Automatic transmission with Jake's going down the hill

MACK E-6 · Dec 22, 2025 at 7:46 PM

mitmaks said: ↑

So which rpm is normal for 12 speed auto with 3.08 gears? I thought anything over 1500 is a no no
Click to expand...

They redline a lot higher than that.

1300 to 1500 is good for cruising. At least that way you won’t be downshifting at the first sight of a hill.

Engine braking down a hill you’ll be good up to 2000 or so.

Powder Joints · Dec 22, 2025 at 9:02 PM

2000 -2100 max engine braking rpm

rollin coal · Dec 22, 2025 at 11:51 PM

Powder Joints said: ↑

I dont consider using my brakes going down hill, riding my brakes. I use my brakes including the engine brake when I think its the best way to handle a situation. When I teach a new driver I dont even allow them the use of a engine brake for the first 4 weeks or so. They need to be taught how to control there speed without one.
I have never had a problem with my brakes overheating.
Most drivers are not paying attention and enter the downhill at to high of speed to start with,
Click to expand...

The new Detroits and DT12 transmission you don't need to use the service brakes at all going down most grades. Someone posted it was good for 8% grade holding back 80,000 lbs from what I've seen that's spot on. Really good jake's on these modern detroits with autos is an understatement...

Log in or Sign up

Forums

Find Trucking Jobs

Automatic transmission with Jake's going down the hill

MACK E-6 Moderator Staff Member

Trucking Jobs in 30 seconds

Wait, employers can't reach you!

Powder Joints Subjective Prognosticator

rollin coal Road Train Member

Trucking Jobs in 30 seconds

Wait, employers can't reach you!

Log in or Sign up

Useful Searches

Find Trucking Jobs

Automatic transmission with Jake's going down the hill

MACK E-6 Moderator Staff Member

Wait, employers can't reach you!

Powder Joints Subjective Prognosticator

rollin coal Road Train Member

Wait, employers can't reach you!