: 4th Gear Grind, Clutch or Trans Issue ?



SevillianSTS
07-16-12, 07:44 AM
I originally posted this in a different thread, decided to erase that one and start a new one.

I was out on some back Michigan roads, ran her up to 5500 - 6k on the tach and when I shifted(pretty quick) to 4th I got a slight grind, twice.
Trans now has 1000 miles on it.
They also put in a new slave cylinder when they did it... which means the clutch fluid was also flushed. (Nice and clean)
I ran it again and waited a second between shifts and it was fine, but thats no good if I'm trying to get my best time, etc...
I can quick shift through 1,2,3 just fine.

Would this be a problem with the new transmission, or a clutch problem ?

FuzzyLogic
07-16-12, 10:36 AM
I'll say it: sounds like driver error.

When you let off the clutch at 6000 RPM, the abrupt torque reversal might be making your foot bounce on the clutch pedal as you enter the 4th shift gate. That, or you're letting off the clutch before the syncros are done.

SevillianSTS
07-16-12, 02:17 PM
I'll say it: sounds like driver error.

When you let off the clutch at 6000 RPM, the abrupt torque reversal might be making your foot bounce on the clutch pedal as you enter the 4th shift gate. That, or you're letting off the clutch before the syncros are done.

I have run it up through 4th plenty times before and never had this happen; and BEFORE the transmission replacement. I've been pretty easy on it for a while now for the new trans to break in. I have no problem 1-2 or 2-3 and yet "3-4" is the easiest of all shifts. :hmm:

FuzzyLogic
07-16-12, 02:22 PM
Do you know what kind it oil viscosity you're running now versus before?

SevillianSTS
07-16-12, 02:38 PM
whatever GM fills it with for a new trans

SevillianSTS
07-16-12, 02:58 PM
I had mobil1 on synthetic ATF before

SevillianSTS
07-17-12, 07:22 AM
Today I tried shifting hard / quick from 3 to 4 at around 4000 rpm and had no grind.

Seems like this problem should have a straight forward explanation, clutch or trans; I'm still learning on this stuff though. Anyone have any advise.

Thanks.

Cadillac Cust Svc
07-17-12, 08:27 PM
SevillianSTS, it looks like you're seeking DIY input from other owners. So, I just wanted to let you know I'm available to assist if you decide to consider the dealership route at any point!

Looking forward to the thread updates,

Katie
Cadillac Customer Service

SevillianSTS
07-18-12, 06:22 AM
I have spoke with the dealer about this, I was waiting for a little feedback on here before I take it in though.

I tried again on my way home this morning powershifting at a lower rpm, probably around 4k and there is no grind.

OneFast V
07-18-12, 06:12 PM
if its only going into 4th gear and not any other gears... then it's most likely transmission related..

Scott2012
07-19-12, 10:12 PM
if its only going into 4th gear and not any other gears... then it's most likely transmission related..

Ditto, synchro, my guess

stepchild21
07-20-12, 01:14 AM
My cars doing that exact thing, for me my third gear synchro is pooched !!!!!! Tranny rebuild time for me coming up next month.

SevillianSTS
07-20-12, 06:02 AM
Ditto, synchro, my guess

Even with the fact that its a new trans with 1000 miles on it... driven pretty easy so far ??

darkman
07-20-12, 07:55 AM
I understand that the clutch fluid is fresh but, have you checked the level since completing the break-in period?

SevillianSTS
07-20-12, 08:31 AM
Ok, just got home and was out in-between some corn fields. Figured I would do some more testing on this...

Darkman: fluid level is full, and still clean looking.

With the new trans in: I have never had a problem powershifting from 1st to 2nd.

Today: I had it grind as it went into 3rd a few times, NOT every-time though.
It does grind EVERY-time I powershift into 4th..

I originally thought it was just 4th, but after today's testing 3rd does sometimes.

Being I am testing on this issue, I have been making absolute sure that I mash the clutch all the way in also.

