I am the 2nd owner of a '90 D250 powered by the 5.9L Cummins with 153,000 miles. It has the Getrag manual 5spd transmission with a 4.10 gear and a traction lock differential. This truck is only a 2 wheel drive set up and runs like a top. I am currently able to get 25-29 mpg with this setup, but that's really taking it easy(I get an awful lot of fingers from impatient drivers, but they don't pay my fuel bill!). Does anyone out there have this kind of setup but with a 3.55 gear? I am thinking about changing my ring and pinion gears to increase the fuel mileage. Any increase would be beneficial with the cost of diesel fuel as high as it is these days. All comments will be greatly appreciated
Thanks,
Rob

Awesome mileage....I don't know if you could do better, but with the 3.55 gears you might be able to go faster with same fuel usage.

You might re-ask your question at www.turbodieselregister.com, it's exclusively a Dodge Cummins website.