my truck is a doggy turd now with my new tires i want to chang my gears but dont know wat ratio to put in. its got heavy *** 34's on heavy *** 20's. i think its got the high highway gears in it now from the factory. i mud drive in town and the highway wats a good ratio for all of that cause im gettin 9.6 mpg and i want a little better.

 

Do a search on here, most people swap to 4.56s

If you have a 4x4 you will need to do both front and rear diffs, so it will be pretty expensive.

 

like he said, 4.56 are your best bet (and biggest you can fit in the front diff). Same if not better gas mileage, alot more low end....ill be doing it next spring. Lockers make it quite a bit more expensive but so much more effective

tons of threads on this...the search button is your friend!

 

Yeah lots of guys like 456. Ive got them in my truck as well.

 

how will the 4.56 do on the highway anybody have them in, wat kind of rpm's are they runnin at 70 mph

 

I get about 2 mpg better in town, maybe a 1 mpg loss on the interstate, but really only if I'm traveling up over about 75 mph since the swap from 3.92s to 4.56s.

Low end is night/day different with the gears, single best mod I've done.

I tach right at about 2100 at 70 mph...

 

I plan on gettin mine done in 3-4 weeks and am not 100% sure as well weather 4:10 or 4:56 (Have 3:55 like OP) would suit my needs as I drive 80 MPH on our Trans Canada 4 Laner but from what I have read on here since joining if I don't go 4:56 I'll be regretting it (and prolly be chastized "I Told You So").

So worst case if I find the revs to high on the highway I can always go bigger Tire!

I can assume Hammer your Tires are 35's? as you guys have said its better for the truck to be close to the Sweet Spot anyways!

 

Dan,
I don't run 80 mph, but usually around 65-70 with 4:10 and 30.5" tire. I wish I had gone with 4:56. Bigger tires won't have a problem running 4:56 gear IMO.

 

Thanks for the Info Greg.

So Outcast, 4:56 are what the Guys are all gonna Tell You on here! Good Luck Man.

 

Outcast, the basic rule is suppose to be 4:10 up to 33" tires and anything taller 4:56. With a 4.7 engine and larger than stock tires I would say 4:56 will bring her to life. Good luck....