6l80 2nd to 1st hard downshift

Brian Maxwell · December 27, 2020

From what I'm reading, hard downshift from time to time is 'normal' but I just can't get used to it. I've driven about 1,500 miles on my 2018 Silverado and get it every now and again. Hard enough that it bothers me. First time I really felt it, I thought I hit / ran over something. Truck has 19k miles total.

Any way to minimize the behavior? I saw a relearn process but it looked like for a 8 speed transmission.

Edited December 27, 2020 by Brian Maxwell
More info

diyer2 · December 27, 2020

If it was me I would change the trans fluid to a full 100% synthetic like Amsoil or Redline.

Brian Maxwell · December 27, 2020

21 minutes ago, diyer2 said:

If it was me I would change the trans fluid to a full 100% synthetic like Amsoil or Redline.

This is on my list once warranty runs out in March. Worth a try since I like Amsoil lubricants anyhow. I'm driving it far more frequently now so I can work out any kinks that may get caught in warranty before I dive in.

Bob2C · December 27, 2020

From what I'm reading, hard downshift from time to time is 'normal' but I just can't get used to it. I've driven about 1,500 miles on my 2018 Silverado and get it every now and again. Hard enough that it bothers me. First time I really felt it, I thought I hit / ran over something. Truck has 19k miles total.

Any way to minimize the behavior? I saw a relearn process but it looked like for a 8 speed transmission.

If you get it tuned that can be taken care of. But obviously it voids the warranty. Had mine tuned at 18k miles. Best thing I did. Got rid of that crappy idle too. Raised it to 600

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CamGTP · December 28, 2020

There is an adaptive learning reset and fast learn for the 6L80e, you just need the correct scan tool to make it happen. Any good transmission shop could do that. No idea what they would charge.

Brian Maxwell · December 28, 2020

Does the learning never figure itself out?

Brian Maxwell · September 23

Following up just in case someone comes along. This behavior slowly worsened over time to the point where I dropped the truck off at a shop. First they drove it and couldn't replicate. I said it's usually only after extended trips.

They drove it again, replicated, and have diagnosed as issues with the torque converter slipping which creates excessive heat and requiring a rebuild. Stated the high temp causes the trans to go into some sort of a panic state.

Called another shop to corroborate the findings and get a competitive price and they seemed to think it's early for the issue to present but sounds about right.

I'm in for a billit torque converter and trans rebuild at 47,000 miles.

Edited September 23 by Brian Maxwell