With stock gears - quite a few. Plus your drivetrain (especially your trans) will be stressed more (not a good thing). With the right gears though, even 35's can be run with not that bad of mileage. Big tires have a great deal more rolling resistance, weigh more, and a lifted truck isn't exactly aerodynamic, so you will probably always lose some mpg's with a lift and 35's. But gears go a long long way to make it much more tolerable from both a performance standpoint, equipment longevity standpoint, and mpg standpoint.

Ill get the gears done when I get my income tax I recon.Just trying to see what the loss will be.No biggie didnt buy her for her mpg just wondering.

Also thought I should mention this truck runs mostly on the hwy very little on the county roads&I dont tow anything....I guess I can get em&run em for a few months&if I feal I need gears Ill get em them?

You'll need them no question about it. Mine as well keep the od off too.

Oh&I usually never go over 70

just put the tires on and your be happy... when i put the 35s(okay 34.9s) on my dodge i love how it looked so much. i want to get bigger tires now much bigger tires

but for what your lose your gain back in looks and the girls will like you more

I just got a quote on Yukon 4.56's from a local shop today. Front is $395.00, rears 450.00, shipping 50-75.00.

what do u think would be a good gear if i ran 40s on my dodge? 4.88s? i have 4.10s atm with my 35s

For 40's, you will want 5.13's. Since you have a 2500, you probably have D60's, so you can go there.

I'd go steeper than that with 40's personally, I like the power lol. 5.38's would be better.