Low RPM's ?

[kswieringa]

I live by a lake in a resort area and have a mountainous 2 lane road to get there . Problem is I usually find myself in a parade of cars getting there. That puts me around 50-55 mph in OD @ 1400 rpm or less w/very light throttle . IS this OK 3. 54 gears 265/75-16's

Am going to 305/70-16's aka 33/12. 50's

 

[KatDiesel]

I lock out overdrive anything under 55mph in my 4. 10 truck.



Thats the easiest way to handle it and not worry bout it.

 

[Mactruck]

Kat's right!

I concur with Kat. You and I have Identical trucks (4x4 QC AT 3. 54's). And I have 295/75r16's (33. 5x11. 5) bfg tires. I lock out my O/D around 55 - 60 MPH. The range you should be in so your not lugging the engine is around 1800-2000 rpm. The Power range where you get your most torque is between 2000 - 2250 RPM (Give or take a few hundred)



You are not saving fuel by running the Cummins at a lower RPM. You'll get the same MPG at the 1800 - 2000 rpm mark if you do the math. And you wont be putting any unnecessary fuel into the motor. If you have an EGT gauge you would notice a reading at 55 mph in OD at around 800 - 900 degrees (depending on your modifications). At 55 with the OD off you would see EGT's around 500 with much better power response when you need it.

JMHO

 

[Tom C]

I was told to lock out of OD when below 50 MPH. this will help prolong the life of your AT. Bill K did not like it when I told him I was running in OD at 1000 RPM!!! He emphasized not to do that that it would hurt the transmission. so I lock out of OD at 50.



good luck

 

[kswieringa]

TY

Thanks guys, sounds like it's time for some gauges.

 

[Snow man]

Mine will not go down to 1000Rpm in oD,it will kick to drive automatically at 1250 RPM. With 4. 10's I wont let it go into OD until 50 or so,Id rather it rev than twist the transmission to shreds.