flaw in it. (I think it's the left front.) I think the mechanic was wrong in diagnosing the bent shaft. I think that as the tire heats up, something happens to it to set up a vibration. When rain cools it, the vibration decreases. When it heats up, it increases. And get this: it was unseasonably cool this morning on my way to work. It was 38 degrees F. Guess what? No vibration until I drove 32 miles and then it was only slight.

So this is what I'm going to do: This evening I'm going to buy 2 brand-new Kelly tires for the front and see what happens before I start anything with the driveshaft. How does that sound? What do you predict?

Junkman
05-22-06, 11:20 AM
I would say that you are on the right track. I suspected a broken belt in the tire originally, but I would also have them check all tires for the defect. When they spin the tire on a balance machine, they might be able to see it, or if the tire is dismounted, then it might show in the inside. I can only make suggestions, and have to work with the information supplied. Junk...

N0DIH
05-22-06, 11:32 AM
I have had broken belts before, they suck. Sometimes you can feel them if they are on the front, they often try to turn the wheel slightly.

Typically a bent shaft can also cause a "body boom" if it binds, say over a bump or something when the suspension is articulating some it will bind and bang. My sisters 65 Mustang had 2 bent shafts and it would shake the 3 speed manual shifter like no tomorrow, 45 mph was rather bad, 65 was scary!!!
New shaft and all was fine. But it took 2 to get a good one.

Timothy60
05-24-06, 01:57 PM
Nope, my theory was wrong. Now I have 4 new Kelly-Springfield Navigator Gold tires and it still vibrates.

N0DIH
05-25-06, 01:46 PM
Bent rim (wheel balance should have caught that), bent axle shaft?, bad rear wheel bearing?

Does it change vibration with load? like if you go over a bump when the car gets lighter momentarily over the bump, does it go away and then increase when the suspension loads back up?

Or in turns, left and right, bears change, tone/vib noises/feel, other things do not.

Timothy60
05-25-06, 02:06 PM
Nope, the rims check out OK. Two mechanics have said the front-end is OK. (One mechanic actually said the front end is in very good shape.) One mechanic thinks it's the driveshaft, the other says it is highly unlikely. Front bearings are good. The vibration doesn't change except if it's cool or damp. Unaffected by engine RPM or braking action. Vibration increases slightly when turning and is present between 35-72 MPH. It goes away completely at 74 MPH. Otherwise the car runs and drives completely normal.

This is my next step: I'm going to remove the driveshaft and bring it to a driveline specialist here in Syracuse. I crawled under the Caddie to check for dents, scratches, or dings in the shaft but I saw nothing. The factory-installed weights are intact. I'll let a professional put it on a balance lathe and check it, but the bad side of that is it will tie up my car and I need it to go to work! Maybe if they work on a Saturday. . .? This driveshaft thing is my last hope. What a bummer to have such a great Cadillac and to have it ride like a piece of junk. A Cadillac is supposed to be smooth!

N0DIH
05-25-06, 02:23 PM
Have you replaced the u-joints?

I have heard GM OEM balanced wasn't worth a whole lot. I need mine does too.

Is there any driveline phasing issues? Like upper/lower rear control arms with bad bushings? That will cause all kinds of issues.

You can put there rear up on jack stands and accelerate car to vibration speeds (disable traction control) and monitor it. Be VERY VERY CAREFUL! Read the FSM on how to do safely. You might catch something. If you have a high speed camera like a digital video, you might be able to see something.

Mine is getting pretty bad at 80+ mph vibrating. I gotta get my driveshaft balanced. Just need a day off work with one car down and one tied up with me driving.

Rick186
05-25-06, 10:43 PM
Following this thread I wonder about the experiences I had with my 1957 Mercury Turnpike Cruiser. It had a SEVERE vibration that started at about 67 mph and went up to about 76 when it cleared up completely!
That was exactly where I wanted to cruise!
Went thru all sorts of wheel balancing, new tires, etc.
Strickland Mercury in Indianapolis traced it to a bent drive shaft and replaced the drive shaft - at my cost, of course, since this was 1960 and I'd bought the car used.
Amazing car. 8mpg in town. 19mpg on the highway if you were VERY careful and didn't exceed 60 with the 368 V-8. Usually I got about 14.

