jsowards

Looking to regear my 98 XJ.

Specs:
4.0 I6
AW4 Automatic
3.55 gears
4.5" lift
33x12.50 Duratracs (Have no intentions of going any bigger as this is plenty big enough for my needs)

I have done some extensive research and some people say that 4.88 gears will yield better mileage all around than 4.56 gears. They say that the 4.0 likes higher RPM's where it is more efficient for MPG's. Is this true? Which gears will get me better mileage? MPG experiences with these combinations would be helpful especially those of you who have calibrated the speedometer for correct mileage.

Note:
Speed limit where i live is 70 MPH, Roads are relatively flat, and I am not a leadfoot when driving my XJ (after all its not a sportscar)

Metmknice

If you ever plan on going to larger tires, 4.88s for sure. If in doubt go taller. I would go with 4.56's. Higher rpm is not a necessity. Between 2200-2700ish I believe is where you want to be. I have 4.10s with 31's and run about 2500 @ about 70

jsowards

I have no intentions of getting 35's. The 33's are plenty large enough for my use.

rideordie66

in my experience the higher rpm means more gas used to travel the same miles. You may get there quicker but you use more gas driving at high rpm. Its all in your foot really tho. A steady pedal is better than going up and down.

SeriousOffroad

4.56
www.grimmjeeper.com

n_a_i_w

im running 35's with 4:88 gears. i can cruise at 65 with 2400 RPM's .. I would recommend 4:56's for 33 inch tires

ct67_72

I would go 4.88. 4.56 would put you closest to stock, but who says stock was the best anyway. It mostly had to do with lowering rpm for emissions purposes.
I have 4.88 and 35's. I wish I could run 5.13. I think it would be perfect, and that would be close to 4.88 with a 33.
I can't say your mileage will be better, but the power is nice. Being able to gain speed uphill on the highway without downshifting is nice.

mikeXJ1020

I have 4.88s and 35s. It sweet but dont really see how much difference 4.56 to 4.88 would be. Thats like 3.55s to 3.73s in a sense. Anyway I would have gone with 4.56s because the pinion gear on the 4.88s is really small. but I bought the front diff with the gears in it already.

jsowards

4.56 on 33's sounds like what I will do the 3.55's are terrible with 33's I could ride my bike faster.

dogger15

You know there is a thread that's named regearing for 33s on here that's still a pretty new one

jsowards

yes I have read the entire thread and still no solid answer on MPG difference just a bunch of personal preference.

Dan91

I plan on doing 4.88s with my 33's it'll be nice to have a the extra torque.

mikeXJ1020

If you want good MPG get a Honda.

Just sayin.

Also your not really going to see much difference between the two. Your talkin minimal differences. Also When I had 33s and 3.55s I got 10 mpg. Now I have 35s and 4.88s, I was looking forward to better Mpgs and guess what, still get 10 mpg (maybe 12 if im really nice to her) lol. And Ive done multiple tests to see my speed limit to make sure im correct (GPS and what not)

KCjeeper

My last jeep had 355s an 33s got **** mileage my new jeep I got 35 456 gears gets better gas mileage has plenty of power I agree if u want good gas mileage u got the wrong rig buddy but all depends if u hammer down or drive normal

Demolition_x

I have 4.88's and 33's and its great around town. On the highway it sucks. I try to keep the rpms at 2500 (65mphish) or so but im still getting passed. I always seem to look down and see my rpms just shy of 3k. I hate seeing the rpms that high but so far no real bad side effects yet on the motor. No idea what my mileage is since I havn't changed the speedo gear yet.