\Boost Monkey/

Just dropped my C7 off at dealer for delayed first of day park to drive (2 second delay then massive clunk and lurch after car sits for days). No other TC related symptoms like cruise rpm fluctuations or surging, but trans does act up on 1-2 and 2-1 in traffic...too much hunting. Only a couple grand miles on the car.

I had the 8L90 TSB in hand "#16-NA-014 - Delayed engagement after sitting overnight" and my SA says they have done one that he knows of (stator on a Z06) but I'm a little nervous due to how involved this TSB is.

Anybody been in my boat?

bbcb

curious what year and date is your car

\Boost Monkey/

2015 delivered June 4th, 2015 (end model year). So prior to TC revision and stator shaft TSB.

bbcb

good luck my 2016 was built two months later ...so I assume mine will someday have the same problems ....something to look forward to ...can hardly wait ...

jrizzuto

Just had mine done. Search for my post from a few days ago. So far so good, time will tell.
https://www.corvetteforum.com/forums...a8-repair.html

\Boost Monkey/

Nice... Good to hear.

So it got rid of the delayed engagement across the board? How does the transmission feel otherwise after the work?

I'm in Houston and my dealer is big... More work they have done and more Vettes have passed through the shop the better. I asked the 60 questions beforehand about their trans tech, Vette techs, etc.

chefcg1

Knock on wood for me as my build was 6/5/2015, I've had no issues with 8k on the clock. I have an A&A siting in the garage waiting to install if I ever get my autocal from Chuck "cow" that I have been patiently waiting on since APRIL. BUt honestly have been nervous to do the install with all the A8 issues members have posted.

iclick

How often would this occur? Every time after sitting for a certain number of days? Was there any difference in frequency in summer or winter?

FiveStar

Yes and yes its an improvement. Make sure the dealer reflashes the tcm because without a reflash it still wont be right. This is a reflash not just a relearn. What you will notice is the shifts are s bit slower less notchy and not as close together and down shifting comes earlier its a bit more Cadillac creamy and a bit less sporty feeling. I still have a clunk from time to time when coming to a stop after parking lot type of driving but its much more muted and less violent

FiveStar

Delayed engagement is gone yes. The garage shift is still a bit more clunky than I think it should be but not to harsh. What you have to watch out for is they have to take the whole rear end of the car off, tail pipes, rear suspension body panels its quite a dismantle job getting that transmission out of the car. look look look for panel damage and fit and finish issues before you drive off from the Dealer.

hisvett

Mine is dated 4/15 and I also have the delay shift, hard thump once in a while (down shift 2-1). Today I experienced a new one; we have been out running Route 66 this week and going into Oatman from the east side (very tight, twisty and hilly road) the car started to speed up when I manually shifted down into 2nd.....a very uneasy feeling. I will be speaking to my service tech as soon as we return.

W88fixer

Mine is an A6 so no personal skin in the game.

Always interesting to see machines like these in some state of disassembly. A lot of work for a shop and qualified mechanic, probably lots of unique, rarely used maintenance fixtures.

Good luck to any whose transmissions are having issues. Don

\Boost Monkey/

After sitting over a day or two or week...every single time I drove it. I will say though, that it was never a problem before and only started the last 3 months or so. But I bought the car last summer and had no problems during hot or cold.


IMHO, there is zero relation to outside temperature.

Richard Ames

Had it done about two months ago. Still have a delay from Park or Reverse to Drive when cold. Repair Order GM Tech stated normal at this time with a possible later update. The engine does a better job of braking when slowing was the improvement I noted.

\Boost Monkey/

Do you have the delay AND clunk/lurch forward when going into D, or just a delay. Consistent when cold out or just every now and then.

Weird mine started during warmer part of year.

iclick

Mine will delay perhaps 2-3 seconds followed by an abrupt engagement on the first cold start, but it occurs only about once every three months. It's amazing but it's as if there's some sort of clock in the A8 that triggers it. Any other time and it engages as you would expect.

As of today I have yet one more update. I was traveling to my dealer this morning, which is 35 miles away, to have my third free oil change performed. While on the way there I witnessed the well-documented AFM (V4) shuddering that I hadn't felt since last February. As before, it lasted about 10-15 miles and then quit, not felt on the return trip at all. So much for any relation to outside temperature, as in Feb. it was 55° and today it was well on its way to 96°. As before, put it in "M" where it reverts to V8 mode and the shuddering disappears. There is a very small amount of tach oscillation in V4 mode, perhaps ±25 rpm, but it's barely perceptible. Four months ago it was more noticeable, more like ±50 rpm. Like the shuddering, put it in "M" and the oscillation disappears.

I had two hard downshifts while decelerating to a stop in the first month of ownership but none for the past 16 months. I always attributed that to adaptive learning, but apparently some owners' cars are slow learners, as for them it doesn't go away. I also had a rather sloppy 1>2 shift or flaring (minor) for the first cold shift every morning, but that was mostly fixed with a TCM software update and "fast-learn." Shifting in general improved after that, too.

Other than that I can't fault the A8, and IMO the issues I've described are more idiosyncrasies than real problems. The shuddering is what has me baffled, and when it happens it doesn't feel right. What could cylinder deactivation have anything to do with the operation of the tranny? A drivetrain shouldn't shudder, period, so that's something that I will monitor closely. Just an explanation of why it shudders with be helpful.

FWIW, my build date was 12/18/14.

Richard Ames

Engagement cold is abrupt all shifting OK but I start slow from driveway as speed limit 30 for about a mile and a 90 degree in under 600 yards.

FiveStar

Make sure they reflashed the transmission control module. That reflash is half the battle. This is not a re learn but a complete update of the transmission shifting software.

05XLRtoC7_San Diego

Hi Boost, sorry to hear you've been having problems. Our 2015 C7s were built the same week last year.
I haven't had any problems (currently @ 6k miles). A bit nervous though how long that will last.
Hope things are resolved for ya, bro

\Boost Monkey/

Thanks man

No worries, it seems you drive yours a lot more often than me which I feel like is a good thing for this trans. I'm also very hard on my car, so that doesn't help either I'm sure even though it supposed to take it.

I hope yours makes it trouble free.