Harsh Shifting on the 8L90 Automatic Transmission

S-52L · February 13, 2017

I have a 2017 6.2 8 speed High Country that shifts exactly as you described. Completely unacceptable. It also has a bad hesitation/surge whether its shifting or in between shifts. Its not the AFM. I too cannot get the dealer or chevrolet to do anything. Its hard to believe there is not more publicity on this other than forum chatter. This is serious to me. If the dealer had disclosed the issue I never would have purchased this junk. Its also coincidental the dealers test drive route was limited and there was no fuel in the vehicle.

Cottonwoodguy · February 13, 2017

My truck need not even leave the parking lot to duplicate the shifting problem. The last update done did help the shifting some but the clunk on deceleration is absolutely horrible. It sounds like a u-joint with 500,000 miles on it. Also if I shift from reverse to nuetral it clunks quite loudly. I hate it.

AllTerrainX · February 13, 2017

TechLink article:

http://sandyblogs.com/techlink/?p=7170

There may be several harsh shifting conditions on some 2015-2016 Silverado, Sierra, Yukon and Escalade models equipped with the 5.3L engine (RPO L83) or 6.2L engine (RPO L86) and the 8L90 automatic transmission (RPOs M5U, M5X). The shift conditions may include:

Harsh 1-2 upshift (except for the first 1-2 upshift of the day)

Harsh 3-1 downshift when de-accelerating to a stop

Harsh downshift under heavy throttle apply

Active Fuel Management (AFM) V4 to V8 transition harshness (6.2L engine only)

Coast-down downshifts (6.2L engine only)

So with this information, is this something that should be brought up to the dealership to fix?

Dnt · February 14, 2017

Fixed with Hypertech 2.0 part 2000 with latest updates

Can you tell us what this entails? Is it a GM part or an aftermarket part? Did your dealer find this info or did you bring it to him?

Thanks

Hypertech 2.0 part 2000 is an aftermarket hand held tuner where you can choose settings for the Tire Size / AFM / Engine management /Trans shift points etc. to suit your wants and needs. Lots of discussion on thees threads about the aftermarket tuning voiding the factory warranty so use at your own risk. i just bought it for the ability to set AFM to only come on above a certain speed (currently set at 50mph) but I did experiment a with with some other settings (not going to admit publicly to having trans set so that it shifts like it should haha) and it does make driveability much better especially with the "SILLY" shifting 8 spd. too bad Gm did not give driver options for sport economy performance etc modes via a dashboard toggle switch or something, they would have eliminated a LOT of complaints.

15_silverado · February 15, 2017

Unfortunately the hypertech nor the Diablo Sport or any other hand held tuner is not available yet for the 2017 model year trucks.

But as soon as one becomes available I will get it without hesitation. The warranty is useless anyways as GM says everything is "normal"

S-52L · February 15, 2017

Maybe a GM tech on this forum will step up and tell the truth or gives us a hint at what might be in the works to fix this. A little "positive" would help instead of your on your own!

sk · February 15, 2017

Maybe a GM tech on this forum will step up and tell the truth or gives us a hint at what might be in the works to fix this. A little "positive" would help instead of your on your own!

The fix is listed in the first post ...

S-52L · February 15, 2017

The fix is listed in the first post ...

But I have a 2017 and it does not list the 2017?

m3n00b · February 16, 2017

Printed it off, gave it to my SA who said he couldn't find anything about it.

-tapa

m3n00b · October 17, 2018

Didn't mean to bump this thread...was trying to post in another...

This is how I fixed it.

https://gm.oemdtc.com/6777/16-na-019-information-on-transmission-adaptive-functions-and-correcting-low-mileage-harsh-shifts-slips-or-flares-2016-2017-buick-cadillac-chevrolet-gmc

To Learn C1 (For 6-7 or 3-1 Shift)

Pressure Learns:

Note: It is recommended to utilize a road with a speed limit between of 30-45 mph (48-72 km/h) for this procedure.

Shift the transmission into 6th gear with the PRNDM in the M position. Obtain an engine speed between 1000 and 1600 engine rpm. Maintain this condition for a total of about 5 miles (8 km). Cruise control may be used and has been found to result in faster learning of the clutch values.

Volume Learns:
- Complete 15 light throttle 6-7 upshifts at approximately 15% throttle to further learn C1.

I also did this:

To Learn C4 (For 1-2, 5-6, or 7-8 Shift)

Pressure Learns:

Note: It is recommended to utilize a road with a speed limit between of 40-45 mph (64-72 km/h) for this procedure.

Shift the transmission into 7th gear with the PRNDM in the M position. Obtain an engine speed between 1000 and 1750 rpm. Maintain this condition for a total of about 5 miles (8 km). Cruise control may be used and has been found to result in faster learning of the clutch values.

Important: Application Specific Express & Savana Vans Pressure Learns:Perform 10 normal mode 7-6 coast down shifts (zero/light brake) to learn the C4 Return Spring.

Volume Learns:
- Complete 15 light throttle 1-2 upshifts at approximately 15% throttle to further learn C4.

rkuhnjr · February 13, 2019

On 10/17/2018 at 9:40 AM, m3n00b said:

Didn't mean to bump this thread...was trying to post in another...

This is how I fixed it.

https://gm.oemdtc.com/6777/16-na-019-information-on-transmission-adaptive-functions-and-correcting-low-mileage-harsh-shifts-slips-or-flares-2016-2017-buick-cadillac-chevrolet-gmc

To Learn C1 (For 6-7 or 3-1 Shift)

Pressure Learns:

Did you need to do any resets in the computer before performing these steps? Or did you just take out to a quiet road and follow the steps and it worked? The hard shifting is driving me nuts but i dont have a GDS2 or any scanner for that matter, but if its just the steps listed then im going to try them out.

m3n00b · February 13, 2019

11 minutes ago, rkuhnjr said:

Did you need to do any resets in the computer before performing these steps? Or did you just take out to a quiet road and follow the steps and it worked? The hard shifting is driving me nuts but i dont have a GDS2 or any scanner for that matter, but if its just the steps listed then im going to try them out.

Just went out and did the drive. Didn't have to do anything else with the computer. I could feel the transmission start to learn all along the drive. It was a pretty cool experience.

rkuhnjr · February 13, 2019

Awesome, I figure i will try that first then before going through the dealer run around, see if it works for me as well

m3n00b · February 13, 2019

Awesome, I figure i will try that first then before going through the dealer run around, see if it works for me as well

Have fun. The trans started doing all sorts of weird shifts towards the end and finally leveled out and stopped kicking me in the ass when I came to a stop. Put on at least 10k miles since. Been perfect

rkuhnjr · February 13, 2019

When you did the Volume learns did you leave it M and manually shift or just put it in D and guess what gear you were in? mines a 2015 and doesnt tell me what gear its in unless im in manual