Rick186

Timothy60
06-05-06, 07:11 PM
I finally took an afternoon off to get that "bent" driveshaft repaired. (Paid $75 for that diagnosis two weeks ago.) I made an appointment at a driveline specialist here in Syracuse and left it for the afternoon. The verdict? No bent driveshaft, but it was out of balance which they fixed by welding an iron weight to the rear of the shaft. They installed two new U-joints. Good as new! Sound good so far? How does $181.51 sound? Not bad?

Picked up the car and it still vibrates. No change. What do you suggest I do now?

BluEyes
06-07-06, 09:53 AM
Sounds like the reason why I do as much of my own work as I possibly can! Might leave the balancing to them, but I can do u-joints myself...

okay, so the front-end is good, rims are all good, driveshaft is super-good :) ...

I'd go inspecting wheel bearings at this point.

Have you had the differential pinion shaft and the front yoke on the driveshaft checked for play?

I have heard of wheel hubs being machined slightly off center. The effect is just like an out-of-balance wheel because the center of the wheel and the center of the axle are no longer concentric. You can measure tire runout with the tire mounted on the car to test this

scurling
06-07-06, 12:08 PM
Gee whiz, what a nightmare. Tim, I was hoping your problem was fixed by now. I have purposfully left this thread alone, as most possibilities seems to be covered by everyones comments.

I don't think the problem is with the wheel/tire assembly. The vibration Tim describes is not due to tire or wheel out of balance or out of round. A wheel bearing doesn't usually cause a vibration without other signs of failure. I was really hoping for the axle to be the issue. Aside from that, I would have to revisit the front end linkage components.

If we try, maybe we can make this thread a winner for most entries or longest running. What do you think about that Tim? You know if we keep chipping away at your vehicle, it's going to look brand new before too long.

Timothy60
06-07-06, 12:20 PM
Yes, this has been a nightmare for me. What's really frustrating is that the Fleetwood used to be very s-m-o-o-t-h! Anyway, I have an appointment after work this afternoon to have the wheels checked on a Hunter Road Force balancer at $20 per wheel. (open the wallet again!) If the technician does everything correctly, we should be able to eliminate any more guess work about tire/wheel assembly imbalance issues. I'll let you know how this works out tonight. Thanks for your help and support.

Timothy60
06-08-06, 07:41 AM
Good morning. How about an update? OK, here goes. After work yesterday, I went to the appointment I had to have the wheels checked at the garage who has the Hunter Road Force balancer. What an enlightening experience! The technician sat down with me and asked all sorts of questions about the Cadillac and the vibration problem I'd been having. He said he needs to know the entire history of the problem. Then he said so that I'm not wasting my money, he'd like to take a test drive to see if the Hunter machine would actually be a help in solving this vibration issue. We went out on the highway and back roads, too. He experienced the vibration first-hand so he knew exactly what I was talking about. He said that yes, he thinks the Hunter machine will help, but he can't guarantee it will solve the problem completely, although it may. He said there could be other issues but we'd look into those after determining for sure that the wheel assemblies were OK. I have to go back today after work and they are going to test the wheels. It will be $15-20 per wheel depending on how much adjusting he has to do. He said it will take at least an hour to get it right.
Wow! Finally a mechanic who cares and is willing to take the time to diagnose objectively instead of expensive guesswork! I'm pretty enthusiastic that we're on the right track now. I'll let you know how this works out ASAP.

Oh, and one question for those following this thread. This a shot in the dark. The technician said yesterday that the back end of the Fleetwood seems like it's sitting a little bit high. We're going to check the trim height today, too. So here's the question: If the rear trim height is too high, could that be causing the driveshaft angle to be too sharp thus causing a vibration even if the drivesaft is properly balanced? Or is that a crazy idea?

scurling
06-08-06, 04:29 PM
Tim:

It almost makes it fun to spend your money when someone really helps your cause. :thumbsup:

BCs71
06-08-06, 04:29 PM
So here's the question: If the rear trim height is too high, could that be causing the driveshaft angle to be too sharp thus causing a vibration even if the drivesaft is properly balanced? Or is that a crazy idea?

