The speed does not matter as long as it is constant. I placed the cruise control on at around 70 and watched my RPM's. They would move up and down a little. Your RPMs should hold steady while at constant speed unless your transmission is shifting from V4 to V8 to go up a hill.

Slow to go into gears. When I first got into my car and placed it into reverse to back out of the garage, the transmission would not shift and I would just sit for several seconds before the car would start in reverse. Also after the transmission warmed up and I stopped to do some shopping, maybe 2hrs, when I came out and started the car and placed it in reverse, it would jerk into gear. So I guess slow to go into gears and also jerking into gear.

 

Congratulations on getting your issue resolved!

Did the dealer list the part number for the new converter? Sometimes they don't but I thought I would ask anyway.

I can see the techs getting very good at doing this swap!

 

They did not show the part number on my paperwork. They have another C-7 2015 A8 coming in on Monday for torque converter failure. Practice makes perfect!!

 

Mine did that, cured last November with a new TCM software update and subsequent "fast-learn" procedure. Not sure when the update was released, but it was sometime last summer. What is the build date of your car? Only cars built after Sept. 29, 2014 can accept this update, I'm told.

 

- mid august

 

October, 2014

 

Do you think an aftermarket converter would help? We have a 2015 z06. Our first a8 failed at 13,000 miles in September. After that They put a new a8 in. When it got a couple thousand miles it started shifting into reverse and first hard again. We took it in and they reflashed it and said it was because our trans learned how to shift hard when it was learning itself. The reflash did help the problem but we parked it two days later so not sure how long that fix will last. We have since gone wild with mods....and the converter is on our list. I finally found out about the circle d one yesterday. https://www.corvetteforum.com/forums...-the-8l90.html

 

Maybe some members who had a successful reflash will post. If you have a bad torque converter, let the dealer install a new torque converter for you under warranty. It would help to go to a dealer who has diagnosed torque converter failures and their tech has replaced C-7 A8 transmissions or torque converters.

 

My Z51 Coupe is an early 2015 with the 8-speed. So far I have not noticed any issues with the transmission but it only has 4,000 miles on it. It is currently in hibernation mode in my heated garage and won't see daylight until April. I have not been back to the dealer yet to reflash the transmission or the PDR. In fact, it has never been back to the dealer. I have a lift and do my own oil changes. I replaced the oil filter only at 300 miles to lower the oil level and then replaced oil and filter at 500 miles as recommended.
I intend to take it on the highway in the Spring and turn on the cruise control to see if it surges at all. I don't usually use cruise control except on a long trip. If I do notice a problem I will try to get the dealer to replace the torque converter before the transmission is damaged. Maybe GM will issue a recall before then but I won't hold my breath for that to happen!

 

Yours is the first report I've read, from anyone who has replaced TC. Glad it worked out so well. I have all the symptoms, and have an appt. on Tues. with a local dealer. Just wondering if there has been any downside at all, like new rattles, leaks, misaligned body panel, etc. How long did the dealer have the car?

 

I had to find a dealer who had already diagnosed several torque converter failures and he had discussed the solution with GM. As I have mentioned, the first dealer I took my car to said nothing was wrong with my transmission. No downside, have not noticed any leaks, rattles and I did check the rear bumper closely because it has to come off to remove the tranny. The dealer kept my car 4 days; however, they decided to change my transmission filter and had to overnight it. I did ask the tech when he removed the tranny filter if he observed any metal filings in the pan and he said no filings were observed. So apparently the bad torque converter does not damage the transmission. Good luck with your dealer!

 

I'm nt saying our new ransmission has a bad converter....but it was replaced mid October so I bet it has the old version. That being said if we can reolace the tc now and not have another one blow we will. We have been looking for an aftermarket converter anyhow but not sure we want to invest anymore into a8 stuff. We were told by our dealer and GM that we voided our warranty driving it in a manner inconsistent with what it was meant for...and they weren't even going to warranty the first transmission failure....but they ended up paying for it out of a "goodwill gesture". We have snce added headers, e85, meth kit, tune, CAI, pulleys, catch can and NOS spray bars installed in the blower....you can bet nothing will be done "goodwill gesture" anymore. When the transmission blew we had 13,000 miles and it was completely stock. They said there was no fix for anything on the transmission and the only options were let them replace it or trade it in. lol We know that's BS but funny they have ego to think that....anyhow....I am not sure our tc failed....I had also read about one of the clutch housings developing a crack. Our symptoms were similar to that....but they are similar to this too. It had trouble shifting itself up when I had it in auto mode on the road course...then I parked it and we waited for hubby session and it wouldn't go. We had had it reflashed about 5000 miles.

 

I just returned from the dealer. They took my car for a test drive, and promptly ordered me a new TC and Transmission. Parts should arrive in a "few weeks".

 

Great news, let us know how you like the new TC & Tranny. Will make a BIG difference!!!!

 

Glad to hear all is well and no damage to the car.

Did you have the "HARSH 1-2 SHIFT" first drive of the day prior to repairs ??

tks

 

q
What year is your C7?

 

NO, I never had the "Harsh 1-2 Shift", I did have a jerk when I placed car in reverse. If you have only the Harsh 1-2 Shift you may not have a torque converter failure.

 

My 2015 Z51 A8 with ~16,000 miles was having the EXACT issues yours was with the vibration, literally exactly as how you described it. I took it in last week for an oil change and mentioned it and they diagnosed it as a bad torque converter. They had to order one but said it was safe to drive and wouldn't do any damage to the car in the meantime. I got the call yesterday that it had arrived so I'm dropping it off Thursday morning to be replaced. Supposedly they can do it in one day. I'm hoping my results are as good as yours were!

 

Glad I have decided on an M7 if I order a C7 Z.

 

I wouldn't be too glad, because as of October of last year every single 8L90 that leaves the plant comes equipped with the new TC that they are talking about in this thread.

So if you haven't bought a C7 yet, this is a non-issue for you.