TRANSMISSION “JOLTS”

[pinebaron]

Talking of de-acceleration, I simply love the diesel exhaust brake, so uselful when drving down steep inclines and if there's a need to slow down, never owned anything that had an exhaust brake before, thought only big 18 wheelers had it. Takes a couple of moments to kick in but is awesome and between the exhaust brake and the 10-speed auto they work seamlessly together and can control the descent speed using the gas pedal (or something like that).

 

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[Chrisbert]

I'm guessing it's something they could address in software if they chose to.

 

[pinebaron]

I'm guessing it's something they could address in software if they chose to.

I had an ECU Software update in first week or two of ownership but that was linked to an emissions CEL issue but could also have been related to other issues, I dont know.

 

[SkyChimp]

I am now at 4000 miles and it pulses and jolts around 1100 to 1300 rpm at 40 mph. Hasn't cleared up and seems to be a flaw with either the Allison or the ECM. If the ECM is dynamic with a learning capability, it sure is slow to learn.

 

[fcodxdart]

I just got mine and I don't notice any jolts. I've been driving pretty carefully and I'm at 400 miles. Smooth as any truck I've ever had.

 

[J 2]

I've had a few hard shifts at 54, 55, 57mph. First 2 were close to each other on flat road feathering throttle due to close traffic. Last one was letting off throttle going slight down hill.

 

[DanTheRVMan]

UPDATE:

Dealership notified me there was an update shift map. Been about 2,000 miles after the updated shift map and NO ISSUES!!

Only issues I have now are:

• Trim pieces below the center display squeak in hot weather. Dealer is going to dismantle the trim pieces to find out what the issue is and fix.
• Passenger mirror occasionally won’t collapse.
• Mirrors won’t always collapse when truck is locked.

Great truck! A few small issues here and there.

 

[samuelrobinson3]

Just bought a Sierra 1500 5.3 L V8 w/ 22.000; noticed jolts at high speed on the interstate; then going uphill some; took it to the dealer and they said they see this a lot and it needs a new torque converter; hopefully that will fix it. Glad it's still under the drivetrain warranty.

 

[gemarsh]

Just bought a Sierra 1500 5.3 L V8 w/ 22.000; noticed jolts at high speed on the interstate; then going uphill some; took it to the dealer and they said they see this a lot and it needs a new torque converter; hopefully that will fix it. Glad it's still under the drivetrain warranty.

Welcome.

 

[pinebaron]

Welcome.

 

[jgaestel]

I have a 23 Sierra 2500 AT4 with similar issues. The dealer replaced the transmission as there are no valve bodies available for at least 4 months. After the transmission was replaced, I was still getting random low speed hard shifts. Took it back to the dealership. They reflashed the TCM and checked the transmission fluid. So far the hard shift have disappeared, except for the random low speed shift coming to a stop. We tow a small trailer in the mountains and my last two trips have had no issues. Maybe the transmission is learning. We shall see.

 

[samuelrobinson3]

I bought a 2021 Sierra SLT in December, 2024. I starting notice the truck "jolt" after it got warm/hot after driving for a while. I took it in and they replaced the Torque Converter (under warranty thank God) and it's been fine since. Fingers crossed but it's been a few weeks since I got it back and it's running smoothly now. This is a common problem w/ Sierras at any mileage - and GMC has lost a lot of money replacing parts/transmissions under the drivetrain warranty. I would tell them to check the torque converter and see if that helps. Good luck.

 

[NCB_’22AT4]

Have a 2022 at4 6.2l, 24k miles, going into the shop on Friday after experiencing a very hard jolt upon accelerating to pass. Yippee!

 

[Bpr3ece]

I have a 23 Sierra 2500 AT4 with similar issues. The dealer replaced the transmission as there are no valve bodies available for at least 4 months. After the transmission was replaced, I was still getting random low speed hard shifts. Took it back to the dealership. They reflashed the TCM and checked the transmission fluid. So far the hard shift have disappeared, except for the random low speed shift coming to a stop. We tow a small trailer in the mountains and my last two trips have had no issues. Maybe the transmission is learning. We shall see.

Im gonna go with the Next Gen Project Carbon Valve body. Im sure GM will void my trans warranty with a PPE deep trans pan. So ill just have to bite the bullet and do it myself.

 

[NCB_’22AT4]

Have a 2022 at4 6.2l, 24k miles, going into the shop on Friday after experiencing a very hard jolt upon accelerating to pass. Yippee!

Got back from dealership today. Couldn’t replicate said JOLT. Computer don’t find any codes or shimmers during road test. Time will tell.