Lowering RPM ?

Direct drive transmission instead of overdrive.

 

I say time for a different truck. This is not an OTR truck. Sounds something better for local stuff

 

That truck is geared exactly right for his load and the speed he runs. The only thing I see is his transmission torque rating is low, which makes me think he has either a 1350 ft lb engine, or 1450. If he has a 1450 ft lb in his single axle, he is fine, the 1350 may be a little small, but will work great also. Many companies spec tall rears and direct drive transmissions to slow down the drive line, saving friction drag. These setups usually can't take great amounts of torque, but is perfect for the setup this guy has.

 

We did an rear end ratio change this year.
Big jump: we went from 3.55 to 4.11 because we were running some serious grades. At 3.55 the axles were running too hot the differentials were tearing themselves apart. (Had some busted hub seals give us the big warning it was time to change).

NOW, I've got the same problem. RPM's are too high at 62mph with 11R22.5
we are running about 1600 like you.

Our fix is getting 11R24.5 asap. I can't find anything so far that will let me calculate the RPM difference for this change. It's a popular question.

Yes, bigger tires will lower the RPM, by how much, I do not know.

 

Check out the cummins powerspec program. It let's you select you drive line and cruise speed for the top hole. Gives you the rpm's you'll run at.

 

You will lose some grade climbing power with the switch to taller rubber....just to let you know. There is no free lunch.

The Roadranger site will allow you to calculate road speed, rpm's, etc. with any rpm/trans/rear gear combo.

 

http://www.roadranger.com/ecm/groups/public/@pub/@eaton/@roadranger/documents/content/ct_062746.swf

Try here.

 

Yea. What he said....Maybe i missed something but a direct drive trans turnin 3.07'z???He should be runnin????No...actually that's about right. My bad. Sorry I blew up