Well, if the back end of the body is too high, then I don't see that being a aproblem -- at least it won't affect driveshaft or pinion angle since the body is isolated from the rear end assembly. Only way pinion angle would be changed is with taller tires, or severely out-of-whack suspension components.

That said, if the body is too high then it would cause weight distribution issues. Even then I don't see it relating to vibration problems, though.....

Good luck! This is weird! Interested in the solution....

N0DIH
06-08-06, 04:35 PM
Yes, too high will cause the u-joints to be in line with each other and very weird things happen.... They don't like being lined up at all.

"They" claim there is books 2-3 inches thick on how to properly phase a driveline.

Quick fix to see? Disconnect the air line on the compressor, let the car drop lower in ride height, (pull compressor fuse too) and drive. If the problem goes away, you found the problem.

Timothy60
06-08-06, 07:55 PM
(I pulled the 20 amp fuse for the ride leveler just for kicks. Why not?) Anyway. . . here's another update of the situation. I brought the 93 Fleetwood to the appointment I had with the Hunter Road Force balancer, and the owner of the garage wanted to drive the car today. He took it out on Route 690 and around the city. It sure did vibrate perfectly! That's two technicians from the same garage who felt the same effect. His diagnosis? He didn't think the Road Force balancer would really help. They put the Caddie up on a lift and as the three technicians looked at it, they wanted me to look, too. No hanging around in some waiting room! Get right under there and see. These guys sure take the time to solve a problem! I was amazed at what I saw.

They demonstrated to me how badly the drag link was worn. Wow! Inner tie rod ends were bad, too. Idler arms out of spec. Steering damper shot. They said the shocks were original and should have been replaced 100,000 miles ago. Outer tie rod-rod ends were OK, but should be replaced with the other components. They said that all these factors add up to cause vibration and looseness. We spend an hour looking under the car discussing it. Written estimate for the work= $1,170 (that includes $450 labor and alignment). They did not charge me for what they did today. I felt as if these people were being very honest and straight with me. But you guys know more about this than I do so here's the big question: Does that sound about right or is that high? Should I have the work done or is it just throwing good money away on a high mileage car?

scurling
06-09-06, 12:11 AM
I don't think the problem is with the wheel/tire assembly. The vibration Tim describes is not due to tire or wheel out of balance or out of round. A wheel bearing doesn't usually cause a vibration without other signs of failure. I was really hoping for the axle to be the issue. Aside from that, I would have to revisit the front end linkage components.

Tim:

I thought you had checked the front end and it was ok? You may feel obligated at this point, not to say the car doesn't need the work. The problems you described are normal wear areas that could easily need repairing after 100+K, especially with lax maintenance. My lower ball joints were shot at 45K when I bought my first Fltwd. because the previous owned never greased them.

You could easily spend $450. on the parts you described. The balance of the $1,170 seems a little high for labor. If that includes the balancing work, the price sounds more reasonable. Does the $720. balance include a wheel alignment (generally about $75.00)? If so, the price is getting reasonable.

If you plan to keep your car for a few more years, it sounds like money well spent. Believe me, you will feel the difference with a new front end.

Timothy60
06-09-06, 07:03 AM
Scurling:
Yes, TWO other reapair shops said the front end was OK! One said it was "OK for now" and the other shop said if felt "tight". I went on those recommendations. I checked the front end myself based upon the ideas people presented in this thread, but I am not a mechanic, so I can only look for real obvious things. But the repair shop I went to yesterday said those other places were simply wrong in their diagnosis of the Fleetwood's front-end. They were able to show me the wear in the components. The other places just told me. And I trusted them to be correct. They were not.
Yes, the $720 includes alignment and wheel balance on the Hunter Road Force machine, too. Should I shop around for a better price? There is NO WAY I can do this work myself, although I have installed new rear air bag struts on a 1994 Lincoln Continental. This job seems very complex and best suited for a professional.

Timothy60
06-09-06, 08:27 AM
VIBRATION PROBLEM SOLVED.

I just drove 33 miles to work with absolutely no vibration for the first time since April 10th! This is amazing.

I went out into the garage late last night and pulled the 20 amp fuse for the level ride compressor. Usually when I start the car in the morning, the compressor kicks in and the "level ride" light comes on for about 2-3 seconds. The car must drop down a bit overnight. But this morning, the compressor couldn't pump it back up to trim height, could it? So it rode a bit lower than usual. Absolutely NO VIBRATION on the way to work!

