I bought a 2006 with a 5.9 Cummins, 6 spd, 3.73, 11.5" rear new in 2007. Dealer was trying to get rid of it so I got a good deal. The problem is I have a camper top and don't tow heavy loads. I only use 2,4,6 gear. The truck is geared to go 55 and I want to drive 75. A gear vendors overdive would do the trick but is too pricey for the few miles I drive. I would need to go to a rear end ratio of 3. or less to accomplish this. No one that I know makes this. Since the truck has a spilt drive shaft already putting in a strait gear box and modifying the shaft would suit me fine. Know where I can get a 3. ring and pinion or straight gear box to do the job?

 

There's a 3.42 available now for the 11.5".

And then install taller tires like the Toyo Open Country AT in 285/75/17.

MikeyB