I'm going to run somewhere between a 29" and a 30" tire.

I have the 54rwrew234r w/e transmission, 5th gear is 0.67:1. My rear end is 3.55 with the factory LSD.

I'm looking for shorter rear end gears. Could I get some advice? What kind of mileage drop will I see, does it make sense for me to get them? I'm in a 04 quad cab, 2wd, 4.7. looking for anything between 3.55 and 4.56.

 

3:92s are common in Dakotas and that will help your acceleration a bit but if you are really looking for more acceleration 4.56's are the way to go. I'm not sure what gears are made for our rear diffs in between 4.56's and 3.92's.

The mileage drop you see will depend on your driving conditions and style. If you do a lot of city driving you won't see a drop most likely and will probably see an increase. But if you drive on the highway I would expect a minimal difference with 3.92s, and maybe 2 mpg with 4.56s. This is an approximation however.

I know Playmaker and I have the same truck for the most part except he has a 3.92 rear gear and I have a 3.55 rear gear and there really isn't any difference in the mileage I see and what he sees.

 

if it was all HW I think bpark would win and all country/city I would win is what it comes down to and thats with a very small difference I feel, just because the higher number/lower technically number helps with getting it moving.

 

Exactly and that is why I bet, on average, we see very similar numbers.

 

the only thing I can think of that even's it out now is my 32's...you still have 31's right?

 

yeah, 265/70 which turns out to be just shy of a 31" but pretty much.

 

I'm thinking about going to 3.92 or 4.10

w/30" tire @ 70mph
3.55 1865
3.92 2059
4.10 2154
4.56 2395

Locker...LSD...open?...hmmm

 

since your 2wd I'd try to find a Corp 9.25 with LSD with 3.92's in a junk yard. It's what came in these trucks (what mine is) and should be a pretty straight forward swap. Im not 100% sure but I think the ones in the rams may be a tad wider but if not one from a ram, jeep ect would work. Of course if you want to rebuild yours I say 4.10's and LSD.

 

Stupid question.......if you change rear gears (on a 4X4) don't you also have to change front diff gears as well??

 

Yes, you do.


It's about 500 for a 9.25/3.92 for one at a junkyard...decisions.