Some good info here.
Some funny crap.
Some just plain BS.
You ain't gonna hurt anything downshifting a newer auto.
Just watch the tach and don't get crazy.
The nanies wont let you overspeed and drop a valve.
But if you try to go too low at higher speed, it ain't good for stuff.
As to real trucks, with electronic engines and retarders
Most meet or exceed pulling HP.
Meaning a 480hp engine is at 480hp braking or more.
The old rule about using one gear lower was with no retarder
And diesels have little hold back, due to no throttle plate and no pumping loss.
(IE. No vacuum)
But with a good retarder you can go down a hill as fast as you go up it in the same gear. And probably never touch the brake.
I always thought the one gear lower rule was stupid.
Think about it. It only applies if you turn around and go back down the hill you just climbed. One side might be different. You might be dropping into a canyon. Or, living here at the Allegheny plateau, you might have climbed it
miles ago. And the east is way worse than many think. I've run 48 personally.
Most of the big western passes are famous and well marked.
We routinely have western drivers have issues here. Our grades are not usually as long, but steeper and no fanfare. Complacency anywhere can kill.