So.... on my way home I stopped by the dealer to question this. Being you have to be going about 80 to get into 6k rpms in 3rd gear... dealer says nothing he can do because they will not break the law ( I do understand this, but our by-pass is like 5 minutes away and the limit on there is 65-70)
I think I'm officially done with them... Next choice is not that much further away.
I did not mention 2nd to 3rd shift to them because I never tested that gear real hard until after I left the dealer, and since that seems more intermittent you know how that will go over with them.

Anyways, before I crawl under the car and do the dreaded clutch fluid bleed.... Is it possible that an air bubble could be causing this. As long as you are not close to red-line it does not grind.

I NEVER had these problems until the new trans was put in, and they did replace the slave at the time of the new trans.

So I essentially have a performance sedan that I can NOT drive like a performance car

darkman
07-20-12, 08:47 AM
The problem may very well involve the transmission synchronizers but the Service Manual troubleshooting procedure for shifting problems seeks to eliminate clutch drag first, before looking to the transmission. The checklist in the Service Manual for clutch drag is as follows:

1. Pedal blocked from full travel.
2. Too much travel between pedal and clutch master cylinder or worn pedal bushings.
3. Clutch pedal mounting loose.
4. Linkage at pedal worn or damaged.
5. Clutch master cylinder is seized or binding.
6. Air in clutch hydraulic system.
7. Clutch actuator (slave) cylinder seized or binding.
8. Clutch master cylinder leaking internally.
9. Damaged clutch assembly components. This includes damaged clutch disc, hub,splines, bent clutch disc, bent drive straps, broken or warped pressure plate.[I did not find any thickness specs for the clutch disc.]
10. Excessive side loading on the release bearing.
11. Faulty pilot bearing.
12. Transmission input shaft splines are worn or damaged.
13. Tight or contaminated clutch disc splines.
14. Flywheel housing, engine block to clutch housing, or transmission frontcase excessively misaligned.
15. Grease or oil contamination on the clutch disc facing.
16. Loose, broken, or faulty motor mounts.

See also the attached.

SevillianSTS
07-20-12, 09:11 AM
1. Pedal blocked from full travel. Wouldn't this cause a problem in all gears, and not just high rpm shifts.
2. Too much travel between pedal and clutch master cylinder or worn pedal bushings. How likely is this, and how do you test it?
3. Clutch pedal mounting loose.
4. Linkage at pedal worn or damaged.
5. Clutch master cylinder is seized or binding.
6. Air in clutch hydraulic system. I'll do a bleed to eliminate this.
7. Clutch actuator (slave) cylinder seized or binding. Is it possible for a new one to do this ?
8. Clutch master cylinder leaking internally. ??
9. Damaged clutch assembly components. This includes damaged clutch disc, hub,splines, bent clutch disc, bent drive straps, broken or warped pressure plate.[I did not find any thickness specs for the clutch disc.]
10. Excessive side loading on the release bearing.
11. Faulty pilot bearing.
12. Transmission input shaft splines are worn or damaged. Brand new trans; I beleive, if not it was manufacture refurbished.
13. Tight or contaminated clutch disc splines.
14. Flywheel housing, engine block to clutch housing, or transmission frontcase excessively misaligned. I could see this being a dealer error, but high rpm only makes me think this isn't the case either.
15. Grease or oil contamination on the clutch disc facing.
16. Loose, broken, or faulty motor mounts. Brand New stock mounts.


Thanks Darkman.

SevillianSTS
07-20-12, 09:31 AM
I guess some quick info would be:

No grind if I powershift at less than high rpm.

No grind if I delay my shift at high rpm

I want to blame the clutch, but the two above facts make me think otherwise.


Grinds powershifting into 3rd at high rpm sometimes

Grinds powershifting into 4th at high rpm everytime.

CadzillaTN
07-20-12, 10:08 AM
Bleed bleed bleed that clutch.


Or, just keep powershifting until something else breaks.

Scott2012
07-20-12, 12:02 PM
Even with the fact that its a new trans with 1000 miles on it... driven pretty easy so far ??

Its rare with miles that low but not impossible. Unless you have low fluid, I'm gonna guess it'll need to be dropped and opened... But, ya never know, maybe it'll be something simple. :)

SevillianSTS
07-23-12, 08:58 PM
Third gear is still intermittent... sometimes it shifts smooth, other times it'll grind too.