So. . . this is my theory! On April 10 when I had my snows removed, the guy at the tire place must have raised the Caddie up on the lift very quickly and the weight of the rear axle must have banged the ride level adjustment arm just enough for it to cause the back end of the car to raise itself to higher than usual trim height. This caused the geometry of the u-joints and driveshaft to be changed in such a way as to cause vibration. Well? What do you think????

Now how do I adjust that level ride arm back where it should be? Help me out on this one because we almost have this problem solved for good!

scurling
06-09-06, 12:36 PM
Tim:
The back end/body is completely isolated from the drive components. Obviously something changed when you lowered the back end an inch or two. Most likely with the change in weight distribution, the vibration was reduced, and weight is an integral part to vibrations and their causes. Have you returned the back end to normal ride height to see if the vib. returns? A good test to confirm the weight theory.

As far as the repair work on the front end, you could probably do all of that yourself. It's all mechanical work... nuts and bolts, but there are some tips that folks here could pass along before you start. You would need the basics, jack and jack stands, etc. You would also need to get the wheel alignment immediately, before you drove any place. I don't know what your skill level is. Myself, I'm slow, and usually find a few other things to fix or clean whenever I get into a job like this, so I would usually set aside the entire day for a job this size, with a trip to the wheel shop late afternoon or the next morning for the alignment.

Also, it never hurts to get another estimate on the repairs.

Timothy60
06-09-06, 01:39 PM
Scurling:
So the trim height would not change the driveshaft/pinion yoke angle? So it must be that in lowering the trim height about an inch merely redistributed the car's weight in a different way thus changing the dynamics of the vibration. The air shock/spring assemblies control the heighth of the body from the road, not the angle of the driveshaft. OK. I'm getting quite an education.

Well, so much for that theory! That leaves the front suspension again. I'll replace the fuse to the compressor for the ride home and see what happens.

About replacing all the steering linkage components myself. . . well, I think this is where I draw the line. Last year I replaced the 4 airbag struts on my wife's 94 Lincoln Continental. People said, "Don't do it. You'll be sorry." The mechanical R&R wasn't so complex, but removing nuts and bolts that have been on for 10+ years was very, very difficult. I got the job done though, and saved a bundle in labor costs. The work did nothing for marital bliss because what I told my wife would take a Saturday afternoon took all weekend!

In looking at the Fleetwood I see that it's going to take expertise that I don't have. If I screw up, I don't have a car to go to work. I understand what you are saying, but a man must know his limitations. This is one such case!

scurling
06-09-06, 02:39 PM
I understand what you are saying, but a man must know his limitations. This is one such case!

:histeric:

Yes, I know how the wife can get a little edgy when car repairs don't go exactly according to plan. They look at it as though it were yet another project incomplete. One idea is to show your wife the repair quote, and when you do the work yourself, give her half the quote price to go shopping. ;)

If you get the shop to repair your front end, take it to the guys you trust. That's have the battle these days. If you have found a shop that does good work, and treats you right, that's a good combination.
Early on when I got my '94 FWB I had a shop do a "factory" tuneup. I had been going to this shop for years. When I picked up the car, the owner basically (and stupidly) admitted to overcharging me for the GM parts. I haven't been back since.

BluEyes
06-10-06, 12:37 PM
So the trim height would not change the driveshaft/pinion yoke angle?

Yes, it will. The axle stays on the ground, while the transmission moves as it is mounted to the body.

How high up was it in the rear? I'm no driveline expert, but how much of a ride height change would it take to mess up the u-joint angles?

Of course, do retest by putting the fuse back in and seeing if the vibration returns.

If you are satisfied that the vibration is caused by the trim height being off, the ride sensing link should be adjustable. Of course, you would want to properly measure the trim height and adjust it as per the FSM. For that, either pick one up off ebay or see if one of the members here has one that covers your car and if they could scan/transcribe the instructions.

scurling
06-10-06, 02:32 PM
:o Yes, I stand corrected, BluEyes is exactly right. I was focusing too much on the front end.

