Gear Ratio / Fuel Economy

[Makers]

Has anyone changed from 4. 10 gears to 3. 73 or 3. 55s, if so, how much fuel economy have you picked up? Also, how much have the RPM"s dropped?
Thanks
Mark

 

[JBee]

I had an 05 with 3. 73's and got around town 17mpg and at 60 mph was at 2000RPM. I now have an 06 with 4. 10's and get 15-16 mpg around town and run 2200RPM at 60mph.

 

[DerekW]

i went to the cummins website and it says the cummins like the rpms up a little for fuel economy. Also the main reason I feel for 4. 10's in the automatics was cuz dodge knew that it was the only way make the 48re and TCC live. they added more reduction to the rear ends to take the pressure off the automatics so they arent working so hard but just turning faster. Also if you are towing with the stock 48re my vote would be to leave it alone only cuz my experience swapping alot of gears.

 

[JBee]

I had an 05 with 3. 73's and got around town 17mpg and at 60 mph was at 2000RPM. I now have an 06 with 4. 10's and get 15-16 mpg around town and run 2200RPM at 60mph.

Oops I meant 70MPH, not 60, 1700RPM@60

 

[WaltHess]

I have an 01 dually 4x4, 6spd, with 4. 10's and I get between 18-21 mpg at 60. With the 235/85/16's the engine is running around 2,000 rpms. The speedo is a mirror of the tach in 6th gear. I was going to go with the 3. 55's until most guys noted how much better the 4. 10's did for towing.

 

[DGoyer]

I changed my 4. 10 to 3. 73 this winter. Worst part was getting the pinion bearing off. I dropped about 200 rpm at 60, still wanted less rpm put on 315's
rpm went down again now run 1900 at 70 getting 21 not loaded. Remember if you want to have fun and go past 2,000 a lot, mileage will drop to 16 fast.

03 6 sp 3500 quad 2wd lb