Just got a '06 z71 crew cab, 5.3 with a 6" lift and 35's with a 20x10 wheel. Sharp ride but it's sucking the hell out of some gas. I traded a '03 Tahoe for it that had 17's and 35's and averaged 12-14mpg. My truck is maybe getting 10-12.

So I'm thinking about putting in gears. I don't haul a lot and I don't mud ride in it. It's my everyday driver. So I'm wanting something to help ease the stress off my transmission and help with my mpg. Should I go with 4.55 or 4.88??

 

maybe i am missing some info; how will going to a higher ratio improve mileage. What are you running 3.73?

anything jacked up that high with huge tires has terrible aero drag.

 

I know it's going to get bad, but I've talked to a few people same they said that changing the gears will help the strain on transmission and will help
Out the mileage by 3-5 gallons. Idk tho that's why I'm asking.

 

Going to a higher numeric set of gears WILL improve fuel economy and MORE IMPORTANTLY it will help relieve some of the stress that the transmission sees. Your truck most likely has a 4L60/65E in it-one of the weakest transmissions GM has ever produced in their history. Those 35's are seen by the transmission as if you are pulling a trailer around behind you every mile you drive. This is why your fuel economy is so bad. And those big tires are also why you are going to see a drastically reduced transmission lifespan.

I would highly recommend the 4:55's. If you plan on towing-which I do not recommend under any circumstances-you should step up to the 4.88's.

 

i could see that in city driving or towing but on the highway the big tires lower the final ratio and would help mpg.