After 13 years of C5 M6 ownership, I went with the A8 in my C7. Long boring story why I caved to the “wave of the future”. I can say I definitely like the auto in this car compared to the A4 slush box I had in my first Corvette, a 1987 C4. I have a few concerns that keep me from loving this transmission that my research has failed to answer. Hoping other A8 owners can help me with their experience regarding my concerns and/or point me to some possible remedies. I am posting this in both the General and the Tech/Performance sections of the forum as I am not sure where I will get the best result. My car is a 2016 base (non-Z51) with mag ride bought off the dealer’s lot with an 09/15 date on the door sticker and now has about 3700 miles on it.

Issue one is the lag when paddle shifting 1-2 and to a lesser degree 2-3 at way less that WOT. Shifting at 3000 rpm the 1-2 shift will gain another 500 rpm before initiating and the 2-3 another 200-300 rpm. The rest of the upshifts are acceptably quick. I normally drive like grandma so I haven’t tested paddle shifting at WOT since I would likely be going much faster than I’m willing to exceed the posted speed limit before hitting third gear.

The second issue is on the downshift side, the shifts are quick and pretty much acceptable until the 3-2 shift, where the rev match makes the car feel like it is accelerating rather than providing any engine braking.

Third, on the first cold start of the day, I can put the transmission in reverse to leave the garage, let my foot off the brake, and the car just sits there for several seconds before starting to move. It’s like it has to build up some fluid pressure or something. I think I have seen a TSB issued (possibly for earlier model years) that required removal of the transmission to cure the problem.

Forth and finally, when cruising at a constant speed, the rpm’s will fluctuate 100-200 rpm with release and reapplication of throttle. Is this normal for a “locked up” A8? I came across a post somewhere that indicated the lockup had some slip built in to accommodate the AFM function.

I have no complaints about the automatic functioning of the transmission, it always seems to be in the right gear and shifts are positive but smooth. I bought my car from MacMulkin (about 700 miles from home), and the nearest big Corvette dealer is Criswell and over 180 miles away. The local dealers I have to choose from don’t sell (and probably service) many Corvettes so I would like to be able to offer some suggestions if and when I take it in for service. Thanks in advance for any help you can provide to point me toward some solutions that will make me love this transmission.

 

You are correct on a SB issued for the cold start delay, but to my knowledge it's only a re-flash and learn process that does NOT require the trans to be removed. Guys here on the forum seem to be about 50/50 on how well it works. I've been fortunate that my 2015 A8 has so far (13K) been problem free.
I do see the same thing on the up and down paddle shifts, BUT at WOT in sport or track it shifts fast and solid, so the part throttle lag upshift I can live with as when I'm doing that it's just to hear the sweet NPP sound.
My suggestion; do a couple WOT throttle upshifts (in a safe place of course) and see if your're not happier with the trans -- compared to my C6GS A6 it's much faster.
Also, on WOT upshifts it will POP pretty loud between gears. I understand it's a milli-second fuel shut off to shift quicker. First time I hear it I was concerned, now I LIKE IT!!!
Hope this helps - I'm not an expert as many are on here, so maybe someone can add to it and I'll also learn something too.

 

I never did any paddle shifting, so I can't help you with your paddle shifting problems. I have a 2015 A8 and also had the same symptoms you have with the first cold start, no movement of the tranny for several seconds and the fluctuating of the RPMs (100-200) at constant speed. I also noticed when my cruise control was on my tranny shuttered for several seconds, stopped, and after several seconds it would shuttered again. It would continue this shuddering as long as I had my cruise control on. I think you have the same torque converter as the one I had. My dealer said my torque converter had a bad o-ring and he replaced the torque converter with the new revised torque converter which I think was placed in all C-7 after October, 2015. After my new torque converter was installed, all of my tranny problems went away. I also thought my car was shifting very smoothly but after the new torque converter was installed it was super smooth. Don't know if the Torque converter is your problem, but I would suggest you take your car to a dealer who has already replaced some torque converts. The last count at my dealer, he had replaced 6 bad torque converters in C-7s.

 

My 2015 (build date 12/18/14) has had the slow-engagement issue when cold, but so far it only occurs once every three months and only in reverse. When it does this I've noticed the "R" on the display flashes until it engages, but it's never thrown a code. The last event was in Jan., so I'm a bit overdue for another one now. I did the software update plus fast relearn in Nov. and that didn't stop the delay in Jan., but did help greatly with overall shift behavior, including a bit of flaring I was having on the first 1-2 shift when cold.

I've witnessed very rare shuttering and usually present tach vacillation (only about 100 rpm total) in cruise control at highway speeds, but only in V4 mode. This has been seen in other cars but I can't wrap my head around how cylinder deactivation relates to tranny behavior. The shuttering hasn't recurred since Feb. and the tach vacillation continues but is much less noticeable lately, about 50 rpm total and sometimes none at all.

Tadge's recent comments on the A8 lead me to believe these glitches do not affect durability, and if this is true I can certainly live with the quirks rather than pulling the tranny for a fix for this very minor stuff. Otherwise, the A8 in my car has performed very well indeed.

