Advice Needed on D35 Issues. Repair, Replace, or Ride it Out?

'96 XJ, 4.0L, 4WD NP231, D35, all stock, 282,000 miles

While driving at work the other day, I noticed my rear brakes smelled extremely hot for no good reason. Since it was raining the next day and I wanted to get my front tires balanced anyway, I took it to a long time friend of mine who works at a local tire and gas. Thinking the brakes were sticking or the e-brake was stuck, I asked him to check the rear brakes. Turns out they were fine but the axle seals were leaking. He put the tires back on and had me get in the XJ and start it and put it in drive while on the lift. At around 10mph with no brake you could feel a moderate shudder from the rear end. Press the brake and get shudder again around the same speed along with the driver rear brake grabbing and stopping abruptly. It didn't feel good at all and my friend acted like it was pretty bad news. He said my axle bearings were probably going bad causing the shudder.

Aside from that, I sometimes get a "Thunk" noise that I can also feel that seems to come from the center rear. It happens when I come to a stop then release the brake, then a moment after the XJ has started to roll forward I get the "thunk". It's like there is slack somewhere in the driveline and when the slack gets caught up it makes the noise. It doesn't happen every time but it worries me.

I can't seem to decide on the best way to go at this. Would it be best to pay someone to fix what I have or just replace the entire rear end? My mechanic told me it would be a five to six hour job just to fix my axle seals so I'm looking at spending some money either way. My friend at the tire shop tells me I can pick up the entire rear end for $250 at a j/y and it would be an easier fix. I don't like that idea because I wouldn't have any way of knowing if what I was buying was good or not. I tried searching for a rear end for sale online to get an idea on price. All I found was the separate parts, so I'm clueless on what a good rebuild/reman would cost.

I understand there are options to what rear end I can choose, D35 or Ford 8.8? I'd love to have a rear end with LSD but I'm unsure if that option is available to me.

I'm completely lost here, any advice would be greatly appreciated.

One more humbling question:
It embarrasses me to ask this but here goes. The stuff that is leaking out of my axle seals - is it just axle grease that can't be replaced without taking the axle apart?

First thing I'd do is smear my finger in the fluid and smell it. Chances are it is brake fluid from leaky wheel cylinders. On all my XJ's the brake wheel cylinders failed way before the axle bearings or seals failed. Except on one XJ where I left the drum full of sand and mud for weeks and the sand actually ruined my wheel bearing seals.

Brake fluid will make the shoes swell, grab and get soft. It gets worse when the the brake fluid soaked brake shoes get wet. They tend to lock up when braking because of the softening of the shoe material.

Brake fluid has a distinct smell, so does burnt oil, they aren't hard to tell apart.

Wheel bearings and seals aren't that big a deal to swap on the C clip rear differentials. The trickiest part of the job is getting the spider gear cross pin out. I've been lucky, but I've seen many people screw it up and have it turn into a pain. Sometimes the cross pin is held in there with a rolled steel pin, sometimes it is a locking bolt. A whole lot of people have snapped that locking bolt off trying to remove it. While you have the diff cover off you can inspect everything.

If you are careful you can gently open the wheel brake cylinder dust cover a little with a fine tip screw driver and see if brake fluid leaks out. If the whole dust cover pops off of the brke cylinder, you will likely have to remove the shoes to get it back on there.

I clean out my rear brakes with dish washing soap and really hot water and an assortment of scrub brushes and bottle brushes etc. I do it every year after winter to get the salt and other junk out of there and/or after mudding. If your rear seals are seeping, it builds up, the seep can be so small you can clean it up before it affects anything. Cleaning it up and periodic inspection is the only way to tell if the seep is major or minor. I've found really hot, almost boiling, water and soap to work better than brake cleaner on brake fluid. Brake cleaner works better on gear oil.

8Mud said:

First thing I'd do is smear my finger in the fluid and smell it. Chances are it is brake fluid from leaky wheel cylinders. On all my XJ's the brake wheel cylinders failed way before the axle bearings or seals failed. Except on one XJ where I left the drum full of sand and mud for weeks and the sand actually ruined my wheel bearing seals.

Brake fluid will make the shoes swell, grab and get soft. It gets worse when the the brake fluid soaked brake shoes get wet. They tend to lock up when braking because of the softening of the shoe material.

Brake fluid has a distinct smell, so does burnt oil, they aren't hard to tell apart.

