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I'm sure this is an old subject to many of you but I just ran across it, issues involving Torque Tubes. I've been reading through a lot of threads trying to bring myself up to speed on the subject, specially on C7's but I haven't been able to nail down a few things, so I'm hoping those in-the-know can provide some answers. I own a low mileage 2015 C7 M7 Z51. No problems with it so far but I'd like to find out just how common Torque Tube issues are with this generation, and gather as much information I can on the subject, in case I have to deal with it. Any help with these questions would be greatly appreciated:
* From what I've read, there seems two main issues are causing Torque Tube failures, failing bearings which can cause driveshaft wobble with the rubber bushing rubbing and wearing inside the Torque Tube. And also the rubber bushings themselves cracking. Are these the two main causes of Torque Tube failures?
* Are Torque Tube failures to be expected eventually, or is this issue only occurring with a small percentage of C7's? And are there high mileage C7 owners out there who haven't experienced Torque Tube issues?
* I've heard that GM Service Centers will not rebuild a Torque Tube but instead will replace the entire Torque Tube/Drive Shaft assembly, with the cost being around $6k. is this correct?
* Is it correct that Torque Tube issues can occur on both automatic and standard shift C7's?
* I've read that GM Service Bulletins are out on this issue, and one states that changing the metal Stingray and GS Torque Tubes, to Carbon Fiber Z06 Torque Tubes solves the wear problems. Is this correct?
* I've read possible option is to replace the rubber bushings with metal bushings. I'm guessing GM initially used rubber bushings to absorb shock, so would switching to metal bushings be an unwise choice?
* And from what I've read, there is no way to inspect the condition of the rubber bushings without disassembling the Torque Tube (no inspection window on the torque tube). With the vehicle on a Lift is there any other way to check the condition of the Torque Tube bearings or bushings?
TIA
Rave
Last edited by Rave; Nov 2, 2024 at 03:22 AM.
Reason: Addition
I did a complete 4 part Root Cause Failure Analysis on the TT and now I am rebuilding a TT for my Z51 Auto Trans using what I learned. See links below and let me know if your concerns are answered and what you think.
While I don't have any hard numbers, reading the posts here seems to indicate that TT issues are more prevalent on cars which spend more time in V4, and that would be the A8's.
Thank you. Wow, that is a lot of information to digest. Many thanks for all your efforts. From your photos and explanation it seems you are putting more engineering effort into the issue than GM did. Also seems the GM TT design isn't designed for the long term. It would be interesting to know how many C7 owners have had TT problems, but I guess that information may never be known.
I'm guessing GM opt'ed to use rubber bushings to absorb gear shock during accelerating & deaccelerating, and shifting? And if that's the case, I wonder if changing to solid bushings has a negative impact on other drive train components? I can definitely understand where a minimum run out would beneficial, especially for the vibration of the M7 linkage and shifter.
Given the potential for out of tolerance TT run-out to cause expensive damage to the engine or transmission, catching the problem early sounds critical. Then the question becomes, do owners let GM replace defective components with the same components which puts the liability on GM, or do owners take a modified TT path and take on the potential liability themselves?
I wonder if the potential TT issues in the 5th, 6th, and 7th generation is one reason GM opt'ed to a rear engine design in the C8?
Thank you. Wow, that is a lot of information to digest. Many thanks for all your efforts. From your photos and explanation it seems you are putting more engineering effort into the issue than GM did. Also seems the GM TT design isn't designed for the long term. It would be interesting to know how many C7 owners have had TT problems, but I guess that information may never be known.
I'm guessing GM opt'ed to use rubber bushings to absorb gear shock during accelerating & deaccelerating, and shifting? And if that's the case, I wonder if changing to solid bushings has a negative impact on other drive train components? I can definitely understand where a minimum run out would beneficial, especially for the vibration of the M7 linkage and shifter.
Given the potential for out of tolerance TT run-out to cause expensive damage to the engine or transmission, catching the problem early sounds critical. Then the question becomes, do owners let GM replace defective components with the same components which puts the liability on GM, or do owners take a modified TT path and take on the potential liability themselves?
I wonder if the potential TT issues in the 5th, 6th, and 7th generation is one reason GM opt'ed to a rear engine design in the C8?
Rave
The biggest reason for failures is that the rubber couplers do absorb shock, vibrations and runout, that's what kills them and the more the couplers have to absorb runout the faster they build up heat and fail. The bearings typically don't fail they flop around and make noise when the o-rings in the housings fail and lose grip on the outer bearing race and excessive runout and heat cause the o-rings to fail faster.. If you plan to use solid couplers or delete the couplers you would benefit greatly by doing what I have done to reduce or eliminate runout.
Also for a nominal cost I have an open offer to check and optimize all of parts for anyone who doesn't have the means or know how and they plan to rebuild the TT themselves, and I plan to buy more TT off of ebay optimize them and sell them.
