Not much at all when Jeep got rid of it in the 90s there was no fuel mileage drop, same goes for the 02 Ram HD. Maybe .1 mpg at the most, it doesn't take that much force to spin the front axle and driveshaft. My F250 has lockout hubs, and my fuel mileage is the same with the hubs locked.

 

Yeah, I did the conversion from full-time 4wd (np203 t-case) on my old blazer, to hubs, and a part-time kit in the t-case..... My gas mileage didn't change either.... Of course, it really didn't matter what I was doing with the blazer. It got 11MPG regardless of how many people/cargo was in it, or what I was towing behind it......

 

I'm going to compare my gas mileage when I do the swap. I only lost .4mpg with 37s and 3.55s

 

What kind of driving do you usually do? Are you mostly freeway? or surface streets? I could see how the big tires might actually help on the freeway.......

 

50/50 I would say mostly rural roads with redlights about every city block

 

How in the world can you turn 37s with 3.55???? I can barely move 32s

 

It was a Cummins 6spd but when I swapped in the 360 auto only thing I did was short headers, new timing chain cloyes, msd coil, the plenum fix with an aluminum plate. She will roast the tires to if I power brake it, an will chirp them if I gun it. I'll see if I can post a video from my snapchat. Have to upload it to YouTube, excuse my talking but my buddy didn't think it would do it.

 

Here it is. Btw these are 1500 axles under my 2500 with a trak-lock that has 170,000 miles on it so it doesn't engage right away. Add me on Snapchat (if you have one) or follow me on Instagram to see the stupid stuff I do and the truck takes it. I have a video of me jumping the truck to lol. Have to show those Ford and Chevy owners!
Here it is:

 

You swapped a 360 auto in place of a Cummins 6 speed, why on earth would you do that?

 

Not a diesel fan at all. I ran it for a bit wasn't impressed. It came with the factory 24V and 6spd and came with a spare 12V and auto. He had some major work done to both of them. I'm swapping in either a 5.7L or 6.4L Hemi into my truck seeing as I have both. Which ever I choose it will make at least 750hp and 900ft lbs of torque.