Just thought I'd share my experience/method chasing down bearing and diff noise.

I came up with this after much head scratching, it's probably not a new idea but here goes anyway.

So I have a terrible diff/bearing whine. Took it to the dealership and they suggested the left rear bearing. Which I didn't believe, (I've been burned by mechanics before) so I decided to investigate further.

My issue with his suggestion was that the sound was not on one side, it was central! I pride my self on my attentive hearing you see :P

So I went about trying to find this dud bearing with the normal wheel wriggling techniques. I found that both of the rear wheels certainly had play in them. So now I'm thinking "yup it's certainly them but it's both sides".

However, after many cigarettes and staring at the rear end of the car for some time it occurred to me that the play in the wheels could be from anywhere along the axles.

GOT EM! Those mechanics wanted me to chase the darn noise around over many expensive repairs! At least I believed so anyway...

So I set up a video camera pointed at the sticker on the axle, wriggled the wheel and behold, the whole alxe moved!
I then repeated the process on the output shafts bearings, and yup, they moved too.

After all of this I felt as if I had tracked down the play in the wheels. I had, however I had missed the clue at the start to tell me it was the output shafts and MAYBE not the wheel bearings (this method doesn't rule out the wheel bearings)

This clue was that when wriggling the wheel with my hands at 12 and 6 o'clock only the top of the wheel and any real movement. This was mostly inwards movement (I have since read that mostly outwards movement can mean the same thing).

The reason for this movement is because the whole hub pivots at the bottom only. What with the design that uses the axles as the upper control arms and all, makes sense I think.

I don't by any means think that this is a catch all method but the idea certainly helped me confirm my suspicions.

Just thought I'd put this here in case anyone was stuck with a similar thing.

Also when I get these done do you think it would he worth getting the pinion bearing done too? 135000km. I dropped the diff oil (looked like the first time ever on this car) and it wasn't too bad, not completely black and almost all of what was meant to be in there was in there so I'm assuming I haven't got leaking seals and the bearings have been lubricated for their lifetime.

Cheers!
Harry

 

That's where some of us have an advantage

It might be useful to checkout the universal joints in the shafts.
One way is to grip the shafts with channel grips and move them about.

If you want to further isolate the bearings, you could undo the four nuts
at the inboard end. Watch out for the droop and make sure you keep
track of the spacer and any shims.

If you drop all three shafts, then the flanges can be rotated freely
to feel the bearings.

 

Interesting, I'll certainly give that a go!

I spoke to the mechanic again and he said that there is always a bit of inward/outward play in the top of the rear wheel on this model. Hmm ocould come some verify that for me? If that's the case I'll need to edit my initial post!

 

Glad to see someone else has noticed this. I've got the same rumble to the rear that has annoyed me for a long time. Cars got 235k and hasn't really been looked after in its time. Working through the bits has taken time. I've changed the center prop shaft bearing (knackered) Both rear hub bearings (also needed). Found what I perceived as excessive play in output shaft bearings. Replaced these with recommended bearings, but still had excessive play. Thought at first it could be shims needed adjusting as it was at least 30 to 40 thou play. Turns out the new bearings have side play??? Cured that with better quality bearings but still with a niggling groaning. I now look to the differential support bearings for the noise. Interestingly I found the easiest way to find source or location of noise was to buy several (3) button microphones and cable tie them to the hubs and the main differential. Get some one to drive the car and record each using a laptop to record.

 

Great idea! Interesting with the play in the output shaft bearings. I really want someone who REALLY knows if there is meant to be play.

The microphones is a cool Idea. Although being an audio guy that could lead me to spend much time messing with it.

So these diff support bearings, where are they?

 

Harry,

The easiest method I have found for isolating rear end bearing noise is to securely chock both sides of both front tires, then raise the rear end and set it on jack stands. Start the engine, put the transmission in Drive, and carefully probe with a mechanic's stethoscope at the wheel bearings, diff output bearings and pinion bearing, and the driveshaft center bearing. Take care not to touch any rotating parts with the stethoscope probe or any part of your body or hair. You can probe most of the bearings without actually getting under the car - just lay beside the car and reach as necessary.

A noisy bearing will be obvious. If all of the bearings sound okay, suspect:

1. The large rubber bushings that mount the rear subframe to the body. When they fail over time, they allow the subframe to come into contact with the body, allowing gear noise to be transmitted directly into the passenger compartment, or

2. U-joints.

Replacing the diff pinion bearing means a full diff rebuild. Here are photos of our XJ40 which is very similar to the X300 (same diff):

Rear Wheel Bearings
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Driveshaft Center Bearing
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Differential Output Shaft Bearings
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Differential / Independent Rear Suspension
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Welcome to Jag-lovers - Members Photo Viewing Page

Differential Rebuild
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Cheers,

Don

 

I did the one out shaft bearing ( movement 12/6 on wheel) on my '96 XJS. I just followed Yari's pictures and it worked excellent. I can't thank Yari enough.
Snowball

 

Thanks Don, a great lot of good info there!

An interesting development in the noise today, took her to the dealership and they reported back that a prior owner or even a prior mechanic did the rear wheel bearing and
neglected to put the shims back in with the proper ?pre-load? Well, anyway there was a shim missing, the bearing had come loose and damaged the shaft not beyond repair lucky enough.

I wonder how many other rear end whines could be a similar issue?

 

Ok so here's the final outcome. Picked it up from the dealership (who I didn't trust in my first post) and they reported "all good" the bearing change went well, end float set properly and the whine is all gone.

So I guess in the end my doubt was unfounded. It's hard when other mechanics have burned you in the past...

Replaced wheel bearing and the missing shim. Problem gone.

My parts guy said he does come across this a bit. He said that the set up in the hub is not very ordinary and can put a few mechanics crook. Interesting.

For all the others out there with a similar issue hopefully my experience will help!

Thanks everyone that helped out and commented!