I’m sure this question has been asked a lot, but I never quite found the answer I was looking for on google. I have a 99 Xj auto and i was wondering if a 4.10 or 4.56 would be better when i upgrade tires to the 31-33 range. Once again it’s an auto, and i’ve heard different opinions on the regearing for autos. Mostly city/ highway driving, usually in the 45-60 range. I’m mostly concerned about power and almost as concerned about gas mileage. Also, if anyone has any tips for the cheapest ways and best kits to do this i’m concerned
about that too. Any input helps, thanks.

Edit: It’s a daily driver (that’s why i’m concerned about power and mileage) and I offroad frequently now but i plan to offroad even more after the tires/ lift.

 

I would go with 4.56s for 33s. I got my USA standard 4.56 gears online from Ron's Machining Service, they have been fine so far.

 

I had 4.56 with 31s, 33s and 35s and I've been happy with them. I don't want to go to 4.88 because of the pinion size and I'm putting a stroker in now so it doesn't matter anyway now, should have plenty of power.

 

So with the 4.56, what axle swap options do i have vs a regear? which would be cheaper and which would be better?

 

Depends on if you get a good deal on the gear or if you can get a better deal on axles somewhere. Depends on if you can install parts yourself or if you're going to pay someone to install them. Depends on what the final goal is and if that goal will eventually change or not. There are too many factors to say x is cheaper than y.

 

I have 4.88 with 33's and lockers front and rear. Plenty of power and has held up for over a year now but I'm not overly abusive on it either. About 2500 RPM's at 65 MPH.

 

4.10 for 31's, 4.56 for 33's

4.10 for highway, 4.56 for city

4.10 for mileage, 4.56 for power


Go for the deeper gears (4.56). It will give you the option to go bigger tires and will be better offroad. Sounds like you'll grow into them.

 

FYI.

I've got D30/c8.25. Planning to run 35's. Currently gathering parts and tools. First time installing gears, hopefully I don't screw it up.

Purchased from Ron's Machine: 4.56 front/rear, USA gears - Elite master kit $410 shipped. Available through their website or Ebay.

For axles and lockers - Yukon, currently has a rebate program until the end of the month. (You'll have to confirm.)

The following is available on Amazon.

Currently prices (they fluctuate)
D30 - $445.98. shipped
8.25 - $256.20 shipped
Grizzly - $475 shipped

Good luck with your build.

Joe

 

Thank you, all helps a lot. If regearing isn’t an option, what axle swaps would work well? I heard some xjs have the 4.56.

 

The only easy swap would be a high pinion Dana 30 front and 29 spline c8.25 rear out of a 97-99 four cylinder (2.5 L) Cherokee without ABS. They'll be the same axles you have but with 4.10 gears. They can be pretty difficult to come by though. Some older XJ's did come with 4.56 gears from factory but they're very rare.

Other axle swap options would be just bigger axles, only would make sense if you are going 35"+ tires.

If you want lockers, now is the time. Full case style lockers (not lunchbox style) have the ring gear bolted to them (replacing the carrier) which means setting the gears up. Do them at the same time as a regear to avoid doing the labor twice.

 

That would be the older 4 cyl with the AW4 auto....they had 4.56 gears.

I've seen 1 in the 10 yrs or so I've had a cherokee.....was gonna buy it, but I needed the trans, and he wanted too much for it with a questionable transmission (quirky shifting).

it was also a 2 door......with a pretty rough interior & body

 

The 8.8 is my favorite. Find one from a 98+(?) Ford Explorer and you get disc brakes. You'd still have to regear it but its an easy axle to work on.

 

My plan is Toyota elocker axle rear with 4.30s and then a trail gear housing in the front with a 4.30 elocker diff from the junkyard. Selectable front and rear lockers with pretty good gears, more clearance, stronger axles, and locking hubs

 

The high pinion Dana 30 that comes in the XJ is close to the strongest direct bolt in from a junkyard. But I believe you would already have one in your Jeep so you're close to being there.

The only stronger axle that would almost bolt right in is the Dana 44 from a TJ Rubicon (2003-2006). You would need a shorter driveshaft to go with it but the brackets are all in the right place. It comes with 4.10's and an air locker.

The only stronger axles that would bolt right in are custom aftermarket axles. They are far from being cheap. But they're a ton stronger.

The 29 spline 8.25 rear axle is in the same strength neighborhood as the Dana 44 and Ford 8.8. The 8.8 swap is relatively easy and it gives you factory disc brakes but that's really the only reason to do that swap. But the swap involves minor cutting and welding on the axle to get the spring perches and shock mounts where they need to be. The rear drum brakes aren't terrible and a disc brake upgrade isn't going to be a night and day difference. Maintenance on disc brakes is easier and you don't have to worry about adjusting them periodically like you do on drum brakes. But the kits cost upwords of $800+ once you factor in the kit and the new parking brake cables.


Pretty much every other junkyard axle is going to require fabrication of the brackets on the front and possibly dealing with an axle that's a lot wider than what comes under your Jeep now. If you're a good welder/fabricator, you can do the work pretty easily.

 

The air locker would require the factory pump since it uses such a low pressure most aftermarket pumps are way too much, and it's very easy and cheap to do a disc brake conversion on an 8.25 with junkyard parts.
Another note
8.25 is 29 spline c clip
D44 is 30 spline non c clip
8.8 is 31 spline c clip
So 8.8 is a little stronger than d44 but when a shaft breaks it's coming out where a d44 shaft will be retained unless broken right at the wheel bearing. On the topic of d44 they were factory in Cherokees in the very early years of production.
Axle swaps get very complicated very quick if you aren't 100% prepared