I have a 99 sport, 4.0L auto

I am planning on ordering 4.56s this weekend and soon getting 35s (running 32s as of now) and I was wondering if this is the most ideal set up for drivin to the trails and home? I've seen some people say 4.88s are better?

Thanks

Use the technical article submission section only for technical writeups.

4.88's will be more ideal but depending on what rear axle you have 4.56's will be your limit.

4.56 will do fine 4.88 might do alittle better if you leave your motor stock and ever want to go up in tire size. i run 34" ltbs and im going to put in 4.56 but i have no intention in going over 34"10.50"

Copied from another forum:

Current tire size/new tire size =current gear ratio/new gear ratio

This simple formula will allow you to figure out what ratio will get you back to your current performance.
For instance, let's say you have stock 3.55 gears & stock tires and want to go to 33" tires.
Stock XJ tires are about 27" tall so:

27/33 = 3.55/new gear ratio

Cross multiplying (thought you'd never use algebra again?) gets you this:
33 X 3.55 = 27 X new gear ratio

117.15 = 27 X new gear ratio

117.15/27 = 4.34

In other words, 4.56 gears (the closest avail to 4.34) will give you slightly lower gearing than you had while stock.
From here it's up to you where to go.
If stock performance is fine stay with 4.56. If you want a little more low end grunt, go to 4.88. If you want to murder the rocks go to 5.13 or lower.

yea proportions ive uses sooo many times.. pays not to be ignorant haha. u got like 4.10s ill bet dont you in that 2.5?

Yeah, I've got 4.10s behind my 4 angry squirrels

4.56s are just about perfect for 33" tires (auto tranny). However, as my XJ has gotten heavier (especially when the ARB bumper and winch went on) I begin to wish I'd gone with 4.88s. There is no way I would run 4.56s for 35" tires. Just MHO, of course.

you always hear of people wishing they went lower, but you never hear of people wishing they went higher.

go 4.88's

the extra gear also helps turning the added rotating mass

I was planning to run 35s, and running an 8.8 in the rear and D30 in front.

Then 4.88's sounds like the way to go for you.

I would still like to be able go on the interstate though...and I will not go larger than 35s

4.88s PERIOD!!
I have 4.88s with 33" tires, and at 75mph I'm sitting at 2600 RPM, and can accelerate very well. Trust me get the 4.88s, really!

What kinda MPGs you gettin? HWY and city

Not really sure yet. I just got the new speedo gear a couple of weeks ago or so. I got about 200 miles to the first tank, and some of that was wheeling. I hope to get over 200 on the next tank. I have a 15 gallon tank, FWIW! Hope this helps!!

Thats ~13/gal I think 4.56s will be higher than that