Axles

[Jeepmedic46]

Starting to save for axles. Pending nothing happens. Thinking of Dana 44 in the front with 4X4 hubs and a 9” rear end. 4.56 gears. Would that be to much for my XJ? I’ll be running 255/75/17. Thinking of dropping down to 15” wheels.

 

[SkweekyXJ]

Starting to save for axles. Pending nothing happens. Thinking of Dana 44 in the front with 4X4 hubs and a 9” rear end. 4.56 gears. Would that be to much for my XJ? I’ll be running 255/75/17. Thinking of dropping down to 15” wheels.

I would say your choice of upgrading axles to only go to a 32" tire doesn't make sense, I would beef up the ones you have (unless Dana 35) instead. Keep in mind you lose ground clearance going to bigger pumpkins. Also, why the 17" rim? You lose out on sidewall height, and this contact patch length when airing down. I chose 16" wheels because then I could get load range E KO2s, which are a 3 ply sidewall AT tire, plus I can do a wj knuckle swap later without having to worry about new wheels to fit bigger brakes. Gearing I can't say for sure, but running a manual trans, unless you're rock crawling I don't feel a need for anything deeper than 4.10s.

 

[Dilldog]

It will be expensive to get the correct width 44 and 9" axles for your Jeep, only factory set up for that would be early Bronco. A much cheaper and esier to find option would be looking for a later CJ Jeep, lots of those came with the model 44 front and an AMC model 20 out back. Thats the axles I used to swap under an 89 S10 that we put a 350 in and put on 36s, it was a killer set up (used 57" chevy springs out back and the rear springs from a ZR2 S10 up front). Also pay attention to which side the transfer case drop is on for your front axle.
But honestly, the tire size you say you want is only a 32" tire, a model 35 rear axle should hold that without any big issues, especially behind an automatic transmission. Really the only issue I ever had with my 35 rear diff. were the spider gears blowing out which was fixed with a lock rite. I was running 31s and seriously hammered on my TJ (the 4.0L makes peak power at 4800rpm, so I spend A LOT of time at the rev limiter, lol) and I had a manual transmission.
Running 32s you may not need 4.56s, but honestly the lower the ratio the better to a point. The transmissions in the XJ are not the most stout unit in the world so taking some stress off of that with a lower final drive ratio is a good idea. Also a lot of people mistakenly think the 4.0L is a low rev engine, they like the revs (peak HP at 4800rpm and peak torque at 4500rpm if I remember right) so winding them out isnt a bad thing. And I wouldnt worry about fuel efficiency, Jeeps and the 4.0L arent really made for fuel millage, lol.
Finally I would recommend getting a trans fluid temp gauge to keep tabs on how the trans is doing. I know I caught some hell for suggesting this in another thread, but its sound advice, if the transmission isnt staying in over drive or in torque converter lockup, turn off over drive drive until youre up to a sustained highway speed (If it still wont hold then youll need lower gears or smaller tires, but with 4.56s and 32s youll be good). This will help keep fluid temps down by limiting up and down shifts and torque converter lock and unlock. Also downshifting for hills is good practice as well. When I pulled big hills in my TJ I would drop it down into 3rd (5 speed manual) a lot of the time and pull hills up around 3500rpm. If everything is in mechanically sound shape you will be doing the engine a favor by winding it out, and in your case the transmission a favor too.

 

[SkweekyXJ]

It will be expensive to get the correct width 44 and 9" axles for your Jeep, only factory set up for that would be early Bronco. A much cheaper and esier to find option would be looking for a later CJ Jeep, lots of those came with the model 44 front and an AMC model 20 out back. Thats the axles I used to swap under an 89 S10 that we put a 350 in and put on 36s, it was a killer set up (used 57" chevy springs out back and the rear springs from a ZR2 S10 up front). Also pay attention to which side the transfer case drop is on for your front axle.
But honestly, the tire size you say you want is only a 32" tire, a model 35 rear axle should hold that without any big issues, especially behind an automatic transmission. Really the only issue I ever had with my 35 rear diff. were the spider gears blowing out which was fixed with a lock rite. I was running 31s and seriously hammered on my TJ (the 4.0L makes peak power at 4800rpm, so I spend A LOT of time at the rev limiter, lol) and I had a manual transmission.
Running 32s you may not need 4.56s, but honestly the lower the ratio the better to a point. The transmissions in the XJ are not the most stout unit in the world so taking some stress off of that with a lower final drive ratio is a good idea. Also a lot of people mistakenly think the 4.0L is a low rev engine, they like the revs (peak HP at 4800rpm and peak torque at 4500rpm if I remember right) so winding them out isnt a bad thing. And I wouldnt worry about fuel efficiency, Jeeps and the 4.0L arent really made for fuel millage, lol.
Finally I would recommend getting a trans fluid temp gauge to keep tabs on how the trans is doing. I know I caught some hell for suggesting this in another thread, but its sound advice, if the transmission isnt staying in over drive or in torque converter lockup, turn off over drive drive until youre up to a sustained highway speed (If it still wont hold then youll need lower gears or smaller tires, but with 4.56s and 32s youll be good). This will help keep fluid temps down by limiting up and down shifts and torque converter lock and unlock. Also downshifting for hills is good practice as well. When I pulled big hills in my TJ I would drop it down into 3rd (5 speed manual) a lot of the time and pull hills up around 3500rpm. If everything is in mechanically sound shape you will be doing the engine a favor by winding it out, and in your case the transmission a favor too.