 

What do I ask for if I take it in for service to get the software update and fast relearn? I too am reluctant to have the tranny pulled for the issues I am experiencing as it performs flawlessly (as far as I can tell) in auto where I usually drive it.

What do you mean by "flaring" and have you used paddle shifters before and/or after the update? If so, how much lag did/do you get on the 1-2 shift?

 

Tadge explained the delay between the paddle press and the shift a couple of months ago. Basically the PCM is calculating a bunch of things while preparing for the shift. Many people confused fast shifting (the actual mechanical gear shift within the transmission) with reaction time to the paddle.

 

I had mine done last Nov. and the software update was PI1473, but it can only be done on cars built on or after 09/29/2015. It's possible this has been updated since I had the job done, though, but if so I haven't seen it mentioned here. The "fast relearn" is performed in the service dept. unlike the old arcane method described in TSB #14-07-30-001A.

It's a sluggish upshift where revs increase more than they should between the shifts. Mine did it only for the first and perhaps second 1-2 shift on the first drive of the day. Most who complain about cold 1-2 shift problems reported hard shifts, however.

I almost never use the paddles, frankly. It shifts so efficiently in auto mode that I don't see the point for normal street driving. I'll be driving it tomorrow, weather permitting, and I'll do some checks on that.

 

Do a search and you will see that your symptoms with the rpm fluctuation is a sign that you need your torque converter replaced. Do a search and you will see other posts about this.

 

iclick, unfortunately your shuttering problem will slowly get worse until you will not have a pleasant driving experience while operating your car in cruise control. Your tach vacillation will be constant and your slow engagement will also occur on a regular basis when starting your car when it is cold. I hope this does not happen to you, but I have been there with the same transmission. Good luck.

 

Oddly, the shuddering is very rare. I noticed it driving back from the dealer when new and <50 miles on the clock back in Feb. 2015. I didn't notice it again until Feb. 4, 2016 for a short time, perhaps 10 miles, then it quit and hasn't resurfaced since.

The tach oscillation at cruise was first noticed on Feb. 4, 2016 showing about 100 rpm total. The next day I drove it and no shuddering with oscillation lower, about 50 rpm total. Since that time the oscillation is barely noticeable and today I drove it and noticed none at all. Both the oscillation and shuddering only occurred when in V4 mode.

I can say that it is shifting and behaving so well lately I would not want to touch anything. It only has 3800 miles on the clock, so perhaps I've got grief approaching in coming months or years. Tadge says mostA8s will not need service, so maybe I'll be one of the lucky ones.

 

I took a drive today and did some paddle shifting. I noticed very small delays from 1-2 and 2-3 during light to mild acceleration and shifting at around 3k RPM, so small that I would not have noticed had I not been concentrating on it. No flaring was noticed and shifts seemed quite normal. As mentioned before, I did the PI1473 software update and fast relearn last November.

 

built august 2015 ... very few miles on my car ...jerks when coming to stop ...first drive of day ..delay first to second gear....hope they have come up with an easy fix ....no way in hell is my car being torn apart ...
I hope ...

 

I notice my problems starting around 9K; however, prior to, I had not noticed any symptoms of a bad torque converter. Hopefully yours will not get any worse.

 

A8 Z51 A8 2015 build 12/14 9000 miles. Shift delay park to drive yes. Transmission reflash and transmission pulled for stater update. Fix for delay is a no as RO stated GM now considers normal . Some shift improvement and better engine braking is the net result. Would I do again, yes. Am I satisfied yes as it is something you now plan on.

 

"something you now plan on." how to you plan on and accept the fact that you tranny is going to out ..be rebuilt ...and hopfuly everything goes back together the way it should with no damage to the car ...paint ..rattles etc.... this is not my idea of new car experience ....forgive me ...but I have owned a lot of new cars ...never went through any of this crap !! or anything close to it ...

 

Non forum dealer so I cannot promote has a dedicated Corvette and trained mechanic and sponsers a club. Keeps a 58 in the showroom and not for sale. Did excellent work. Father in law was a Pontiac Buick GMC dealer and saw hundreds of transmissions pulled and rebuilt. The stater update is minor compared to a rebuild. The morning or "cold" delay is not something that will hurt the transmission in the long run. Just something you plan on.

 

June '15 build, base car, 4000 miles. Similar issues to the OP. Plan to ask Criswell service to evaluate and advise me when it goes in for first oil change in May. When I drive the car hard I love the way it performs but around town not so much. Driving 600+ miles to the Bash and hoping more miles won't hurt anything.

 

Bad T/C count on it.

 

You would no best Black&White!

 

Torque converter, it is an outright epidemic. No replacement insight for the near future. GM knew they were bad and just kept installing them anyway. Once they do get one for you, you will have a mechanic change it out that had training 9 months ago. Good luck getting everything aligned again. Can't wait to see my cobeled up scratched up $100k car when I get mine back. Hell, I hear about more damn corvette techs screwing up simple oil changes. I need to stop now.