CorvetteCali

This is going to sound very vague but I've been experiencing the 1-2 rough shift for a bit now off a cold start in my 8 Speed Auto 2016. Been in the shop for a week today and they "can't duplicate" the issue. Maybe my recent oil change the other day fixed it but I highly doubt it. Trying to get a TCM update but they seem to need to "diagnose the problem" first...Is that normal?

I should get the car back in the next day or two as they probably won't be able to duplicate it and probably have no idea what they are doing.

So my question is: Does this rough shifting for the first couple shifts off a cold start harm the car? And will this get worse for other gears or mean a bigger problem down the road? (All other shifting is fine after first few rough shifts)

Also I believe my car has had the feeling of "driving over rumble strips" on a smooth highway service a few times before, but hasn't happened in a while.

Thoughts from anyone who have had these problems and what to do next?

Thank you very much!

dash7510

I have the same 1-2 harsh shift on the 1st and/or 2nd shift when the transmission is cold. If you search the forum, you will see others have that issue too. I can't remember exactly who said it, but someone stated to manually shift it from 1st to 2nd a couple of times before setting off for the day. What I do is this. I back out of my garage, put it in manual, shift it from 1st to 2nd a couple times, shift it to drive, and drive off. After I do this, I don't have the harsh shifts. If the transmission gets cold, I repeat this procedure. I don't think the harsh shift hurts the transmission, but I don't like it so I do this work around. Hope this helps.

Dave

WelderGuy

How many miles on the car? How much time does it spend in V4 mode?

CorvetteCali

Don't like the feeling myself. Great idea, thanks!

But also does the issue get worse or mean bigger problems later? Any idea?

Appreciate it!

CorvetteCali

8900-9000

I would say quite a lot due to the fact I mainly drive on the freeways or 50-60mph mostly.

orca1946

Will a Range device improve this problem?

NSC5

All you need to do is shift from 1 to 2 manually once while the car is still stationary after you initially start it. The A8 is a clutch to clutch architecture transmission and ratios are selected by engaging and releasing specific clutch packs. The initial hydraulic fill is slow for a pack needed to engage second so the initial shift may be harsh as the pack partially engages resulting in momentary slight slippage which causes the transmission controller to immediately increase the apply pressure so that first shift to second is a slight slip followed by harsh engagement IF you do not do the 1 to 2 shift while stationary.

I have no idea why GM hasn't updated the software to do a slight pre-fill of this actuator control because after the initial fill each driving session there is no further issue with it. I do a 1 to 2 to 1 shift while my Z06 is stationary during the first start of the day and after that the shift with the car in motion is always smooth.

The Range is very beneficial to the transmission because it prevents V4 mode with the resulting modulation of the converter clutch which causes rapid wear. But the Range does nothing for this initial hydraulic priming issue.

Squeaky Wheel

FWIW, I’m not sure if this particular problem is just unique to the C7 A8. I recall a similar experience on occasion with my C6 with the A6. And always just with that first shift of the day. I just shrugged it off. Never had any other issues with it.

FunDriver

I've done both manual shift at first and also right into auto and don't recall much difference.

But I'm curious about your statement concerning rapid additional wear when in V4 mode. How much wear is this? And would this additional wear be covered by warranty? For instance clutch wear in a manual transmission is not covered. It seems that if this is substantial that there would be a lot of complaints and GM would do something about it.

NSC5

The complaints are certainly out there which is the RPM variation and shudder at steady cruising speed with the engine running in V4 mode and the lockup clutch no longer engaging as consistently as it should (and did when new). During V4 mode the lockup clutch is rapidly modulated on and off to help absorb V4 mode vibration and the amount of wear that occurs in a few hundred miles in this mode is more than you would normally see in a very well used transmission.

It is covered under warranty (see all of the replacement torque converters, triple fluid flush, new fluid type, etc.). The problem is worse with the LT1 because it goes into V4 mode quite frequently under cruising conditions while the problem is seldom seen with the LT4 equipped Z06 which goes into V4 mode only under very limited conditions.

The same problem shows up in other GM platforms using this transmission and AFM system and it seems worse with the 8L90 transmission probably because the torque converter was shrunk so that the 8L90 could fit within the same length/ space as the 6L80 6 speed.

rmorin1249

So am I to understand that when cruising on a level interstate at 70 mph in V4 mode, my torque converter is being damaged? If true, what idiot engineer at GM designed this POS?

Rebel Yell

I think everyone with the A8 has the strange/rough first shift of the morning. Fortunately I have a long driveway, and the car will go into 2nd about half way out. The shifts are good to go after that. Nature of the beast for the early C7's, and I don't know if the '17's - 19's do that deed. I just gotten used to it, and it doesn't bother me anymore. If the sucker falls out, the dealer can fix it. I've decided that I'm going to enjoy this car, and quit letting all the little quirks bother me.

Now, the "rumple strip" feeling is the torque converter going bad.

Internets_Ninja

Hard 1-2 shift when cold is normal. Supposedly the newer TCM flash can help mitigate it. The rumble strip is the converter. You need to have them do the triple trans fluid flush TSB on the car. If you still have a rumble after about 150-200 miles of having the flush done, they need to replace the torque converter.

dacbr131

Had a different issue w my 2016 Z51, with 6000 miles on it, A8 today. I was driving in Sport mode on the interstate for 10 minutes or so (everything should be warmed up by now) at the posted limit when a tractor trailer driver decided to squeeze me, causing me to depress the go pedal A LOT! The acceleration from 60 to nearly 80 was impressive and the tractor trailer was nicely disappearing in the rear view mirror! But when I let off the gas pedal due to traffic ahead the RPM's remained noticeably high (4K) for an uncomfortably long period of time. After 15 seconds or so the RPM's dropped to back cruising speed. Do I have an A8 problem???? What say ye?

rmorin1249

No problem. Tranny went into Performance Shift Mode. Normal.

SRQStingray

AORoads

It is covered under warranty for as long as there IS a warranty on the trans/powertrain. Unless I'm wrong, that's a weak part or design that will eventually bite some owner, be it the first or fourth owner.

NSC5

Which is why mine won't be going into V4 mode.

A special warranty extension showed up in the My Chevrolet owner center for my 2016 Z06 but it is for a fuel tank/pump issue and not the torque converter which GM should have issued a policy to cover given the high failure rate.

CorvetteCali

Yeah I read like 12 pages for like 2 hours, and had a few extra questions that I didn't see on there.

Thanks everyone! I think that helped answer my questions. Appreciate it!

arturobandini