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87K views 252 replies 57 participants last post by  derone 
#1 ·
2001 STS 34,000 miles

My 2001 STS has been back to dealer nine times for this 60-75 MPH Shake/Shimmy. Cadillac zone rep drove the car and said it is OK. This problem comes and goes. after having a tire store balance the tires it lasted 300 miles. Now time to balance again, this game is getting old. Went 300 miles without any problem, now Shake/Shimmy again.


Owned 92 STS and it drove perfect, no shake/shimmy. Also owned a 1997 Concourse, drove perfect too. What did Cadillac do to their front wheel drive. They have replaced the tires (1.5) sets, 6 balancings, front control bushings replaced. Cadillac customer care offered free tires and oil changes for two year. I said "No thanks I just want my car fixed. They said they would continue to work on it. I think Cadillac dealers need special hotels for owners of this Shimmy/Shake problem. They can balance at night while we sleep. The dealers are getting tired of seeing me as they have no solution.

How many thousand Cadillacs are out there that have a Shake/Shimmy problem.

Frank in Dallas texas
 
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#104 ·
Sorry to hear that Dadillac...I know what you are feeling....I replaced all four motor mounts on mine and it did not touch the problem...that is why I think Logan is on the right track with the cradle mounts....that has got to be the problem.....now we just need a resolution.
 
#108 ·
Okay, I ordered the upper mounts from www.gmpartsdirect.com and they are set to be here on Tuesday. Hopefully the new mounts will cure the problem, but, I am thinking ahead a little. As stated earlier, the only cars that seem affected, are cars that do not have dogbones. So, aside from the dogbones themselves, what else does our dogboneless cars need, to retro fit them in there? I have a 2002 Seville, and know for a fact, that a 2002 Eldo, has dogbones. I cannot imagine, that the N* in the two cars is different. So, that would make me assume, that any engine bracketry would just bolt in place. But what about the upper radiator mount? Is it different between the two cars? Can an Eldo mount be bolted to it? Does anyone know the answers to these questions? Thanks in advance.

Don
 
#109 ·
Logan,
Any new resloutions? It sounds like you are on the right track to root the cause. I also would like to retro fit my 99 sts with the up dated sub frame mounts. So far Michellin Tires and Road Force balancing has taken care of 95% of my shimmy/shake.
Frank
 
#110 ·
Don-I can't see any differences on the engines. When you buy the dogbones for an Eldorado from GM, they come with the bracket that mounts it to the radiator support. Whether or not it'll reach on the Sevilles is another story.

I don't know how soft the three oil-filled engine/transmission mounts on the Seville are, but I can tell you that the mount in the back is fairly soft. That's why I keep thinking it's the engine that ampliflies the shake. I mentioned before that one of the board members put a solid racing mount in place of the front mount and he said that the ride improved.

I have a book that GM put out on the '98 Sevilles just before the introduction and it has blurbs in there how the changed the engine mounting to isolate it better and how they used new bushings on the front control arms to absorb wheel deflection over big bumps. Maybe it's a combination of the two that's creating the problem.
 
#111 ·
El Dobro said:
Don-I can't see any differences on the engines. When you buy the dogbones for an Eldorado from GM, they come with the bracket that mounts it to the radiator support. Whether or not it'll reach on the Sevilles is another story.

I don't know how soft the three oil-filled engine/transmission mounts on the Seville are, but I can tell you that the mount in the back is fairly soft. That's why I keep thinking it's the engine that ampliflies the shake. I mentioned before that one of the board members put a solid racing mount in place of the front mount and he said that the ride improved.

I have a book that GM put out on the '98 Sevilles just before the introduction and it has blurbs in there how the changed the engine mounting to isolate it better and how they used new bushings on the front control arms to absorb wheel deflection over big bumps. Maybe it's a combination of the two that's creating the problem.
So the '97 & '98 - newer N*'s have different engine / tranny mounts? Also the Eldo's engine mounts are different? I was unaware of this. The only thing I knew as definites, were the cradle, and the dogbones. Well, maybe I am getting too far ahead. Let me do the upper cradle mounts, and see what happens.

Don
 
#112 ·
agood1...that is why I think Logan is on the right track with the cradle mounts.
Yep.

I just had my tires balanced (as in road-force) and rotated again today. Before this, my vibrations were occurring between 72-77MPH. Now that the tires have been rotated, the range is 70-75. It's still there, it just occurs in a different range.

This appears to be a matter of harmonics and the resonant frequency that will change with regard to change in the balance and rotation of the wheel/tire combination. In other words, it doesn't matter if you're running with the OEM GoodYear Eagle LS' (that gathered a lot of complaints in previous threads) or Michelins (that a lot of us went to as replacements), and it doesn't matter if you have had the tires road-force balanced (as a lot of us had done). The problem may seem to be marginal at times, however it still exists.

Logan is definately on the right track here. It is just a matter of finding the right cradle bushings to eliminate this issue.

Question,

Would it be possible to make replacement bushings out of a material like urethane or UHMW?
 
