Referring to an earlier comment "impressed with the torque for offroading"; I am just letting you know Diesel + Mud = sink, in general all diesel trucks are HEAVY. REALLY HEAVY, if you want to go offroading get a gas truck, much lighter, otherwise stick to the pavement.
I've had my 1996 Dodge 2500 diesel 4X4 since it was new. It not has almost 200,000 miles and all I have done, other than routine brake bad changes and fluid changes, is replacing the clutch. It still runs exactly the same as it did the day I got it.
I don't know how you drive, but with the manual transmission, I get 16-18 mpg city and up to 22 highway. And that's what my brother gets, and he has the automatic transmission.
I think you may be abusing your truck if you're having that much trouble with it.
I am on our second Dodge 2500 SLT Laramie 2 X 4 with a 12 valve Cummins. We bought the first one at 179,000 Km. and sold it at 355,000. Included in the mileage were one trip across Canada and two down to southern Arizona/Mexico towing a 25' 5th wheel. The only repair was the exhaust - changed ahead of time to put in a 4" system and a K & N air filter. We bought the second one with 89,000 in Oct. 2006 (not a typo!) and now have another trip to Mexico and 141,000 Km. on it. Mileage is 25-27 mpg. light and 11-13 towing. Very happy with the unit and it gives us nothing but a feeling of security when crossing Nevada or the Mojave desert. I would buy another but this one will likely outlast our travelling ability. Extremely happy with the whole package!
I also have a 1996 Dodge diesel 4x4. OK, so the paint sucks a bit, but other than that, I have to say it is one of the best trucks that I have ever owned. 209,000 miles and only routine maintenance: oil, shocks, gas filter, brakes, ext. Routine Only. It also has 315/75/16 on it and still getting 20-23mpg on long hauls. I use her every day for work, play, hunting, towing my family of six. She ain't no race car, that's a fact, but it's the only truck I have ever got that BIG of meats on with only a 2" lift. I would buy another one with four doors if could afford it. Still has the stock trans too.
And when he said 140 HP. Ha.
This must be someone driving a Chevy wishing it was a Dodge! As long as you don't dog it you'll get amazing gas mileage out of the 360 Magnum. Proud to say mine's running like a top and I wouldn't trade it for ANYTHING.