Outer Pinion Bearing Repair
 

Hello everybody!!!

I stopped by a Jaguar repair shop today for a diagnosis on my differential noise.

The noise started from one day to another - about 7000 miles ago.

So far, I exchanged the output-shaft bearings- without any change to the noise.

I also exchanged the fluid a few times - every time with very little shavings on the plug.

The diff has always had enough fluid, and was never leaking.

Today, the mechanics all agreed that the pinion-bearing is the culprit.

Here is the thing: I don't want to remove the differential at this time. I've been driving for quite some time already, and it doesn't seem to get any worse. So my plan was to keep driving until it completely breaks, and then just replace it with a rebuilt unit.

Until today I thought that the diff needs to come off in order to do the pinion bearing. This morning, they told me that the outer bearing can be replaced while the diff is installed.

So I might wanna give this a try.

I hope that someone can give me some input on:

#1 is it really true, that the outer bearing can be replaced while the diff is installed? and does it even make sense, just to replace just the outer bearing?

#2 do I need any special equipment or measurement tools?

#3 any other things to consider in that matter?

Ok, thanks a lot in advance for your help and support!!!

Thank you!!! Ingo

Hi Ingo,

The pinion oil seal can definitely be replaced without removing the differential, but I don't know if it's possible to do a proper job of replacing the outer bearing unless 1) you only replaced the roller bearing cone and left the cup/race in place, and 2) you didn't worry too much about getting the bearing preload within specification, which would very likely lead to rapid bearing failure. Without going into too much detail, I'll just point you to the end of photo album 3 and the beginning of photo album 4 in the first set of links below to help you understand why the preload is critical.

When replacing the oil seal alone, the position of the pinion nut is marked and then returned to exactly the same position, or very slightly tighter. But since bearings can vary in thickness by a thousandth or two, it is likely that the preload could not be returned to proper spec without measurement, and to measure the preload you have to rotate an inch-pound torque wrench through 360 degrees while watching the dial for the reading. I don't think there is any way to do that with the diff installed because the wrench will be obstructed by the underbody of the car. I suppose if you had an inch-pound torque wrench with a very short handle it might be possible, but you would have to disconnect the axles and remove the output shafts to eliminate their resistances from the measurement, then measure the preload taking into account the presence of the carrier (in the caption of one of the photos I mention how much the carrier should add to the preload measurment).

The other issue is that if the outer bearing is worn to the point of making noise, the inner bearing is worn too (though arguably less than the outer bearing).

I will be very curious to hear from any members who have replaced the outer bearing with the diff in situ, and how successful the operation was.

Here are the links to the photo albums showing our '93 XJ40, which has essentially the same GKN Salisbury open diff as many X300s:

Differential Rebuild:
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page

Differential/Independent Rear Suspension Removal:
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page


Cheers,

Don

I'm having a bad run of late with my XJS. I couple of months ago I had the rear end out and rebuilt by a suspension guy who had previously done extensive work on the front of my X300.

Even though there had been no noises from the diff, since it was out I thought it would be a good chance to do some preventative maintenance. I had him replace the output bearings and the outer pinion bearing. He seemed very confident that it would be ok to just replace the outer bearing and he wouldn't over-tighten the preload etc

Now 2 months later I've got a terrible whine from the diff and my suspension guy has closed up shop! Took it to a Diff specialist today and without even driving the car said he knew the problem was the pinion bearing because I shouldn't have replaced just the outer :(

It's booked in for next week so until then I don't know if the diff is salvageable or not. I should know with Jags, if it's not broke don't touch it!