Hello all hope everyone is doing well. My 2017 C7 non Z51 (34,000k) automatic shifts into second gear rather abruptly . Since this only has happened the last few weeks I was wondering if anyone else has experienced this . Owners manual says no dipstick to check fluid . btw .. Happens much less when warm but still occasionally . Thanks all !

 

acfcrown....all well here on my end! You may wish to post the same in the C7 section of this forum as you have stumbled into the C8 forum. Or, perhaps the mods will note and get it there before you.

 

Oops , thanks !

 

Following

 

My '17 GS did that but only when it was cold out (say below 45) and only the first or second sift before it warmed up.
It stopped after I installed my Range device. Doesn't seem that the Range would have anything to do with it, but like I said, it's never shifted hard since.

 

The A8's are a learning transmission; for what ever reason, the early ones have issues with hard shifts into second along with "Garage Shift". I have 97K miles on mine and both issues come and go at will. Sounds like you are still within the drive train warranty if not the bumper to bumper fix-it time; I would take in to your dealer and ask for the latest trans fluid flush and or the latest re-flash of the shift module.

Good Luck,
MK

 

Just have the dealer clear the "shift adapts" and then do the garage relearn procedure , the trans will shift funky for a 100 or so miles as it relearns the pressure and rpms that it takes to make the perfect shift

Dave

 

fluid level might be wrong, correct way to do it is to get it to a certain temperature and check that temp by using the sensors in the car, not putting some dumb laser pointer type thermometer thing on the underside of the transmission (very inaccurate reading). then when up to proper temp, undo the drain bolt and let it drain until a very slow drip and youre done. 140deg F was right around the middle of the range. if you let it heat up by just idling, expect to let it sit at least 20min. do not brake torque the car, hell with that. waiting while it idles costs you nothing but patience and a few pinches of gas.

going to dealer and asking them to reset the clutch learns/transmission adapts is a pretty straightforward thing. do that first, then expect the car to drive slightly imperfect. theres also a 'fast' learn procedure which they do after a transmission swap. how do i know? just got my car home today from the shop. it actually drives pretty smooth.

bottom line, as times goes on it learns/adjusts a few things. theres a bulletin for it. correct way to do the learning the long way is to have it in manual mode and putz along at a certain rpm range in this gear, a certain rpm range in that gear, etc. the 1-2 shift is handled by clutch 4, there are 5 within the 8L90 transmission. do so more reading, then hit the dealer, and get on with it =D

 

Subscribed. This is the one thing that aggravates me about my 17 GS. For what it is worth, I also use the Range device and have seen no difference with this particular issue.

 

What is the benefit of the Range device (other than this issue) ?

 

That's a great idea , I didn't realize I was still under warranty ...

 

To keep active fuel management from being active. Keeps all 8 cylinders running, always.

 

A range device will NOT help hard Upshift or Downshift or hard engagement into drive or reverse

Thats what the CLEAR ADAPTs and GARAGE FAST LEARN procedure is for, it clears any of the adaptive shift values out of the TCM and then does an initial clutch pressure reset for all the clutches, then for the next 100 miles or so the TCM is monitoring the input shaft speed and the output shaft speed making adjustments to the timing and shift pressure as it looks for the optimal settings for each shift based on RPM . You can do it manually but it takes a lot longer and u risk getting a ticket as you have to make some rapid acceleration and deceleration runs based on what shift you are trying to fix

its just easier to have the dealer or transmisson shop do the procedure above as it takes about 10 minutes tops

I have the GDS2 and the MDI interface so I do my own
Dave

 

The problem, at least around here, is the dealership usually acts like anything that you ask them to do is completely foreign and something they have never heard of (I have experienced it with the Mag ride software update, cracked wheels, the trans triple flush shudder fix)....it gets to be exhausting to try to deal with them.

Is there any sites or documentation that you could direct me to for which GDS2 and the MDI to buy and the instructions for using them?

Thanks

 

I could but the knock off MDI device and software is a challenge to setup . But the bigger issue is if you dont know what you are doing you can mess things up as there are no instructions
so an example is to do the garage relearn the trans has to be at 180 degrees otherwise it will fail ... if you push the wrong button you could "brick" your car

If you are still up for it send me an email at Dcasole at comcast.net as its easier to explain in email

Dave

 

Have the same issue with my 2019. Dealership and GM said it was normal. GM seems to be the only car company that explains problems as being normal. Calling it normal I guess gets them from fixing the issue. Mine only has the issue one time when you first start it and its fine after.

Glad GM is not in the medical business.

 

The Fluid drain back has been a well document problem but did not think the later years had it . The fix was a new valve body

I let my 15 run for a few seconds before I put it in gear , letting the converter and valve body to fill and have never had the bang into gear others have reported

Dave

 

Don't think that's the same issue. The Fluid drain back TSB (16-NA-014) list the issue when changing from P to D or P to R. I'm having a very delayed shift from 1-2 when first started. Will only do it once and it's fine after.

Be Safe!

 

It's a good sign when shifting hard into 2nd.

 

Is it a hard shift everytime the car goes into 2nd? Does it only do it from 1st to 2nd or from 3rd to 2nd?

My Camaro with the A8 always did a hard 1-2 shift, first shift of the day. Using the paddles to manually go into 2nd avoided the issue.

​​​​​​its a transmission problem, if you haven't, I would recommend getting the most current A8 TSB flush done.