Hey Fellas. 99 4.0 30/35. I've been running my 35's for a while now with the stock 273 gears (correct me if that number is wrong). Power is all right. Could be way better. MPG could definitely be better. How much of a difference would i see if I went with some taller gears ?? Huge power and MPG gains ? Would I be more likely to bust my dana 35? Cost and best place to buy? Install cost? Thanks for your experience!

Too much rubber, too little steel inside. You're living on borrowed time. If its a grocery getter, you can probably suffer for a long time with what you've got. Its probably not worth the expense to install better gearing (but I tend to doubt that you've got 2.73s). You've got to swap out both the front and rear gearsets, and that'll run you some money.

With 35" tires, you won't see real performance until you get beyone 4.10s, with either 4.56 or 4.88s bringing you back to where its fun. Then you get carried away with the fun part and break the expensive stuff you just put in.

The cheapest route for you would probably be to look for a set of already assembled front an rear axles, preferably a 44 rear. If you're willing to trade your present set, you might come out of it OK.

do you have a stick or auto?

3.73 is more like it. With my manual I needed
at least 4.56 for the 35s. This had me reeving
about 300 rpm higher at highways speeds.

An auto would be different.

Yes, I have a manual. I really don't want to switch out the axles. Having the higher gear ratio would lessen the stress put on my weak dana 35, correct ??

quote:

Originally posted by I Love My Jeep:
Yes, I have a manual. I really don't want to switch out the axles. Having the higher gear ratio would lessen the stress put on my weak dana 35, correct ??

if I were you I'd run that combo until something breaks (more than likely the D35 before the D30). Then get a new axle for the rear (D44 or F8.8) see what gears they have in it already and match the front
A stock D44 will more than likely have 3.73 gears, what you've got right now, and a stock F8.8 probably has 4.10 gears, meaning you would only have to regear the front.

HTH

My D-30 front has gone almost 100K with the 35s - I have a D-44 rear and have
had to rebuild it once - align the housing and change out the brackets.

Depending on how you wheel the D-35 will break - and you will find that the
axles shops will not even try to fix it.

Knowing that you start looking for a D-44 or D-60 replacement. If you use
a D-44 you can reuse your brake parts and cables - saves money - if you
jump to a D-60 you will need new brakes and will have to answer questions
like - do I re-axle to 5x4.5 bolt pattern - and keep the wheels - or
move up to 5x5.5 (older jeep) or a 8x8 GM pattern - with bigger wheels.

One advantage of moving to a bigger axle is you can choose to move to a
bigger wheel and get bigger brakes - disks being the most ideal.

I ran my 30 with 4.56s and 37s for year with no issues. I had a D44 rear, but I've seen numerous D35s live long healthy lives with 4.56s and 35s. It all depends on how your use the skinny pedal. If you only know 2 speeds, off and wide open, then your D35 is not going to last you very long.

Out here on the rocks and sand we have a problem with axles without
lockers spinning up when they loose traction - and popping the gear
teeth when the re-acquire traction - that is how I did my gears up.

A locker actually means that you can attack trails slower and never
loose traction - there are a few trails out here that are ball bearing
rocks - about two-four inches in size- that sit on sand bases and
you have to hit them with speed if you do not have lockers - and
then heaven help you - back down - if you don't make them - with
lockers I just crawl up at about 1/2 an mph - or less - and never
risk the gears.

If you have trails like that - do the lockers - at the same time you
do the gears. I think the reason my D30/44 made it so long was just
going really really slow.