what is a safe RPM to run while running down the turnpike? right now at 70MPH my tach is reading about 2200 RPM`s .

 

2200 is not extreme, you can run those RPM's all day long and not hurt the motor.

I find that if I run 70 or over the only thing effected is the fuel economy

 

2200 is what I tow at, the motor seems to make the best power right in that range, when I get my gear Vendor's O/D installed, we will see how it goes at 1600

Tom

 

With 4.10 gears, 75 MPH = 2500 RPM. I've dragged a 5th wheel on the Interstates at 75 MPH for days (rush trip out West - 75 MPH speed limits), and the only thing hurt was my wallet (i.e., fuel consumption).

By the way, if your tires are as tall as you say and you have 3.54 gears, something's off. In my truck, 70 MPH = 2350 RPM with LT235/85R-16E tires. The same truck with 3.54 gears will turn 2000 RPM at 70 MPH. If you're really turning 2200 RPM at a true 70 MPH with tall tires, you may have 4.10 gears!!

Rusty

 

My truck with 315's and 3.54 gears turns 1800-1900 rpm's at 70. I've been known to turn 2500 rpm's for a while though.

 

These engines were made for medium duty trucks running "against the governor" all day long...22-2500 is nothing.

I only turn mine over 2100 for very short bursts...until the pyro's pegs (about 8 seconds from a 2100 pedal stomp )

Chris

 

my backhoe has a cummins motor in it, albeit a 4 cyl version, anyhow it has over 6500 hours and well over 2/3 of that time is at full throttle which is 3100rpm (after a lil' gov work) still goin great guns, still starts at 10* without no silly grid heater!

 

I only have 285's and at 70 my RPM's are 2000. You have 35's and you are turning higher RPM's? I'd say something is a miss.

 

I have 305's (33's) and my RPM's at 70 are right at 2000.