Rear Differential

flman · **Posted:** Mon Dec 29, 2025 8:09 pm

I had a transmission leak that I put off and added fluid, in the meantime my input shaft seal went bad on the rear differential, so I never thought it was a new leak, it was ran low, and now the differential is noisy under load, and quiet on coast. Would you just put in a new ring, pinion, or should I be concerned about other problems like bearings? Maybe I should see if anyone had a dead CRD here, that wants to sell the rear end?

BTW, my Jeep is getting ready for it's 20th anniversary, I had it since new.

03black · **Posted:** Mon Dec 29, 2025 11:01 pm

Gears might be cooked but, no way to know until you open it up. As for the bearings, yeah they are shot and the will all need to be replaced. You'll need at least a master rebuild kit with all new differential bearings/cups, front and rear pinion bearings/cups and pinion seal. Since your in there might as well change axle bearings and seals too.
Job is not hard to do, lots of youtube videos on how to rebuild the Chrysler 8.25 axle. You'll need some special tools to set backlash. Backlash is set with adjuster nuts so no need to worry about shims. Service manual has everything you need to do the job.

Note: You can use any rear axle from a 02'-07' jeep liberty provided it has the same gear ratio. CRD gear ratio from the factory was 3:73 in the states. 06'-07' jeep liberty had 4 wheel ABS meaning that you have sensors at each wheel. 02'-05' had 3 wheel ABS so the sensor was on top of the differential. Otherwise, everything is the same and will bolt up.

WWDiesel · **Posted:** Tue Dec 30, 2025 2:19 pm

Yes, just like 03black said, it is rebuildable, but if an owner is not experienced at rebuilding and setting up rear differentials, i.e. setting up Pinion Gear depth and Backlash, you would be much better off paying someone who is very experienced in the job/process. Or getting a good complete used rear axle assembly and swapping out the whole unit. Used assembly must match year model, as 05 & 06 models are unique due to differences in ABS sensor locations and systems. Also, rear axle bearings require a special tool to remove the bearings.

The real challenge to a novice is setting up the pinion gear depth to obtain the correct gear contact pattern on the new ring & pinion gear. (heal & toe contact pattern) Without proper tools, it can take several attempts, teardowns & reassemblies, to get it perfect. But you have NO choice, it must be right!
"Close enough" simply will not work for this application.

The pinion gear depth is set by using different thickness shims between the pinion gear and the large pinion bearing. This measurement is super critical and must be 100% correct as there is no room for error. If you fail to get it right it correct, it can cause the rear end to be very noisey or worse yet, completely destroy a ring and pinion gear.

flman · **Posted:** Tue Dec 30, 2025 4:45 pm

Thanks guys, yes I heard several horror stories about a rear end rebuild gone wrong. But that still don't mean I wont consider doing it myself anyways.

As far as gears "might" be cooked, does that imply maybe it's a bearing problem only?

03black · **Posted:** Tue Dec 30, 2025 10:38 pm

No, gears being "cooked" just means that the metal have been burned and worn down/out due to not being lubricated.

You will still need to at a minimum change out all the bearings and bearing caps, set backlash, then check the gear pattern. If backlash is set correctly then the gear pattern should be correct. If. It then the gears are to worn out and you'll need to replace the ring gear and pinion.

As WW said, if you never done gears before it can be a little difficult. But the Chrysler 8.25 is really easy. If your wanting to do it yourself, watch a few videos, there are a couple of good one out there that go through the entire process. The first time I did it, it was a slow and imitating, but now I can do it with my eyes closed?

flman · **Posted:** Wed Dec 31, 2025 10:07 am

03black wrote:

No, gears being "cooked" just means that the metal have been burned and worn down/out due to not being lubricated.

You will still need to at a minimum change out all the bearings and bearing caps, set backlash, then check the gear pattern. If backlash is set correctly then the gear pattern should be correct. If. It then the gears are to worn out and you'll need to replace the ring gear and pinion.

As WW said, if you never done gears before it can be a little difficult. But the Chrysler 8.25 is really easy. If your wanting to do it yourself, watch a few videos, there are a couple of good one out there that go through the entire process. The first time I did it, it was a slow and imitating, but now I can do it with my eyes closed?

I am retired, and have plenty of time, to get it right. Not to mention it's not a daily driver, more like my ATV. I have seen the ink pattern in books a long time ago, I used to have a Motors manual, I might still have it at my old place. That book had a lot of practical knowledge, I hope I didn't toss it when I moved.

WWDiesel · **Posted:** Wed Dec 31, 2025 3:37 pm

Two tools that are a must to set up your Jeep differential,
1. A good dial indicator with either a clamp on base or good strong magnetic base.
2. The long tool for reaching into the axle tube and adjusting the carrier bearings position and bearing preload.

03black · **Posted:** Wed Dec 31, 2025 5:11 pm

Yep, made my own adjuster nut tool from a 32mm nut (I think) , a long pipe, and an old 1/2" socket. Welded all the pieces together works great.

Dial indicator with base and lots of patience adjusting the nuts. Like no more than a 1/8" to 1/2" adjustment to get the backlash just right moving from the left side to right side of the axle. (sometimes loosen the right side to tighten the left side to move the ring gear closer to the pinion gear and to get the right amount of torque specified.

The Chrysler 8.25 is in lots of Mopar products and in the jeep Cherokee so lots of advice in the off road forums. Get a crush sleeve eliminator kit unless you think you can set the to set the pinion rotating torque the first time. Rotating torque is something like 10-14 inch lbs. Pinion nut torque is like 205 foot lbs.

flman · **Posted:** Thu Jan 01, 2026 10:35 am

Okay, looking like quite the project, won't be doing it anytime soon, because I have my hands full with chores. Might check the salvage yards, and see if I can find a dry on the outside differential. Never though putting off the tranny leak, would cost me a differential.

03black · **Posted:** Thu Jan 01, 2026 1:19 pm

Just for others clarification if they come across this thread, a transmission leak would not cause a rear differential/axle problem. They are not "connected" together by fluid but rather through a mechanical connection with the drive shaft. The differential/axle problem goes bad when the rear fluid leaks out through the pinion seal and becomes so low that it cannot provide the proper lubrication to be gears and bearings. Literally a $5 seal can cause $$$ of damage if not looked at in a timely manner.

flman · **Posted:** Sat Jan 03, 2026 9:03 am

03black wrote:

Just for others clarification if they come across this thread, a transmission leak would not cause a rear differential/axle problem. They are not "connected" together by fluid but rather through a mechanical connection with the drive shaft. The differential/axle problem goes bad when the rear fluid leaks out through the pinion seal and becomes so low that it cannot provide the proper lubrication to be gears and bearings. Literally a $5 seal can cause $$$ of damage if not looked at in a timely manner.

LOL

on not Transmission leak related. But how many people that not mechanically inclined, could actually own one of these?

I knew that transmission oil smelled pretty pungent, but once I get settled at my new place, I am doing the differential, tranny leak, fuel sender not reading right, (might as well put in the Cummins lift pump type,) and now the blower motor is getting noisy. I am due for another timing belt as well, last one was in 2000, but only 15K miles ago. Gotta get a pasture built for the wife's horses, then once the weather gets nice I'll tackle the Jeep.

Rear Differential

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