Buttersvette

Just bought a 2017 GS one month ago. I went on my first long trip about 500 miles round trip. I was on freeway 90% of time going 70-80 mph. As I am cruising along at about 75 the car would feel like it was going back and forth between gears. I watched the RPM’s and it would drop about 200-300 rpm’s than go back up. It did this for two hours of freeway driving. It kind of just jerked back and forth. I put on cruise control and it continue to skip back and forth. Really quite annoying and no way this could be how this car is suppose to cruise along. It feels like the tranny is searching for the right gear, but I increased my speed and the problem continued. I will say despite this annoyance this car is an absolute blast and so hard not to look down and see you are cruising at 90. The car has 25k. Any ideas on what this could be or is this normal?

Jason71

Sounds like V4 mode activation to me. Put it in sport mode and see if it continues.

gliot1

Sounds like are running in Eco mode to me. I tried it once and that was once too many. I have an M7 so it only runs there if I select it. I believe it is different on A8s and has to be disabled somehow.

Buttersvette

That is what I was thinking but it will let you know when it goes into v4 mode on the dash and those never correlated with each other at all. I also sped up to make sure v4 mode would never come on and it still did it. when cruise was on it just kept going back and forth every few seconds. Really strange.

Buttersvette

I was driving in tour mode the whole way. I didn’t even think of switching modes to see if the problem would go away. I will take a drive today and see if switching modes will help.

Buttersvette

Yea I wanted a manual but my wife wanted an auto... I guess if there is something wrong I can blame her. Lol

Maxpowers

^^^
Switching modes in the A8 won't deactivate AFM (V4 mode). Try switching to manual shifts (which disables AFM) via the padels and see if the symptoms continue.

speed4tu

Put it in sport or select the sport gauge cluster you you can see the tach move better. Drive along around 60-65 mph and allow V4 to activate. Then watch the tach to see if it is continually moving up and down at 3-400 RPM variance at all times. If so you have the shudder issue like almost every other A8 that GM installled in various vehicles. Dealer will do a fluid swap that will bandaid it for a while.

Buttersvette

Actually I did do that for a while and remember it did not do it as much at a higher rpm in 7th. But I am pretty sure when I went to 8 it continued. But I will try that also.

eboggs_jkvl

Put it in "M" That will block the V4 AFM from happening. If the shuddering stops, then you need a visit to the dealer for a triple flush. Ignoring it will end up with a convertor replacement.

If the shuddering stops, you can get a "Range" device and that will also stop the V4 from happening. It won't fix the issue but it will stop the issue. The only fix is the dealer.


Elmer

Buttersvette

I thought it might be the v4 and tried different speeds and it continued. I have heard the “shudder” problem from other posts but not sure this is the case. Shudder or vibrating to me seems like wheels out of balance, this was like the tranny was trying to pick 7 or 8 as the gear it should be in. It was like when you had a three speed Auto back in the day, going in the mountains and the car kept shifting back and forth...

I guess I could see how some might describe that as shudder.

Buttersvette

Still under factory warranty for a few months. I wasn’t sure if I should by extended warranty but think that is probably a good idea at this point.

Buttersvette

Our dealer is so bad. They will probably say “just part of the Corvette’s characteristics and how it drives”. That seemed to be there response with my CTS-V problems.

eboggs_jkvl

Get the issue on "RECORD". Once you have it on record, you can keep at them to repair it or another dealer can go at it and because it is on "RECORD", they might cover it under warranty. There is a TSB on this stuff and it is easy to confirm the problem with their equipment monitoring the car on a test drive.

Elmer

Buttersvette

When these trannies have problems do they ever give a fault code?

eboggs_jkvl

I don't recall any one mentioning a fault code popping up due to this issue.

Elmer

Buttersvette

I have learned when there is a problem video evidence helps. I filmed this on my phone. just need somebody smart enough to fix it.

eboggs_jkvl

The first fix was to replace the convertor. THey ran out of spare parts! LOL. They finally figured it was due to the fluid soaking in moisture and developed a new transmission fluid to correct the issue. Needs a triple flush to get all of the old fluid out of the system.

Vetteman Jack

If you do not trust your dealer to find out what the problem is and fix it right, then find another dealer. You might want to touch base with the members in the appropriate regional section who may have a recommended dealer to take it to. Best of luck with this.

eboggs_jkvl

Got to be one dealer in California that can diagnose and fix the problem.

Elmer