I'm planning on picking up a Cummins to use for daily driving duties. 99% of the time it's going to be hauling me and my laptop to and from work. When I do tow my car - it will be around 6-7k lbs. I know I could tow this with a gasser - but I have always wanted a Cummins (you can call me a poser if you like )!!

With that being said - I've considered buying a turck with a 4.10 because I can get a great deal on it- then replacing the 4.10's with a 3.55 or so. I plan on running 33 or 35" tires so that needs to be figured into the equation.

I'm looking for fuel economy first and foremost.. any thoughts? With 600 ft/lbs I can't imagine that a 3.55 is going to make much of a difference. Worst case I guess I could just swap in a set of 3.73s and call it a day. But if I'm going to pay someone to swap ring/pinion I might as well put in a gear that makes the most sense for me.

Thanks in advance!
Jim

 

No 3.55 for the AAM. 3.41, 3.73, and 4.10. 3.41 would be great for light loads if the pcm can be programmed for that ratio. But if you can get a great deal on a truck with 4.10s, you'll still be getting some very good mileage even with them. The cost of changing them out would far outweigh any gains in mileage.
I tow more with my Hemi powered Ram than most tow with their Cummins powered Ram. It's a novelty worth having.

 

I got 4.10's w/auto on purpose because I tow 3000lbs. daily and 5500 occasionally.

I want to be able to run 33-35" tires and still have plenty of torque. Tire height alone should drop rpms to about =3.73 gearing.

Gears will run up to $3000 per axel then have to have the computer reflashed by the dealer.

Tires w/rims $1600 and have the computer reflashed.

I run mostly western Sierra foothills and my gasser was panting hard with 3.55's and 32" tires. My CTD does'nt even shift!

My mileage is 17-18 @ 70mph highway w/ 3000lb trailer and getting better daily. Only 3500 miles on my truck.