2017 GMC Sierra Denali Transmission clunking

tdeat13 · January 30, 2020

I recently purchased my truck in July. Its a 2017 with 45,000 miles on it. I am having an issue with the transmission clunking. It happens when i am going slow, usually pulling out of a parking spot or in stop and go traffic. When i tap the gas just to get moving and then take my foot off the gas the RPM's rev up. Then it seems like they struggle to go back down. But when they do go back down there is a loud clunk and the truck will kick forward. It is very loud and frankly very embarrassing when pulling out of work. Been to dealership 3 times since i bought it and the last time a couple days ago they said it was normal and that's just how the transmission was built.

I know there is a lawsuit with GM right now for this very thing but didn't know if anyone was able to correct this problem. It seems as though they fixed the problem in the 2018 models with a 10 speed transmission but their solution should not be just to deal with it or buy another truck. It boggles my mind how GM can know about this problem and say they can't do anything about it.

m3n00b · January 30, 2020

You need to relearn the 3-1 shift. Let me dig up the fix. Busy at the moment.....

It's Tim · January 30, 2020

Slip yoke.

m3n00b · January 31, 2020

I recently purchased my truck in July. Its a 2017 with 45,000 miles on it. I am having an issue with the transmission clunking. It happens when i am going slow, usually pulling out of a parking spot or in stop and go traffic. When i tap the gas just to get moving and then take my foot off the gas the RPM's rev up. Then it seems like they struggle to go back down. But when they do go back down there is a loud clunk and the truck will kick forward. It is very loud and frankly very embarrassing when pulling out of work. Been to dealership 3 times since i bought it and the last time a couple days ago they said it was normal and that's just how the transmission was built.

I know there is a lawsuit with GM right now for this very thing but didn't know if anyone was able to correct this problem. It seems as though they fixed the problem in the 2018 models with a 10 speed transmission but their solution should not be just to deal with it or buy another truck. It boggles my mind how GM can know about this problem and say they can't do anything about it.

Try this. Solved it for me

http://gm.oemdtc.com/492/transmission-adaptive-functions-and-correcting-low-mileage-harsh-shifts-2015-cadillac-chevrolet-gmc
To Learn C1 (For 6-7 or 3-1 Shift)

Pressure & Volume 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 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

Towards the end of the 5 miles I could feel the trans hunting around between 5-6 when cruising around 44mph.

It's smooth as silk when coming to a stop now. Friggn computers.

L86 All Terrain · January 31, 2020

Based on you saying you rev the truck and the revs seem to hold themselves up there and then bang into gear when it idles itself down, to me it sounds like your torque converter is draining itself or something similar then slamming because the rpm of the input shaft does not match the rpm of the crankshaft. Take it into GM and suggest you think the torque converter is having problems.

tlaw91 · February 2, 2020

You said you took to dealership 3 times and they say it’s normal

It’s an 8 Speed so there’s a three step process I use with multiple different bulletins I don’t feel like digging up right now lol

Basically it’s this-
1. Transmission service fast learn and drive learn
-If that doesn’t work then
2. Valve Body replacement and drive learn
-If that doesn’t work, then you pull out OL reliable
3. It’s an 8 speed doing 8 speed things have a nice day lol

8 speed transmissions are virtually indestructible. They’ll shudder and shift like a teen girl learning stick, but I’ve never seen a more reliable transmission from GM. 6 speeds however....[emoji51]

Post the repair orders here I’ll tell you what actually happened and what I’d do next.

You’re welcome

-Friendly neighborhood GM tech

Sent from my iPhone using Tapatalk