The biggest reason for failures is that the rubber couplers do absorb shock, vibrations and runout, that's what kills them and the more the couplers have to absorb runout the faster they build up heat and fail. The bearings typically don't fail they flop around and make noise when the o-rings in the housings fail and lose grip on the outer bearing race and excessive runout and heat cause the o-rings to fail faster.. If you plan to use solid couplers or delete the couplers you would benefit greatly by doing what I have done to reduce or eliminate runout.
I've read that some GM service centers are using Z06 TT parts when repairing GS and Stingray TT's, and this is suppose to resolve future TT issues. I'm guessing the Z06 TT's also use rubber bushings?
I've read that some GM service centers are using Z06 TT parts when repairing GS and Stingray TT's, and this is suppose to resolve future TT issues. I'm guessing the Z06 TT's also use rubber bushings?
Rave
The only TT available from GM is the Z06 carbon fiber TT in their performance parts catalog but still could have excessive runout and fail.
* I've heard that GM Service Centers will not rebuild a Torque Tube but instead will replace the entire Torque Tube/Drive Shaft assembly, with the cost being around $6k. is this correct?
Is this a carbon TT price or metal? I paid around 2k to replace Z51 TT assy some years ago.
* I've heard that GM Service Centers will not rebuild a Torque Tube but instead will replace the entire Torque Tube/Drive Shaft assembly, with the cost being around $6k. is this correct?
Is this a carbon TT price or metal? I paid around 2k to replace Z51 TT assy some years ago.
Typically a dealer or GM Serice Centers and some Independent shop will not rebuild a TT and will only replace TT with a new TT from GM. Some independent shops and Performance Specialty Shops will rebuild and swap out TT. From what I can find out the only new TT available from GM in their Performance Parts Catalog and it is the Z06 carbon fiber TT, I think the price was around $3K.
The most important question is: Will any Dealer, GM Service Center, Independent Shop or Performance Specialty Shop who will only replace TT with a new one make an extra effort to trouble shoot a new TT and measure the individual parts for excessive runout and then take steps to correct & optimize the TT? The correct answer is: Unlikely.
The next most important question is: Will any Independent Shop or Performance Specialty Shops who rebuilt TT make the extra effort to measure, correct and optimize the all the individual parts within the TT, also will they know about Buna-N o-rings vs. Viton o- rings, and will they know about Standard Bearings vs. Non-Contact Seal Bearings, all to give you the best chance of a TT that has less vibrations, noise and will last an extra-long time. The correct answer is: Yes/Maybe, but only if you the customer, the vette owner makes sure the shop is aware of the issues, parts upgrades and how to measure & optimize the TT and you are willing to pay for the extra efforts. I've mentioned many times about the parts having excessive runout, poor surface finishes, and very loose tolerances.
Too often we just trust that the OEM parts are the best regardless, but my findings prove otherwise, so "Trust But Verify"
The biggest reason for failures is that the rubber couplers do absorb shock, vibrations and runout, that's what kills them and the more the couplers have to absorb runout the faster they build up heat and fail. The bearings typically don't fail they flop around and make noise when the o-rings in the housings fail and lose grip on the outer bearing race and excessive runout and heat cause the o-rings to fail faster.. If you plan to use solid couplers or delete the couplers you would benefit greatly by doing what I have done to reduce or eliminate runout.
what are you defining as run ouf? Assuming your assembly is rebuilt right and your distance between the engine and trans are identical to the original measurement then the only reason the tube would move is if the torque tube bolt at the bell housing is allowing the shaft to move. What am I missing?
what are you defining as run ouf? Assuming your assembly is rebuilt right and your distance between the engine and trans are identical to the original measurement then the only reason the tube would move is if the torque tube bolt at the bell housing is allowing the shaft to move. What am I missing?
Runout can be Radial, Axial or Lateral, the pictures show how to check for all 3 on the individual parts.
Another point I've been meaning to bring up are the different noise when the TT is failing. When the O-ring loses grip on the bearing outside race you get the rattling growling sound as the bearing is flopping around in the housing bore. The clunking sound happens when the coupler has completely come apart, this noise happens mostly when you turn the engine off, the engine rotation stops fast but the drive shaft still has momentum and you hear the clunk when the coupler bolts hit the side of the flange. There is kind of a fail-safe mode that keeps the driveshaft from completely departing the input and output shafts, looking at the pictures you can see the output shaft stub that fits into a socket on the driveshaft, the input shaft is similar. Look at the picture showing the shinny area of the bolt head, this was made by the bolt head slapping back and forward against the tri-lobe flange after complete failure of the coupler. So that might give a little comfort knowing this when you are a few hundred miles from home. Or it's race day and right after morning practice it clunks when you turn off the engine and you have the points lead and the last race of the season starts in two hours. What would you do? Knowing what I know now I would roll the dice and go for it.
what are you defining as run ouf? Assuming your assembly is rebuilt right and your distance between the engine and trans are identical to the original measurement then the only reason the tube would move is if the torque tube bolt at the bell housing is allowing the shaft to move. What am I missing?
all valid points. i contend the runout that some are having is a direct results of the failure not the OEM part when it was installed. Good lesson is that your work demonstrates NOT to assume all one needs to do is replace bearings and seals.
i got a bearing set sent to me by a service shop team who do Vettes everyday. I was surprised when I checked the bearing model spec only to find the bearings are not stabilized in temp above 120 degrees . The tube as you know can reach the mid 2oo's. obviously the bearings are going back but it does throw up a caution flag on several fronts.
what bearings and seals did you actually end up with.? how did it work out?
it doesn't seem like you used the anti-creep bearing with the rubber seals in the outer race.
