Help with A8 shifting problem

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Oct 30, 2016 | 04:41 PM

RArvin

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Help with A8 shifting problem

Seeking help in diagnosing a problem with my A8 tranny. It is only noticed on highways where the engine is at or near 1500 rpms. The tach will then fluctuate 300 rpms above and below the 1500 with no noticeable change in speed. Often, it will happen quickly enough to create a drivetrain vibration that felt as if I were riding over stones. This happens in ECO, TOUR and SPORT modes and the engine is not changing from V4 to V8 or vice versa. My common sense opinion not owing to extensive mechanical knowledge is that the tranny is shifting back and forth between 2 gears quickly enough to cause this vibration. In manual mode at gear 8 while also at 1500 rpms no problem is noticed.
This was mentioned to the Corvette specialist at my local dealer before I had the chance to fully observe this condition. His answer was that it was the AFM. Any advice from you guys as to this condition would be greatly appreciated possibly having experienced this or whether it may be mechanical or computer generated. Any insight gained will help me in explaining this problem to the Service Dept. specialist so that I will not be viewed as a complete idiot. Mine is a 2015 Stingray with 6,900 miles.
All the best to you all and thanks again,
Ralph

Oct 30, 2016 | 04:46 PM

lakemg

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Sounds like you need a new torque converter...been an issue for many folks...

On edit: Search the site a little more and you'll find issue on the latest TSB (technical service bulletin) indicating how to test for the torque converter issue.

Last edited by lakemg; Oct 30, 2016 at 04:47 PM.

Oct 30, 2016 | 04:58 PM

Rebel Yell

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From: Down south in Dixie

I have felt this on a few occasions when starting up an incline in the road while cruising at higher interstate speeds. I did noticed the car was going back into the V8 mode a couple of times, and I chalked it up to that. It doesn't do it while in town, or in the suburbs at lower speeds. Please keep us updated if there is a problem. I do hope your baby is OK. Good luck.

I was certainly hoping it wasn't the TC as lakemg stated.

Last edited by Rebel Yell; Oct 30, 2016 at 04:59 PM.

Oct 30, 2016 | 05:01 PM

RArvin

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Thank you. Will certainly take your advice. Be well.
Ralph

Oct 30, 2016 | 05:50 PM

Red C8 of Jax

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From: Jacksonville FL

Quote:

Originally Posted by lakemg

I agree, sounds like your TC. I had my TC replaced 12K miles ago and the car has been flawless.

Nov 3, 2016 | 02:53 PM

RArvin

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Pertaining to my post on 10/13/2016 describing the problem with vibration in my 2015 Stingray's drive train, the Corvette specialist informed me today that GM has instructed him to pull the Transmission and TC. I assumed that this was for replacement of either or both. I will inquire further while securing a loaner later this week. My question is if these units are not going to be replaced, what would be some of the procedures used to effect repairs in the week they intend to have it in their shop? Not being thrilled at the idea of tearing apart the entire rear end in order to accomplish this repair, I can appreciate their quick decision with no stalling or delay. The mileage of 6,600 may have been a factor or not. Thanks for any input. As always, be well.
Ralph

Nov 3, 2016 | 03:02 PM

lakemg

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Hi Ralph, to answer your question. They will replace the torque converter rather than repair it. My guess is that they will install a brand new torque converter. The transmission has to be removed in order to access the torque converter. They will install the new torque converter, re-install the same transmission and button everything back up to normal. So in summary, new torque converter + original transmission will get you back up and running. Keep us posted on how things go.

Nov 3, 2016 | 03:15 PM

AllVelocity

Cruising

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Also tell them you have delayed shift issues, This will get you the stator shaft support replacement TSB. If they have the trans out you might as well get that done too.