I tow really heavy everyday for work. Most of my driving is done on interstates mainly I-10. I would like to have a great towing gear for 65-70 mph and hopefully gain mpg.

I currently have 3.73 with 6 auto. I currently get 8-9 mpg for pulling 20,000 pounds. Now at 65-70 mph i am lugging real bad at 16-1800 rpms. I drive more in 5 gear at 22-2400 rpms in minor hilly terrains.

Would you guys go 4.10?? What rpms you in at 65-70 mph and what your mpg with load??

Would you guys go 4.33?? What rpms you in at 65-70 mph and what your mpg with load??

Would you go with even lower gear at highways speeds??? nah

 

I have 4.10's with a 6 speed manual, and I think at 65-70 I am around 2100-2300, my truck is 9750 lbs and my excavator and trailer are 14,700. My mileage has been constant at 8.8 mpg loaded and never over 11 mpg empty.

 

According to Cummins, you want to be geared to run 2150-2250 at 65 and no less than 1900 rpm. This comes from the Powerspec. www.powerspec.cummins.com

 

Personally I would stay with the 3.73. The 6spd auto has double overdrives and only having to drop down to 5th to keep the engine in the sweet spot. Running in the mountains maybe a different story though.

MikeyB

 

To me it sounds like you're in the sweet spot of the torque curve with what you have now.