Heavy Towing ??? - Diesel Forum

Blitzkrieg · 09-28-2007, 07:17 PM

When towing 7-10K pounds, is it a bad idea to use overdrive if only traveling 65 mph? I have the 4.10 rear and seeing 2100 rpm.

Thanks!

caryt · 09-28-2007, 08:57 PM

No problem..as long as the trans doesn't hunt your fine.

cary

SmokeyWren · 09-29-2007, 12:36 PM

The overdrive gear in your 4R100 tranny is not the weak sister that overdrive gears used to be. It's just another gear. So use it almost all the time. There are three conditions when you want to lock out overdrive:

1. Climbing a mountain pass, or any grade steep enough to cause a downshift out of OD.

2. Descending a mountain pass, to give you a tiny bit of engine braking while the "coast clutch" in the tranny does its thing.

3. In hilly country where the tranny is constantly shifting in and out of overdrive as you go up one hill and down another. Kill the OD until you get past those hills.

Your tranny is not going to "hunt". The programming in the PCM prevents hunting. Changing gears because of going up and down hills is not hunting - it's supposed to chose the right gear for the load. But frequent changing in and out of OD causes too much heat to go to the tranny coolers, and might overpower the coolers. So lock out OD in hill country.