I've recently began the refreshing of my offroad rig, as it definitely needs some TLC. I have been using 33/12.5/15 size tires, and definitely need to re-assess my gearing. I would like to use a 4.10 ratio, as it would improve the overall performance and seeing that I drive this rig on the road as well. I know that it has a D30 front and a D35 rear, but I'm struggling to find a gear set for the front axle. I've researched that XJ's had reverse cut gears in the front, but don't know if that correlates to high or low pinion... I'm new to all of this, so any and all advice would be much appreciated!

 

I’d research the 8.25 swap for the rear first. It’s affordable and straightforward. This is the time to add a locker if you want one. You only want to do this once.
4:56 is perfect for 33’s in my opinion.

 

Reverse cut would be the high pinion..

 

Is this because the Chrystler 8.25 is a more reliable axle? I should be able to find one in a Upull yard... Affordable is better, in my case! Do you feel the 4.56 will still provide a daily drive-able experience?

 

Yes, 4.56 for 33. 4.10 would be good for 31 Imo. Only reason I will run 4.10 for 33 would be finding a good set of used axle that's already geared 4.10, but I know I will be frustrated when it keep kicking down a gear on highway.

8.25 is stronger than D35, Its direct swap without any fabrication. You can easily find one cheap. The only other axle that is direct swap is the late 80s Cherokee D44. Stronger than 8.25, good luck finding one.

Other common option is Ford 8.8, require cutting the original patch, welding the spring patch and the shocks mount. Stronger than 8.25, easy to find one with disc brake, arguably as strong or stronger than D44.


I personally will either find a 8.25 or 8.8 rear, and a HP D30 front axle before putting money on regearing.

 

Thank you for this! It's hard to get to know all of this information when you're just starting to get your feet wet... Is there anything else to keep in mind? Reliable carrier, etc... I'm trying to set up my game plan before diving in, so I don't miss anything on my first go

 

Absolutley don't waste a single dime upgrading or regearing that Dana 35 rear, swap an 8.25 in. Since yours is a 2000 the front could be a high or low pinion dana 30 so check that before ordering gears, for 33s I would get 4.56 gears.

 

I got 4.1 diff gears with 33 inch tires. Not the best ratio for highway use, livable, but slow going up hill and accelerating. (like driving my old under powered VW Bus)Lots of down shifting in the hills even at freeway speed. Eventually I might go to 4.56, but it is a big job to regear. I want to do it, just is I am time constrained. I do however have a super high ratio low tranfercase gear, which make off roading fine, but with a stock transfer case that 4.11 would be even worse.

 

4.56 for the win.

 

Yes and run the 35, for 99% of xjs its plenty beef.

 

8.25 is good enough for 33, look for the 29 spine one. Nothing much other than all standard axle stuff, get professional to regear if you are not experienced. if one don't know about gear and try to shim it yourself, it might potentially cost four $30 worth bearings every trail and error. (my experience)

You can also search for disc brake upgrade on 8.25. However its debatable rather its worth it or not.

 

Not debatable on the discs. Very much worth it. I've done quite a few.

 

Well worth it if you ever haul anything heavy in the back, or tow a trailer.
After I did the ZJ rear upgrade it was night and day different when I would haul a bunch of sound equipment down the hill to LA.

 

Might be a stupid question, but does the re-gearing with taller tires effect gas mileage a lot? I know that re-gearing and keeping same size tires to improve acceleration (aka, hot rods) hurts it, but I assume the taller tires effectively bring the ratios back down.

And as far as disc brake conversions, are there aftermarket options or is it better to head to the junk yard?

ZJ is Grand Cherokee, correct? Is that a direct bolt on conversion? I'm not a welder...yet.

 

There are some stated that a well maintained and service drum is as good as disc. Logically I don't agree.

But based on my experience, I don't disagree either.

I have done the disc brake conversion too with the 8.8. I don't see noticeable difference. That said I haven't replace the proportional valve, and I don't have hills in my area, nor use much brake with my driving style.