So, that said, I've posted the Trim Height pages for a '94 FTWD from the FSM. Hope this helps. There are two pages, the first is a short verbage description, the second is the trim height chart and diagrams.


http://members.cox.net/scurling/Trim%20Height%2094%20FTWD.jpg
http://members.cox.net/scurling/Trim%20Measurment%20Chart%2094%20FTWD.bmp

WMD
06-10-06, 03:28 PM
How is the transmission mounted to the body? My transmissions are all mounted to the engine and the frame of the car.
WMD

Timothy60
06-10-06, 07:33 PM
Very interesting developments here. I copied Scurling's information from the FSM. So. . . trim height is something worthy of investigating. By the way, I replaced the fuse for the compressor before I drove home yesterday and guess what? Vibration returned. I estimate that the body drops down about 1/2 " or so if the compressor is de-activated. When fully pumped up, the back end sits about 1/2" too high. I think we're on to something. Would an offset of 1/2" cause the driveline geometry to change enough to induce a vibration? (What happens to those vehicles whose factory trim height is intentionally modified by their owners? Do they have vibration, too?) Now I must resolve 2 important issues:

1. I need to find out how to adjust the level sensor link to factory trim height.

2. Decide if I want to spend $1,170 on the front end if that's not the immediate cause of the vibration.

3. Maybe both?

scurling
06-10-06, 10:52 PM
WMD: Correct, they are mounted together attached to the frame on flexible (rubber) mounts, but the geometry is basically fixed. Now pick up the rear end of the car (frame, and all), which will pivot on the front wheels, and the engine/trans assembly moves with it. THis changes the angle of longitudinal axis running [almost] parallel to the drive shaft, because the rear wheels, axle, etc. which are attached to the drive shaft, stay on the ground. Remember, the drive shaft ends can slide in and out of the transmission and rear differential housings allowing this rear end movement. Keep in mind, we are talking about only a few degrees of movement, but if the shop manual includes the trim height topic in the diagnostic list for vibration problems, we must consider it as a possible cause. Especially, since Tim has conceivably eliminated so many other problem areas.

This issue has got me so involved, I almost feel like pumping up my ride level system to "higher than normal" to see if a vibration is induced. I start my workweek tomorrow, so that may take me a few days. I will have some air tube plumbing to reconfigure, and I'd like to take trim height measurements as I go.

WMD
06-11-06, 09:12 AM
Scurling
I fully agree with you and if raising the riding height again brings on the vibration the Leveling System will have to be corrected. It could have been knocked out of wack on the lift during the snow tire removal. I am also thinking that if this angle and height IS the problem, the car must have looked grotesque if the drive shaft and U joints couldn't handle it.
WMD

Timothy60
06-11-06, 10:02 AM
Scurling, that is an interesting idea to see if you can induce a vibration in your Fleetwood. WMD, the car did not look grotesque, in fact the extra 1/2" or so of added heighth is hardly noticeable unless you lived with this car on a daily basis and would notice a thing like that. That's why it surprises me that such a small amount of lift could cause such a big problem, unless of course the driveline vibration is amplified by worn front-end components and anemic shocks. Also as Scurling pointed out, a change in the trim height might also reduce the weight distribution to the front-end.

BluEyes
06-11-06, 11:33 AM
How is the transmission mounted to the body? My transmissions are all mounted to the engine and the frame of the car.
WMD

d'oh! I guess half mine are, half aren't (mounted to the body that is), but I should have known better on a FWB...

I too find it interesting that just 1/2" higher ride would cause a vibration, but here it is.

Worn out rear shocks would make a vibration worse. At least on my SDV, the rear shocks are mounted at an angle. This was done by Caddy to help dampen side-side axle motions as well.
Did the shop also check out the rear controll arm bushings and their mounts? It is unlikely on a car as new as yours, but worn out bushings would also make a vibration worse. They might also allow the axle to be slightly angled or rotated from where it should be, which could make your u-joint angles worse. Another possibility is that one of the controll arm mounts (or an arm itself) got 'tweaked' by the tire shop as well.