Wheel bearings and seals aren't that big a deal to swap on the C clip rear differentials. The trickiest part of the job is getting the spider gear cross pin out. I've been lucky, but I've seen many people screw it up and have it turn into a pain. Sometimes the cross pin is held in there with a rolled steel pin, sometimes it is a locking bolt. A whole lot of people have snapped that locking bolt off trying to remove it. While you have the diff cover off you can inspect everything.

If you are careful you can gently open the wheel brake cylinder dust cover a little with a fine tip screw driver and see if brake fluid leaks out. If the whole dust cover pops off of the brke cylinder, you will likely have to remove the shoes to get it back on there.

I clean out my rear brakes with dish washing soap and really hot water and an assortment of scrub brushes and bottle brushes etc. I do it every year after winter to get the salt and other junk out of there and/or after mudding. If your rear seals are seeping, it builds up, the seep can be so small you can clean it up before it affects anything. Cleaning it up and periodic inspection is the only way to tell if the seep is major or minor. I've found really hot, almost boiling, water and soap to work better than brake cleaner on brake fluid. Brake cleaner works better on gear oil.

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My passenger rear wheel cylinder was replaced recently. I noticed one day that the inside of my tire was unusually clean looking and it turned out to be brake fluid. I never got this odor from the brake fluid at all. When my friend removed the drum on the driver rear side I expected to see the same black, rotten, rusted self adjustment cable that I found on the passenger side but it looked new. I have no clue if the driver side wheel cylinder got replaced or not but the self adjustment cable obviously had. I'm pretty sure it wasn't brake fluid either way because the axle seals were leaking on both sides and as mentioned, at least one of my wheel cylinders is new.

I won't be attempting to repair this myself. The XJ is my work vehicle. I get one day off at a time usually, and I don't have time to be farting around with it. I often wish I had the opportunity to take the time to learn and do things myself. It's not easy when you only have one vehicle though.

We were snowed in here with around twenty inches of snow over the course of two weeks. My old work horse got put to the test a few times and performed well but revealed some weakness from age. Good thing it's tax return season. :clap:

Gear lube can also cause brake shoes to swell, grab, shudder and of course smell bad when they heat up. I always replace wheel cylinders in pairs. Axle seals should not take 5-6 hours to replace. I rebuild Chry 8.25 and d35 axles in that time. I work at a gear shop in Clearwater, Fl. You should be able to pop out the rubber fill plug in the inspection cover to check gear lube level. As for your "thunk" the cheapest thing to inspect would be to remove the driveshaft and grease the splines of the slip yoke. The splines sometimes get wear in certain areas, especially with high mileage vehicles like yours.

93blackxj said:

Gear lube can also cause brake shoes to swell, grab, shudder and of course smell bad when they heat up. I always replace wheel cylinders in pairs. Axle seals should not take 5-6 hours to replace. I rebuild Chry 8.25 and d35 axles in that time. I work at a gear shop in Clearwater, Fl. You should be able to pop out the rubber fill plug in the inspection cover to check gear lube level. As for your "thunk" the cheapest thing to inspect would be to remove the driveshaft and grease the splines of the slip yoke. The splines sometimes get wear in certain areas, especially with high mileage vehicles like yours.

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Thank you!

I may have been over reacting a bit. I had the odor from my rear brakes for three days. I drove quite a bit at work today and didn't notice any odor. My axle seal may be seeping as 8mud suggested and I will keep an eye on it. I've had it in some deep snow and exposed it to a lot of road salt in the past two weeks so maybe that had something to do with it.

I'll keep an eye on my differential fluid level as well and look into greasing the slip yoke splines. I'll also shop around before I have the seals replaced. Again, thanks!

The axle bearings and seals are not a big deal. Pretty easy to replace.

The shudder you are experiencing after stopping sounds like the rear drive shaft is binding. I would pull it out of the transfer case, lube the splines and reinsert. That is provided you have the stock drive shaft.

Talyn said:

The shudder you are experiencing after stopping sounds like the rear drive shaft is binding. I would pull it out of the transfer case, lube the splines and reinsert. That is provided you have the stock drive shaft.

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I've read several people report that lubing the transfer case slip yoke (what he's describing above) cures that clunk. I've had the same clunk in mine for probably 100,000 miles. Once of these days I'll get around to fixing it.

do you have ABS?

if not, find a later model 8.25 and it's driveshaft in the yard.
swap it.
be happy with a new much stronger axle with less mileage for $150.

You can find a 29-spline 8.25 all over the place. Swap is really easy, just need to unhook the parking brake cables from your D35 and move them over. New u-bolts for the larger tubing. Takes an afternoon.