Super hard shifts-08 Denali

[optimusprime]

2008 Yukon Xl Denali with 206k on the clock.

For as long as I can remember, I have had a super hard ”slamming” type shift from 2-3 and going around 20-25 mph. It happens around 85% of the time leaving the house when the truck isn’t very warm and randomly thereafter.

Along with that, I also get the same type of super slam shift when I floor it at higher speeds (merging traffic or trying to pass). Happens around 70% of the time in this situation.

Any thoughts as to what could be causing this?

 

[Marky Dissod]

When was the last time you changed your ATF & filter?
Hang on, let me try the batsignal ... @NickTransmissions ...
If it's been a while, when you go to change the ATF & filter, you'll likely be changing other things too.
With luck, Nick will tell you what needs changing.