Dunno what do do about the front end work. Personally, I would do it myself as it isn't that hard (except possibly the pittman arm) basically an unbolt and replace operation. Going through rockauto.com those parts cost a laughable fraction of your quote. Of course, I have back-up cars to drive come monday in case I work slowly. :)

Junkman
06-11-06, 03:56 PM
With new universals and a balanced drive shaft, there should be no difference in the ride hight causing a vibration. I am wondering if when they replaced the universal joints, that they might have gotten the drive shaft out of phase? I know on my 1978 Commercial Chassis, the end yoke on the differential has a lot of different holes that you can bolt it up to, but I don't know the reasoning for this. I just made sure that mine went back into the original holes when it was repaired. Possibly if your is like mine, it could have been mounted incorrectly. Junk....

Timothy60
06-11-06, 08:59 PM
Well, this has been quite a learning process about vibration and its causes. At the very least we know that vibration is extremely difficult to diagnose even with a relatively simple drivetrain as on the Fleetwood. I wish to thank all the people here who have made suggestions and offered ideas. They were all appreciated. But this can't go on forever. After much thought, I've made an expensive decision to have the front end done as described in my previous post on Friday. I'm hoping that will restore the car to it's original smoothness or at least minimize the vibration. Those technicians seem to know what they are doing and they took the time to diagnose the problem. They drove the car twice. They inspected, examined, measured, and asked me lots of questions. It almost seemed as if they care. I know they are going to make money from me. I just want my car fixed. If they can do it, then they deserve to have some of my hard-earned cash.

Tonight I brought my Cadillac to the repair shop so they can get started on it first thing in the morning. Put the keys in the drop box. I climbed into the 2006 Dodge Caravan and noticed the silent, patient look on my wife's face, and thought, "This van isn't so bad after all."

N0DIH
06-12-06, 04:07 PM
You can adjust the link between the rear axle and the body to adj height.

Timothy60
06-14-06, 09:32 PM
OK, ready for this?

Picked up my car yesterday from the repair shop. The good news: the bill was less than the estimate! Total cost including tax= $1160
New:
1. drag link
2. inner & outer tie rods
3. shocks
4. idler arms
5. alignment
6. Hunter Road Force Balance

They found one of my new Kelley-Springfield Navigator Gold tires to be faulty according to the Road Force machine. I went back to the tire place and they put on a new one.

With me so far? Now for the bad news: It still vibrates. This is so funny! It's like a joke! I think I'm starting to dislike the Fleetwood. As a matter of fact, my feelings right now are that I'm going to run it into the ground, not put anything in it but gas, and then send it to the crusher at Roth Scrap Metal on Hiawatha Boulevard next spring.

Whatever happened to it on April 10th, 2006 is a mystery to me. That's the day I had my snows removed. That's the day the vibration started. All 4 mechanics I've been to don't really know what's causing it. They think they do, they replace components, but nobody really knows. Is the Fleetwood that complicated? Come on; this isn't a rocket ship! It's a basic RWD American car!

Junkman
06-15-06, 08:27 AM
OK, ready for this?


Whatever happened to it on April 10th, 2006 is a mystery to me. That's the day I had my snows removed. That's the day the vibration started. All 4 mechanics I've been to don't really know what's causing it. They think they do, they replace components, but nobody really knows. Is the Fleetwood that complicated? Come on; this isn't a rocket ship! It's a basic RWD American car!

A thought came to me a few days ago, but I held off posting since you felt that it was still involved in the front end.

My belief is that the harmonic balancer has shifted and is no longer in balance. For those that are not familiar with this item, it is a large disk that is bolted to the crankshaft that consists of a inner steel ring and a outer steel ring, that are held together by a rubber membrane. It is designed to absorb vibrations from the engine assembly that develop from the turning of the crankshaft. They usually have a line stamped across the two halves so you can tell when the rubber has failed. I have seen where sometimes this mark isn't there. You need to remove the balancer to check it properly. If the balancer has spun, then this will cause a vibration. Refer to the shop manual for directions, but going from memory, there are 4 bolts that hold it to the crankshaft pulley. The bolt pattern is staggered so it will only go on one way. Below is a picture of a Chevrolet harmonic balancer showing the mark. Junk

BluEyes
06-15-06, 09:59 AM
With me so far? Now for the bad news: It still vibrates. This is so funny! It's like a joke! I think I'm starting to dislike the Fleetwood. As a matter of fact, my feelings right now are that I'm going to run it into the ground, not put anything in it but gas, and then send it to the crusher at Roth Scrap Metal on Hiawatha Boulevard next spring.