#114 ·
It had been very mild here in Nashville, then winter came...

So, I have been driving the car with the sockets still trapped in place and the stiffened upper strut mounts. The only problem I have is a pop sound every now and then.

Car has been driving smoother then it ever did before. Its a currently a joy to drive.

I have the solid cradle mounts ready to go.....just waiting for some warmer weather.




Logan Diagnostic
www.airbagcrash.com
www.ledfix.com
www.logandieselusa.com
 
#115 ·
Don,
Can you make a note of the part numbers on the cushions you ordered? I have looked at replacing mine....but I can't get the correct part numbers....

Logan, hopefully you will get some better weather....been pretty nice in Atlanta, but as they say around here. "if you don't like the weather in Atlanta, just wait a couple of days"
 
#116 ·
I had some time after work today, and tried doing the mounts. The upper mounting plate, has a sleeve, that the bolt goes through. I could not get the mount plate off, as the cradle would not drop down far enough. After re-examinimg this, I came to the conclusion, that the upper plate, is most of the problem. The rubber wears, and the lower mount plate, presses on the sleeve in the upper plate. Thus, not having pressure where it belongs, on the rubber mounts. I am going to try and find an appropriate spacer, that I can put between the lower mount, and the lower mount plate. This will distance the lower plate, from the upper plate sleeve.

On a side note, this day is just wonderful. Not only did this project bust, but my windshield cracked this morning. Nothing hit it, it just cracked. So I am getting a new one tomorrow, at a cost of $343.01. SOB. I hope everyone elses day is going better than mine.

Don
 
#117 ·
agood1 said:
Don,
Can you make a note of the part numbers on the cushions you ordered? I have looked at replacing mine....but I can't get the correct part numbers....

Logan, hopefully you will get some better weather....been pretty nice in Atlanta, but as they say around here. "if you don't like the weather in Atlanta, just wait a couple of days"
I posted the numbers on the previous page.

Don
 
#119 ·
agood1 said:
Don,

Are you saying you could not replace cradle mounts....are made into the cradle?
The cradle mounts are as follows. A lower mount plate (bolt goes through it, and lower mount sits between it and the cradle), lower mount bushing, cradle, upper mount bushing, upper mount plate. The bolt goes through it all, and goes into the frame. The upper mount plate (between the frame and upper mount bushing) has a sleeve in it (it is about 3-4" liong, and the bolt goes through it), that makes contact with the lower mount plate. When I lowered the cradle, it only dropped about 3". I loosened the left side motor mount, and the left side strut. This didn't help any. Anyway, I couldn't get the upper mount plate off. The sleeve was still in the cradle, and I needed more room. I couldn't figure out how to get the cradle lower, so I just put it all back together. I am now on the hunt for some heavy rubber, or thick steel, to make a shim, to install between the lower plate, and the lower mount. This will stop the lower plate from contacting the sleeve, and allow the rubber mounts to compress and do thier jobs. I hope this wasn't confusing. I know what i am trying to say, and I confused myself with this.:D

Don
 
#121 ·
Are you guys removing all 6 cradle bolts? I had to replace my steering rack a couple of weeks ago, and I had to remove all 6 cradle bolts. I had the car on a lift and both sides of the cradle supported, but it came down at least 4 inches. That should be enough to get the mounts out......but you will have to remove, or at least loosen all 6 bolts. I tried just the back 4 bolts and it did not move enough for me to get to the rack mounting bolts.
 
#122 ·
I had all three driver side bolts out, and the passenger side bolts loose. I jacked up the car, put a jack stand under the driver side, removed the tire, and the cradle only lowered a little.

I came up with a solution though. I just ordered the lower mount plates today. I am going to enlarge the hole of one plate, so that the upper mount sleeve will not contact it, and install another plate over it. It should give at least 1/4 - 1/2 inch additional clearance. So the plates will squish the rubber with more force. I do not see why this would not work, so I am going to try it. The worst that can happen, is I am out another $21.00, and a few hours of my time. I will post with the results when it is done.

Don
 
#123 ·
Logandiagnostic said:
I also have not found the room to remove the upper mount plate.

I am begining to think the you remove the mount bolts on 1 side....and loosen the mount bolts on the other side. Maybe that will provide enough room...

I also cannot figure out how the lower rubber comes off the cradle....



Logan Diagnostic
www.logandieselusa.com
www.ledfix.com
www.airbagcrash.com
Working in the driveway, the spacer that goes through it has to come out first. Soak the mounts metal collar with penetrating oil where it sticks through the frame. After it sits a bit, place something thick between the mount and the car body and jack the frame up to push the mount out. When I get a real stubborn one, I hack off the part sticking through the frame and pry the rest of it out.
 
#126 ·
It also looks like the rear trans mount was eliminated.

I was screwing around under the hood of my '98 SLS and I had the parking brake off, with the car in park. I pushed up against the car and then let it roll back. When I saw the engine move, I rocked the car back and forth a few times. It was very interesting to see how much the engine moves around when you do that.
 
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