I tried double clutching going into 4th a few times and it still grinds a little, more of a slight chirp instead of a full-out grind.

Does that narrow it down at all ?

stepchild21
07-24-12, 12:42 AM
My uncle works for gm hes their shop Forman. He came for a ride in my 04 V ( which is having the same problem) and he told me my 3rd and 4th synchro is shot.


I just find it od how you just had it rebuilt and it's doing this.

Sorry im new here but did you personally rebuild it, or was just told the the tranny was rebuilt when you bought the car?

SevillianSTS
07-24-12, 06:16 AM
dealer replaced it under powertrain warranty. Not sure if its factory rebuilt or new.

darkman
07-24-12, 06:58 AM
dealer replaced it under powertrain warranty. Not sure if its factory rebuilt or new.

What is the type and age of the clutch/flywheel?

SevillianSTS
07-24-12, 02:09 PM
Clutch and FW are both stock. 77k miles.
It does not slip at all, I got up to 55, rev'ed engine close to 5k and let off clutch and the tach jumps right back down pretty quick.

darkman
07-24-12, 02:22 PM
Clutch and FW are both stock. 77k miles.
It does not slip at all, I got up to 55, rev'ed engine close to 5k and let off clutch and the tach jumps right back down pretty quick.

Clutch drag at high rpm, and not at low rpm can have to with the hydraulics, but it can also be a failing pressure plate (metal fatigue). You could test for this by seeing if the car wants to lurch while parked on level ground in gear when the rpm is increased to something like 5,500 rpm with the clutch pedal held on the floor. (Make sure the engine is at full operating temperature.)

SevillianSTS
07-24-12, 04:33 PM
Clutch drag at high rpm, and not at low rpm can have to with the hydraulics, but it can also be a failing pressure plate (metal fatigue). You could test for this by seeing if the car wants to lurch while parked on level ground in gear when the rpm is increased to something like 5,500 rpm with the clutch pedal held on the floor. (Make sure the engine is at full operating temperature.)

Just rev it with the shifter already in gear, or put into gear while the rpms are high ?
Also which gear should I leave it in when trying this ?


I do feel the car "pulse" very slightly when pushing into any gear, it doesnt want to pull away just the pulse, it did this with the old transmission also. So I then lifted the rear and the tires never moved as I put it in gear.

darkman
07-24-12, 04:47 PM
Just rev it with the shifter already in gear, or put into gear while the rpms are high ?
Also which gear should I leave it in when trying this ?

It should be already in 1st gear, clutch to floor, level ground, no brakes on. The idea is too see if clutch drag sets in as the rpm increases. It the clutch is dragging the car should start to move.

SevillianSTS
07-24-12, 05:17 PM
It should be already in 1st gear, clutch to floor, level ground, no brakes on. The idea is too see if clutch drag sets in as the rpm increases. It the clutch is dragging the car should start to move.

Damn she sounds good with the borla and backed into the garage at 5k :cool:

Anyways... car does not move at all, I had it in 1st park brake off and 5k and maybe even a little more.
I even tried reverse being it had a lower gear ratio. (kinda nervous, but it didn't move)

I get the pulse or initial bump when pushing into gear, but car never moves while in gear and at high rpms.

Darkman, do you think this is leaning towards the trans now ?


Its going in Thursday to a different dealer... and yes they seemed much more pleasant.

darkman
07-24-12, 05:29 PM
If you cannot confirm any symptoms of clutch drag, it comes down to the transmission.

Frankly, if it were mine and I lived anywhere close to RPM Transmission (Anderson, In) I would take it to them diagnose it. If they had to pull the transmission I would have them upgrade the clutch at the same time based on the number miles on it.

SevillianSTS
07-26-12, 10:37 AM
Just got back from dealer #2 They are much more pleasant to work with.

I took him for a ride and showed him how I could have the rpm's up and shift into 2nd and 3rd fine (seems very seldom that it grinds into 3rd now), and then got to 5900 rpms and it grinds into 4th. I did not launch the car, I just got on the highway and drove the gears up to the high rpm's before shifting.
At 5900 rpm's it gives a mild grind, and if you get up to 6200 its a pretty violent grind.