Wait, I thought the vibration had left? Is this that it is still vibrating with the level ride fuse in or out?

If you are serious about crushing it, I will pay you the scrap fee (+ some small percentage if you wish) next spring and gladly come take the car. (I'm an automotive exorcist, haha)
No, seriously, I'll be graduating in May 2007 and I WILL come get the car if you are serious about crushing it. IF you are serious, hit me off-list at djohnson1981@yahoo.com

Timothy60
06-16-06, 08:32 AM
My belief is that the harmonic balancer has shifted and is no longer in balance.

Junkman,
If the harmonic balancer has shifted, would the engine have unusual vibrations at idle or when revved at a standstill?

The Ape Man
06-17-06, 10:22 AM
If the harmonic balancer is messed up then the vibration (if it takes place at cruising speed) will take on a different personality by downshifting to a lower gear. Also check for a siezed clutch on the radiator fan if your car has one of these. Another goofy one is a broken transmission mount. Another really weird one is lack of tension on the fan belt(s) causing the slack side of the belt to fwap around at specific engine speed and accessory loads. Don't replace any more parts without a diagnosis by someone who is competent. Most repair places are in business to sell parts and labor and not to fix your car.

N0DIH
06-17-06, 12:12 PM
Exactly, goes back to, is it rpm dependant or not?

I fought a BAD vibe on my T/A and found the engine to trans bolts loose. That sucked. Tightened and never to return.

Didn't ride height play a factor? Disc compressor and remove air line and drive, see if vib is there. If so, check driveline angles. Is the rear end cocked in the car? Is the trans mount bad and trans moving around? Remember, for every action is an equal reaction. You put power in something, there has to be a return path the source of the power. Cyl heads to pistons to crank to converter to trans to driveshaft to rear end to control arms to frame to motor/trans mounts to block to head bolts to heads....

Does it do it with AC on and off?

With the LT1, remove the belt and isoalte as Ape said. You can run w/o belt.


If the harmonic balancer is messed up then the vibration (if it takes place at cruising speed) will take on a different personality by downshifting to a lower gear. Also check for a siezed clutch on the radiator fan if your car has one of these. Another goofy one is a broken transmission mount. Another really weird one is lack of tension on the fan belt(s) causing the slack side of the belt to fwap around at specific engine speed and accessory loads. Don't replace any more parts without a diagnosis by someone who is competent. Most repair places are in business to sell parts and labor and not to fix your car.

N0DIH
06-18-06, 03:01 PM
From 454ss.com
"U-joints. The rear ones go out most often. Usually this is on a truck that has been lowered. If the operating angle is different for the two u-joints, the driveline will resonate or vibrate at certain speeds. Sometimes under load, sometimes on decelleration. If your truck is lowered and you are using up u-joints, think about adding some 2 degree shims added to the spring bundle to drop the front of the differential down and regain the correct u-joint relationship."

If your upper control arm bushings in the rear are shot, this could lead to problems. I'm not saying U-Joints, but am indicating that the ride height if too high with worn bushings may have put the driveline angles exceeding design limits, aka, Tolerance Stackup. So there is limits in the pinion angle, limits in the driveshaft angles, limits in the rear axle thrust angle, limits to the transmission angles and if they are all at a stackup condition, something goes nutty....

Junkman
08-16-06, 11:19 PM
I was just wondering if the problem ever had a resolution????? Inquiring minds want to know....... Junk.....

