Downhill & Shifting Issues

Bales9er · Apr 2, 2026

So I just turned 60K miles and recently noticed that whenever I'm driving downhill it's acting as if its got an engine brake, slows down and RPMs rise where it used to just coast downhill. Also just general shifting through the first few gears the RPMs have gotten noticably higher than I ever remember before each shift occurs. Most recent oil change the dealer recommended fluid changes for crank case and transmission but I haven't done them yet. Anyone else experience these issues?

Chopper_Man · Apr 2, 2026

That's how an automatic transmission are supposed to work, the downshifting. Transmission should be done every 30k IMHO. Your "crank case" is just engine oil change. Perhaps you mean transfer case and/or differentials?

Bales9er · Apr 2, 2026

Yeah sorry i meant transfer case...and as far as the shifting goes, it's more that it popped up as a noticeable difference from what I've been used to with this truck since ive had it. There was never any slowing down on downhills before, its almost like the tow/haul is on but it's not...

CDNSS · Apr 6, 2026

Mine does that going down hill with cruise on it holds lower gear from going uphill when you go down I have to click cruise off to get it to upshift. Very annoying

Also if you have tow haul on it holds it in lower gear too long IMO

Andystoy AT4 · Apr 6, 2026

My 2025 AT4 has adaptive cruise control and it tried to slow the truck going downhill so I turned it off along with lane control and the slippery road help switch and it now drives like I want it to. Too many GM nanny "here let me drive functions" for me. It will also do that with the tow/haul on as already mentioned.