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My temps will jump up and down a bit during normal driving nothing significant .
Unless I am racing, I don't even look at my temps , last time I did I think it was around 150 F just driving normal when warmed up
Making some really hard 1/4 mile pulls it would climb to 170 to 190
This is with the stock converter
So it depends , if you are road racing racing or have a higher stall converter there could be the chance that you could over heat the trans fluid but if you are just driving normal and making a few zero to 100 MPH pulls the chance of overheating is slim
When I checked with my dealer they wanted $700.00 to replace the harness , That's why I chose to do it myself as I have the tools and a quick jack . It was not a hard job at all to do
Dave
so with the quick jack were you able to do this procedure ? Relatively without trouble ?
We now have have the same issue with our 2017 Z51 A8.
History:
Purchased new in 2017.
10-2018; 19,790 miles: Had a simple drain/refill of the trans/filter because other people were reporting problems. No problems before or after.
07-2019; 29,494 miles: Triple flush per GM bulletin.
05-2025; 61,738 miles: Transmission fluid & filter drain/refill. No problems before or after.
08-2025; ~63,000 miles: While driving steady 70 mph in Drive, I downshifted to 7 with paddle. Shift really slammed hard, tried a second time and same.
I stopped using paddles until we got to destination, return drive was normal in and has stayed normal after. Dealer Tech checked codes, none. He said best idea was to continue driving and see what happens. Operation continues to be normal.
04-2026: 66,506 miles: Oil change. Checked levels on trans & dif fluid, normal. DTC code P0711 showed (only), cleared and told to drive for a week and retest.
05-2026: 66,770 miles: Dealer checked codes, P0711 has returned but trans still seems normal. Tech says this is a common problem with the A8, he bought a used C7 last year and he quickly changed the harness preemptively to preclude the problem. He says he has seen many GM vehicles with this problem on the A8 and changing the harness has fixed the issue 100% of the time, the new part seems better and he's not seeing repeats on the same car. At no time have we had a CEL or other indication of problems, Tech says CEL will eventually show. First appointment with him is 5-27.
We now have have the same issue with our 2017 Z51 A8.
History:
Purchased new in 2017.
10-2018; 19,790 miles: Had a simple drain/refill of the trans/filter because other people were reporting problems. No problems before or after.
07-2019; 29,494 miles: Triple flush per GM bulletin.
05-2025; 61,738 miles: Transmission fluid & filter drain/refill. No problems before or after.
08-2025; ~63,000 miles: While driving steady 70 mph in Drive, I downshifted to 7 with paddle. Shift really slammed hard, tried a second time and same.
I stopped using paddles until we got to destination, return drive was normal in and has stayed normal after. Dealer Tech checked codes, none. He said best idea was to continue driving and see what happens. Operation continues to be normal.
04-2026: 66,506 miles: Oil change. Checked levels on trans & dif fluid, normal. DTC code P0711 showed (only), cleared and told to drive for a week and retest.
05-2026: 66,770 miles: Dealer checked codes, P0711 has returned but trans still seems normal. Tech says this is a common problem with the A8, he bought a used C7 last year and he quickly changed the harness preemptively to preclude the problem. He says he has seen many GM vehicles with this problem on the A8 and changing the harness has fixed the issue 100% of the time, the new part seems better and he's not seeing repeats on the same car. At no time have we had a CEL or other indication of problems, Tech says CEL will eventually show. First appointment with him is 5-27.
Comments?
Just look at my orginal post #1 ... you will see my problem matches exactly what your tech said , I only replaced lower harness and its been fine for many miles ....
Dave
Just look at my orginal post #1 ... you will see my problem matches exactly what your tech said , I only replaced lower harness and its been fine for many miles ....
Dave
I agree, and your posts are excellent.
I was interested in seeing if the slam downshifts in 08-25 might be related to the temperature sensor. Your thoughts?
And I forgot to say that my tranny temps seems almost stuck at 100'. Never goes below that even when parked overnight, never goes above 125' while driving.
I agree, and your posts are excellent.
I was interested in seeing if the slam downshifts in 08-25 might be related to the temperature sensor. Your thoughts?
And I forgot to say that my tranny temps seems almost stuck at 100'. Never goes below that even when parked overnight, never goes above 125' while driving.
Jim , hard , delayed or just plain old sloppy shifts are signs that you need the "Garage Relearn Procedure" the dealer can do it for you , I have made a few posts about it , here is one https://www.corvetteforum.com/forums...ard-shift.html
This behavior is caused an "Adaptive TCM" that is used on the A6 and A8 transmission along with driving style , Heck I have even had to do the procedure on my car .. , once done you will need to vary your driving speeds for about 100 miles as the trans will be in learning mode as it seeks the best rpm and shift timing that it needs to make a perfect upshits and down shift , you might experence some crazy shifts at this time , it is completely normal
The bad harness has nothing to do with the shifts , the harness has a short in the lower section that affectsthe temperature "thermister"only , GM recommends replacing the upper along with the lower ... I have helped many people replace the harness and I have never seen an instance of needed to replace the upper harness
Feel free to PM or email me if you would like more detail
Dave
First I want to thank the OP. I love threads that actually fix something and are documented well enough to help others in the future. I try to do that when I discover a good fix. I had to do this repair on my 2015 vette recently. Totally fixed the problem. Not a hard repair. I wanted to contribute to the thread and pay it forward. Also note that my code reader is a cheap Innova 3100 code scanner that would not clear the code. Since the P0711 is a permanent code you need to have a good scanner or software that can clear permanent codes, or just wait for it to clear on its own after several key/warm up cycles. My code cleared by itself about 5 cycles.
As GM usually does there are updated part numbers for the harness and the filter. I have noted the changes below in case someone is needing to order this stuff for their fix. As noted above my car is a 2015 C7 and the parts below fixed me up, but I bet they are common for other vehicles also. But double check and do your homework.
New part number for A8 filter that fit my 2015 New part number for the A8 harness with temp sensor. Has the same colored wires as noted in the OP’s original post.
Tbis part number should work on a 2016 Z A8 correct ? I still feel GM should be doing the triple flush and harness for free if under 100k miles as much as tbis dang car cost me . And now they want me to drop another $150,000 on a new C8Z I'm not having g an easy time talking myself into buying it honestly I feel burned from my C7Z the rims cracking heat exchanger quit working heat soaked limp mode and now the transmission. Needs to be flushed 3 tines and a harness to fix a problem they developed should be free and this is why as much as it pains me I may never buy a corvette again because of all the crap I've had to Pony up money to fix on my C7Z.this posting had been. Very helpful thanks to all who have contributed. Be safe out there
^^^^^ You may feel that GM should pay for the triple flush, but they don't. Unfortunately, that's what counts.
I don't feel that we should have a "forever" warranty, but we should have cars that don't develop as many problems as GM.
40+ years ago we ditched GM for Toyota with our family cars, and never looked back. We have had 3 Toyotas that, by the time they reached 100k miles, required fewer repairs than any of our Corvettes in the first year. And the Corvette repairs are not related to the high performance nature of the car. The current problem with our 2017 transmission happens with all GM trannys of that type.
The reason we keep buying Corvettes is because it's such a great car to drive. I'd be happy to pay an extra $5k in the initial purchase price to get a Corvette that stays together, because I'll end up paying that much in repairs (or extended warranties) over our ownership time, plus the hassle.
About a year ago I mentioned to the Corvette Tech at our dealer that his section of the shop always has a couple of C8's with their guts all over the floor, and asked when he thought the C8 would become a reliable car. He thought about that for a minute and said "never".