Timothy60
01-31-07, 10:57 AM
Yes, there is a resolution, and a positive one at that. It's been a while, I know, but so many people here offered good advice that I thought I owe you a final chapter in the vibration saga. So here goes: After replacing inner and outer tie-rod ends, drag link, steering damper, front shocks, new tires, new u-joints, drive shaft balancing, road force balancing of wheels, wheel bearing repack, and new rear air shocks (ACDelco), the vibration was still present.An unexpected and unintentional event happened back in November that made my Fleetwood feel as silky smooth as the day I first drove it.Here's what happened:I bought 2 used rims from a local auto wrecking place. They were from a 95 Chevy Caprice; standard black steel rims, nothing special. Then I had my Michelin Ice-X snow tires mounted and spin balanced on these ugly rims for winter service. I removed the Fleetwood's back wheels and installed the snow tires. I never even considered that this would make any change but I couldn't believe it when I took it out on the highway: ABSOLUTELY NO VIBRATION AT ANY SPEED.In conclusion, when a vague issue like vibration crops up, it is very difficult for a professional (let alone an amateur mechanic) to diagnose. There is a massive temptation and pressure to remove and replace suspect components at great cost and frustration. I think that my Fleetwood is a better car now that I have made many improvements and I'm glad I did all that stuff. It steers and rides like new. However, none of those repairs adressed the original vibration issue until I put on those snow tires. OK, so now the car is vibration free as long as I have my snow tires on. What should I do in the spring? May I assume that at least one of the original Fleetwood alloy rims has some sort of defect in it that caused the vibration in the first place? What sort of defects affect rims?A common saying amongst doctors is, "When you hear hoofbeats, don't automatically assume it's a zebra." Maybe that applies to owning a Cadillac Fleetwood, also.

BCs71
01-31-07, 01:15 PM
OK, so now the car is vibration free as long as I have my snow tires on. What should I do in the spring? May I assume that at least one of the original Fleetwood alloy rims has some sort of defect in it that caused the vibration in the first place?

If you have bad wheel(s) then I would first make sure a competent person balanced them properly. When the rim is on a balancing machine, you can see it spinning from many angles. Usually the machine has a small arm or pointer that you can hold against the rim as it spins. If the rim is oblong then the pointer will skip across the surface.

SInce you already replaced tires then I would assume on of those rear wheels (or both) are bad somehow. This is assuming they were balanced properly. Factory wheels generally get balanced very well using weights on both sides.

Congrats on finding the problem!
I once bought a set of wheels and tires that each had problems. They each caused vibrations. Eventually I got rid of the wheels and mounted the tires on stock rims instead, and then discovered that the tires themselves cause some minimal vibration. Very annoying! :thepan:

N0DIH
01-31-07, 02:40 PM
Have a tire shop check wheel runout and check for broken belts. Also, a friend of mine with a 96 Deville wrong wheel drive had a cracked rim that was causing him problems. The shop welded it up, but it leaks air now....

(anyone have a chrome 94-96 Deville wheel laying around?)

Hammondsix
01-31-07, 05:02 PM
I have a situation much like yours. Maybe My problem is the rims as well.

BluEyes
02-01-07, 06:44 AM
Wow, I'm surprised that the tire shops didn't catch that earlier. The place I go to checks the rims every time they do tires. Of course, proof will be after checking rim runout and concentricity. Should only take a few minutes since the rims are off the car already.

Does your car run alloys or hubcaps? If it's hubcaps, some don't attach as well as others and can cause a vibration that might seem like it is the rim.

N0DIH
02-01-07, 02:53 PM
I had a 91 Lumina that I ran too high air pressure (50 psi on 195 75 14's) running it hard and went over some RR tracks and it broke a belt. Drove goofy. At slow speeds it would turn the wheel slightly if you let go of the wheel. Look for the tread lines to not be in line, or a "bump" in the tire when looking across the tread from the side. Any tire shop worth its weight in salt should be able to catch that fast.

Sams often does stuff for free, and catch them when they are bored on Sunday morning or later evening. The guys are looking for work to do....

ReagansRollsRoyce
02-01-07, 03:43 PM
I had similar problems too, for just about as long as you...I, too, replaced the shocks, the links, the transmission mount, had the driveshaft inspected.

Turned out to be

1. Tie rods, which, amazingly, Town Fair Tire found despite my taking several trips to high-rated mechanics and them not finding it.

2. Wheels themselves, also found by Town Fair Tire. They claimed that the last person who had changed my tires had over-shot the lug nuts. They said in the future I should include specific instructions that only hand-torquing of the nuts be allowed.

I had no idea whether to believe them, having already spent about as much as you have on repairs, but those two efforts solved my problem, it seems.

The problem that sagas like yours (and mine) have caused for me is trust in repairmen. I can't do much more than change the oil and fluids...I've followed friends recommendations for mechanics, gone to people who get high ratings in the paper, etc. Yet Town Fair Tire is the place the finds the problem, a problem they aren't even able or trained to fix...and yet that turns out to be the correct diagnosis. Makes you wonder...