I'm about to lower the rear assembly but will need to get the right parts to do the right job.
i'm already aiming at adding a heat shield from DEI on the tunnel cover to help reduce heat from the exhaust
all valid points. i contend the runout that some are having is a direct results of the failure not the OEM part when it was installed. Good lesson is that your work demonstrates NOT to assume all one needs to do is replace bearings and seals.
i got a bearing set sent to me by a service shop team who do Vettes everyday. I was surprised when I checked the bearing model spec only to find the bearings are not stabilized in temp above 120 degrees . The tube as you know can reach the mid 2oo's. obviously the bearings are going back but it does throw up a caution flag on several fronts.
what bearings and seals did you actually end up with.? how did it work out?
it doesn't seem like you used the anti-creep bearing with the rubber seals in the outer race.
I'm about to lower the rear assembly but will need to get the right parts to do the right job.
i'm already aiming at adding a heat shield from DEI on the tunnel cover to help reduce heat from the exhaust
The TT failures are a directly related to the OEM parts with the amount of runout I measured, sloppy tolerances and incorrect materials the TT is challenged from day one. The original o-rings are Buna-N with a temperature rating of 250 F, I'm using Viton o-rings with a temperature rating of 450 F. Standard bearings have a temperature rating of 250 F , I think you were looking at the 120 C. The important point on the bearings is using the non-contact seal bearings because the bearing drag caused by the seals is about 3 times higher than the non-contact seals and the bearing outer race relies on the grip of the o-ring to keep it from spinning in the housing bore. I tried to find the anti-creep bearings with non-contact seals but they are not available. See pictures for bearing and o-ring part numbers, Amazon has them. Make sure to order the bearings with the correct suffix. You really should have your driveshaft, input and output shafts checked for excessive runout, if you don't you are rolling the dice. I'm going with a coupler delete 3.5" driveshaft because of the runout that I measured. Send me a PM if you want to have a phone conversation.
Last edited by Lemans Blue; Dec 13, 2024 at 09:17 PM.
The TT failures are a directly related to the OEM parts with the amount of runout I measured, sloppy tolerances and incorrect materials the TT is challenged from day one. The original o-rings are Buna-N with a temperature rating of 250 F, I'm using Viton o-rings with a temperature rating of 450 F. Standard bearings have a temperature rating of 250 F , I think you were looking at the 120 C. The important point on the bearings is using the non-contact seal bearings because the bearing drag caused by the seals is about 3 times higher than the non-contact seals and the bearing outer race relies on the grip of the o-ring to keep it from spinning in the housing bore. I tried to find the anti-creep bearings with non-contact seals but they are not available. See pictures for bearing and o-ring part numbers, Amazon has them. Make sure to order the bearings with the correct suffix. You really should have your driveshaft, input and output shafts checked for excessive runout, if you don't you are rolling the dice. I'm going with a coupler delete 3.5" driveshaft because of the runout that I measured. Send me a PM if you want to have a phone conversation.
i continue to put it all together. I fid checked further with mfr who didnt id C vs F. Turns out it was 120C.
now your comments are well received and have a lot of good info. Haven't remove the tube just yet but it’s close. Getting it checked by someone what their doing as well as the time to it may be the real challenge. I’m getting close to finding out what I’m up against.
thanks again for your diligence.
i continue to put it all together. I fid checked further with mfr who didnt id C vs F. Turns out it was 120C.
now your comments are well received and have a lot of good info. Haven't remove the tube just yet but it’s close. Getting it checked by someone what their doing as well as the time to it may be the real challenge. I’m getting close to finding out what I’m up against.
thanks again for your diligence.
Tom
i was looking up the bearings and noticed the spec number
i was looking up the bearings and noticed the spec number
Bearing 6007LLBC3 also has a /em type. The cost is quite different with or without the / em classification like nine ten times.
your photo shows the 6oo7 does have the /em but the 6008 doesn’t. Was there some reason
i know the EM indicates electric motor.
Yeah the EM not needed but won't hurt anything , I did not notice the EM when ordering but thats what they sent. I have a standing offer open to check and machine input and output shafts to reduce runout for a very low cost, If you want to send them to me or if you know a competent machinist/hobbyist that can do it, but there are a few critical steps that need to be done for best results. The input shaft really needs the scrutinizing & accurizing, the output shafts so far has been ok but the splined tri-lobe flange needs to be checked, machined if needed and clocked for the least runout. When my new 3.5" coupler delete driveshaft comes in I'll do a complete scrutinization of it and post up the results.
I just checked Amazon the 6007LLB bearing is available for about $12.
Torque Tube questions
