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Rear Differential-replace or repair?

I heard a noise coming out from under my car (88 Jag XJ6) that sounded like 2 garbage cans jousting. I checked and noticed fluid leaking (maybe from a seal)onto the axel and wondered if I could I get by with just replacing the seal or should I change out the whole diff? The brackets and crossmembers look like they are going to be a pain either way.



Is there a chance that the diff is still good?

How do you explain the noise?

No, I’d say that the driveshaft output bearings are shot and rebuilding that diff is beyond most non dealer shops. Those bearings knock out at around the 100,000 mile mark or every 15 - 20 years regardless of what you do due to the loads imposed - even if the car is sitting still.

I rebuilt my rear end about 6 months ago, the bearings are crush sleeve pre-loaded and need to be set with a dial gauge and special tools. A time consuming task at best I had to make up a special wrench with a 6’ tube and dial indicator to accurately pull the bearings down.

A Dealer shop will cost a fortune in labor charges, you are better off sourcing a new diff and replacing the complete unit. Rebuilt diffs run at about $750.

Some shops specialize in differential work. If you are in a big market and lucky…

Jag XJ6 diffs are similar to Dana / Salisbury, unless you can find someone who specializes in these units the labor cost will far outweigh the recon unit cost - much like asking an auto electrical shop to rebuild your alternator, it’s just not cost effective.

If they specialize in these diff types they’ll likely have off the shelf recon units anyway. You can do the rebuild yourself but you need to be either fanatical or in need of getting out more. I’m still trying to work out which of those categories I fall into.

“like 2 garbage cans jousting”

I had a similar failure on my Miata (while on track). I couldn’t find a local shop to rebuild mine. I got a complete used diff and housing form a Miata dismantler for $350. It was a weekend project for sure.

To answer the questions posted by the OP, if the noise is from the diff, chances are the seal replacement option is too late. The damage has been done. Your probably better off replacing or repairing the diff, as described by the others.

However, are you sure the noise is coming from the diff? Two garbage cans joisting is a hollow banging noise. Most diff failure noise is a constant roar, as the bearings are running on chewed-up surfaces. By the time banging noises start, something is about to fall out.

First, check the diff lube. If low, add more and pay attention to how much you add. If you add about a pint or more, chances are the diff is shot or damaged. They do not like low lube levels.

Second, jack up one side at a time, grab the wheel, and start shoving it in every direction. It should not move much, and there should be no tapping or banging noises any noises leads me to believe you have worn out suspension parts causing the banging noises. If you hear or feel nothing, have a friend help, and inspect the suspension as the wheel is being shoved in and out, up and down, and forward and backward. The suspension should look tight, with no visible movements. If you see movements, the suspension bushings are worn, and need to be replaced.

Then, check the driveshafts. You do this by grabbing the shafts, and twisting them back and forth. Any wear in the joints will be apparent, and any tapping or knocking sounds means the joint needs to be replaced. If I remember correctly, Jaguar uses an independant rear axle with U-joints. All three shafts will need to be checked this way.

I’ll check…thanks.