Just an FYI, peak torque on the 4.0 varies by year. Once you're at year model 97+ the peak torque is at 3000RPM.

 

[Dilldog]

Just an FYI, peak torque on the 4.0 varies by year. Once you're at year model 97+ the peak torque is at 3000RPM.

Gotchya. My TJ was a 99, all I remember for sure was that peak HP was right before the rev limiter, so I spent a fair amount of time in the upper 1/4 of the rev range on mine. Maybe it was 4500rpm for peak HP and the rev limiter was at 4800rpm. Now youve got me wondering. All I remember for sure was it ran really well in the upper part of the rpm range, and it made lots of people cringe, which as someone who has experience building engines, made me laugh.

 

[Jeepmedic46]

I’ll rethink my choice of axles. My goals are to be able to do some of the Northeast Adventure trips and some of the Vermont Overland trips. The Jeep came with the 17” wheels. Want to go down to the stock 15”. Would like to go to 33” tires but don’t want to cut the fenders. Jeep has a Rough Country 4.5 lift.

 

[Dilldog]

Honestly, a buddy of mine wheeled an XJ perty hard on 35s with 4.88s and the factory 30 35 axle combo. He just had upgraded axle shafts and lockers. Just dont go hammering on the rig and youll be fine. I really think for most "overland" style off road that the factory axles with some upgrades will be fine.

 

[SkweekyXJ]

I’ll rethink my choice of axles. My goals are to be able to do some of the Northeast Adventure trips and some of the Vermont Overland trips. The Jeep came with the 17” wheels. Want to go down to the stock 15”. Would like to go to 33” tires but don’t want to cut the fenders. Jeep has a Rough Country 4.5 lift.

From what I've experienced, one main reason people need to trim going to bigger tires is the width of the tire and the offset of the wheel. If you stick with a narrow the like they were designed for, with an original offset wheel and width they'll tuck in the wheel wells just fine. The vehicle will drive better too.
BFG makes the KO2 in 33/10.5r15, a "33in" tire load range C, and in 235/85r16, a "32in" tire load range E. Both are options but I like 3 ply sidewalls.

 

[SkweekyXJ]

Honestly, a buddy of mine wheeled an XJ perty hard on 35s with 4.88s and the factory 30 35 axle combo. He just had upgraded axle shafts and lockers. Just dont go hammering on the rig and youll be fine. I really think for most "overland" style off road that the factory axles with some upgrades will be fine.

Exactly, ones driving style makes a big difference in how's things get destroyed, especially when locked. Wheel spin/hopping is the primary way to break something.

 

[SkweekyXJ]

Gotchya. My TJ was a 99, all I remember for sure was that peak HP was right before the rev limiter, so I spent a fair amount of time in the upper 1/4 of the rev range on mine. Maybe it was 4500rpm for peak HP and the rev limiter was at 4800rpm. Now youve got me wondering. All I remember for sure was it ran really well in the upper part of the rpm range, and it made lots of people cringe, which as someone who has experience building engines, made me laugh.

Yup, peak hp is like 4600, and redline is maybe 5k. Rarely find myself needing more than 4k rpm myself.

 

[Jeepmedic46]

From what I've experienced, one main reason people need to trim going to bigger tires is the width of the tire and the offset of the wheel. If you stick with a narrow the like they were designed for, with an original offset wheel and width they'll tuck in the wheel wells just fine. The vehicle will drive better too.
BFG makes the KO2 in 33/10.5r15, a "33in" tire load range C, and in 235/85r16, a "32in" tire load range E. Both are options but I like 3 ply sidewalls.

I want to keep the tire narrow like it’s supposed to be. My plan is to find a Set of 15” aluminum wheels and sell the 17” wheels and tires. Plenty of tread. Not sure if I should stay with the M/T or go with the A/T. All my pickups had the A/T load E. That might be to heavy of a tire for the XJ.

 

[Dilldog]

Yup, peak hp is like 4600, and redline is maybe 5k. Rarely find myself needing more than 4k rpm myself.

Ill be honest, I just like the sound of engines running right at peak

Exactly, ones driving style makes a big difference in how's things get destroyed, especially when locked. Wheel spin/hopping is the primary way to break something.

Yeah high rpms and tire hop is how I launched 2 sets of spider gears through the diff cover on the my TJ.

