Rpms

Uphill aim for whatever rpms will run the fan fast enough to cool it. Downhill rated rpms on the Jake

 

it depends on the motor and gearing.

 

ISX / 10 speed / 3.58's

Usually 1500, maybe 1600 up.

If your in the correct gear climbing, you should be able to accelerate. If you have the hammer mashed to the floor, and cannot gain any rpm's, then you need to drop it until you can.

 

And that basically sums up all you need to know.

 

Between 1350 - 1600 is sweet spot for engine. Going up I say stay around 1400-1600rpm. Going down it depends how good your jakes brake and your Gross Weight so 1500-1700rpm is max I would say going down.

 

My Cascadia with the DD15/DT12 combo will keep the engine around 2200 RPM on a steep downhill grade with a heavy load.
If the cruise control can't hold it at a steady speed I cancel the cruise with full engine brake, and add a little service brake as needed. If I keep it at or under 2200 there is no high RPM warning.

But that engine was designed to operate at that speed under those conditions. 2200 RPM while under power will damage it.

 

Used to be a time when 1700 would blow up the engine.

Specially if you kicked the jakes on.

Us old timers very seldom see 1800.

Must be why we're called super truckers.

 

i kept my truck in the high rpms. going down the mt for a little too long the other day. started to smell something weird and new.