Cruising RPMs--how much is too much

[AHarris]

I noticed I turn around 2300 RPMs at 75 MPH--around 2450 at 80+. Does that hurt this engine over the long haul?



How much RPM over a long consistent period of time is too much for this big diesel?

 

[Bobcatpat]

I wouldn't think it would be a problem at all.

 

[jtwcummins]

You should be able to run the engine at red line for as long as you want without hurting it. Glad I got the auto trans, 80MPH is just over 2 grand

 

[johncameron]

I noticed I turn around 2300 RPMs at 75 MPH--around 2450 at 80+. Does that hurt this engine over the long haul?



How much RPM over a long consistent period of time is too much for this big diesel?

A stock Cummins engine was designed to operate anywhere between it's peak torque and redline all day long at 100% load!



Not a problem, it proabably is extremely happy at that rpm for sevral hundred thousand miles



John

 

[MJReynolds]

Okay this may be a dumb question but are you sure you've got 3. 73 gears? Your numbers look more like what I would expect with 4. 10s.

 

[Bigwhitehd]

no thats what i am turning with 3:73's and a g56. i will have 35's on it soon to combat the problem.

 

[2Rowdy]

Mine with the auto trans runs 2300 rpms @ 90 mph.

 

[AHarris]

Okay this may be a dumb question but are you sure you've got 3. 73 gears? Your numbers look more like what I would expect with 4. 10s.

I've got a G56 with 3. 73 gears

 

[klenger]

I don't think you can get a G56 with 4. 10s.

 

[AHarris]

I don't think you can get a G56 with 4. 10s.

You're correct. In fact the 2008s offer the G56 with either the regular 3. 73s or 3. 43s as an option. Now wouldn't that be nice!



If you want 4. 10s, you have to go with the 68RFE auto.

 

[MJReynolds]

I've got a G56 with 3. 73 gears

Sorry, it's just your rpm numbers seemed a bit higher than I would have expected given just the difference between the auto and manual trans. I guess I should look up the 6th gear ratios for the G56 and 68rfe.