 

[Dilldog]

I want to keep the tire narrow like it’s supposed to be. My plan is to find a Set of 15” aluminum wheels and sell the 17” wheels and tires. Plenty of tread. Not sure if I should stay with the M/T or go with the A/T. All my pickups had the A/T load E. That might be to heavy of a tire for the XJ.

I think BFG still makes a 33x10.50R15. As far as load rating, an E rated tire is overkill on an XJ, but it wont hurt anything. It will just stiffen your ride and make ideal tire pressures different.

 

[SkweekyXJ]

I think BFG still makes a 33x10.50R15. As far as load rating, an E rated tire is overkill on an XJ, but it wont hurt anything. It will just stiffen your ride and make ideal tire pressures different.

They do still make the 10.5 wide option. Stock width was 225/235, which is what I'm running now. I've attached a pic of mine with 235/85r16 on stock ICON wheels. I don't notice them being any harsher, I run 28psi front, 30psi rear, and the rig weighs 4200lbs. I am running slider boxes for the rear leafs though. Lift is 3.5" RE.

 

[Jeepmedic46]

They do still make the 10.5 wide option. Stock width was 225/235, which is what I'm running now. I've attached a pic of mine with 235/85r16 on stock ICON wheels. I don't notice them being any harsher, I run 28psi front, 30psi rear, and the rig weighs 4200lbs. I am running slider boxes for the rear leafs though. Lift is 3.5" RE. View attachment 131827

Nice looking Jeep. What are you running for gears? What size tire would you recommend? I have the 4.5”lift?

 

[SkweekyXJ]

Nice looking Jeep. What are you running for gears? What size tire would you recommend? I have the 4.5”lift?

Right now I'm running 3.55, but with a manual transmission. I expect myself to likely go to 4.10 sometime in the future, but nothing deeper. If you are wanting to avoid any trimming/nasty rubbing I think 32" is pretty accepted in the XJ community as being the sweet spot for that amount of lift, and if you stay to a 235 width, it's even less likely to have issues. Might just have to minutely adjust steering stop to stop rubbing the lcas at full lock. If you look at overlanders around the world, it's a common size. I would recommend AT tires over MT unless you're going to be in the mud a lot. Both for overland performance focuses and ride quality.

 

[M Rose]

@Jeepmedic46, I had a 89 Cherokee when I lived in upstate NY, I bombed around up there year around with the stock Dana axles without an issue. I wouldn’t touch the axles until you go above a 35” tire and more than 6.5” of lift. The only thing I would do to the stock front Dana 30 is get a Posi-Lock cable operated CAD. The vacuum operated CAD that comes stock is prone to failure and causes your front axle to not engage. This becomes very common in cold conditions when condensation builds up inside the CAD and then freezes not allowing the axle shaft couplers to engage under vacuum pressure.
Secondly if you feel you must do an axle swap go one tons, a lot better after market support and you can actually get a kit for reasonably cheap to put junkyard axles under the XJ. But again, I say stay as close to stock as you can

 

[Downs]

For that tire size I wouldn't bother spending the time and money trying to get non Xj axles under there, save that money and put it towards fuel and getting out here. I can't remember what your axles are from your previous threads but the Dana 30 is actually quite a good axle and you really aren't gaining much strength by going to a 44. You get a larger ring gear not much else.

If you have the D35 in the back just find a Junkyard or part out 8.25. No fabrication required they bolt right in and offer plenty of strength for the vast majority of XJs out there. 97 plus 8.25s have 29 spline vs 27 spline axles on the earlier ones and have a larger selection of traction adders.

 

[Jeepmedic46]

I have a D35 in the rear. I’ve heard they aren’t a good axle. Going the 8.25 would be a better option. Less money. Would like to get rid of the drum brakes in the rear.

 

[MidOH]

Keep your Dana 30 front. Beef it with better axle shafts that eliminate the weird YJ axle splitter. Put a front locker in when you regear. I like the Yukon Grizzly the best.

Get rid of your rear Dana 35. It's worthless. Not even worth the cost of regearing. The fact that modern jeeps still include it, is a complete travesty. The Ford 8.8 is an extremely popular, and very cheap swap. Find a custom axle builder. My axle guy rebuilds axles for half of the retail prices you see for aftermarket axles. Most of the XJ guys here are running Truetracs or spools in the rear. Very few Grizzlys or Detroits in the rear of XJ's. Selectable is nice in the rear if you're rich, or it's a very nice XJ worth that kind of money. But spools are the most popular for the XJ guys here. (hey if the 35 is long gone, and you have some real beef now, why not ?)

My axle guy can cut down a Dana 60 for cheap. But generally Ford 9'' and Dana 60's cost extra. Used core availability, swings the price tag wildly. 8.8's are available everywhere in junkyard Mustangs.

Cooper STT's are still my pick for Ohio to Maine.