He commented on how this is not everyday driving, and I understand, but it still shouldn't do this. He said this would be hard for his tech to diagnose being it has to be into high rpms. He said I should wait and see if it gets worse to where it affects everyday driving and then come back.


Darkman, I looked at RPM Transmission's site, and if I did not have warranty on the car I would definitely go there. I'm just trying to utilize the warranty while I have it.


So now I have to just "deal with it" until it gets worse. I do not like the thought of that at all.

Any last thoughts on this ?

darkman
07-26-12, 11:52 AM
Darkman, I looked at RPM Transmission's site, and if I did not have warranty on the car I would definitely go there. I'm just trying to utilize the warranty while I have it.

So now I have to just "deal with it" until it gets worse. I do not like the thought of that at all.

Any last thoughts on this ?

I would be tempted to take it to a Chevrolet Dealer. My local Chevy Dealer sent a flyer once that indicated that they would do warrantly work on any GM vehicle. If you have a local Chevy dealer that does that they may be better qualified to deal with your problem since they have more exposure to high horsepower Tremec applications (Corvettes) than Cadillac dealers.

Beyond that, I suspect your current clutch will not last much longer given its age (mileage) and your driving style (high-rpm powershifts). I also assume that it will not be covered by your warranty since clutches are typically considered a consumable component. If the clutch is removed for replacement the transmission will be on someone's work bench. Perhaps if it were on RPM Transmission's work bench the marginal cost of having them check the synchronizers, blocking rings, etc. might not be too bad. Just a thought.

Good luck.

SevillianSTS
07-26-12, 10:34 PM
I would be tempted to take it to a Chevrolet Dealer. My local Chevy Dealer sent a flyer once that indicated that they would do warrantly work on any GM vehicle. If you have a local Chevy dealer that does that they may be better qualified to deal with your problem since they have more exposure to high horsepower Tremec applications (Corvettes) than Cadillac dealers.

Beyond that, I suspect your current clutch will not last much longer given its age (mileage) and your driving style (high-rpm powershifts). I also assume that it will not be covered by your warranty since clutches are typically considered a consumable component. If the clutch is removed for replacement the transmission will be on someone's work bench. Perhaps if it were on RPM Transmission's work bench the marginal cost of having them check the synchronizers, blocking rings, etc. might not be too bad. Just a thought.

Good luck.

Thanks for all your help.

Unfortunately, both dealers are my local Chevy / Cadillac Dealers.

SevillianSTS
07-31-12, 01:39 PM
Update:
Earlier today I was in 1st gear, got into it probably around 6k on the tach then shifted to 4th and it again grinded real bad.

Didn't know if this would add to the diagnosis since before I always had it do it from 3rd into 4th before ?

darkman
07-31-12, 02:07 PM
Well the 1st to 4th shift does represent a test the dealer can do without breaking any laws and/or shop protocols. Additionally, since the OEM-CAGS "requires" a shift from 1st to 4th, GM can hardly deny that its gear box is supposed to do that as a "normal" operation.

SevillianSTS
08-02-12, 10:42 PM
Always a twist in the story...

So last night (more trial and errors) I ran first up to 6k and then shifted to 4th, it grind'ed pretty bad. Seems ever since it does not grind any more. I tried the same again tonight on the way home and zero grind. Yet, there seems to be no other negative aspects either... all gears shift fine still.

Is it possible that something just needed "wore" in ? 1700 miles on trans now.

darkman
08-03-12, 07:16 AM
Or, just keep powershifting until something else breaks.


Is it possible that something just needed "wore" in ? 1700 miles on trans now.

Sounds like CadzillaTN was right all along.

SevillianSTS
08-04-12, 01:24 AM
Well... since I've been paying so much attention lately... I do think 4th feels more notchy now. Feels kinda what 2nd felt like with the old trans. As I move it into 4th I feel 2 solid clicks, while all other gears are nice and smooth (once all warmed up)