I have a 1990 XJS 5.3 convertible with 108953 miles on it. I have the drive shaft removed and noticed that I have some end play and radial play. I have not measured either with a dial indicator yet. I looked in the XJS Repair Operation Manual at the section on Final Drive beginning with Operation 51.00.00 and in the XJS Service Manual Volume 3 Final Drive Section starting with 51.00.00 looking for a discussion about how much radial play and/or end play is allowed in the pinion roller bearings before re-shimming or bearing replacement is required, but I don't see any discussion on play. The only discussion I see is about the amount of torque needed to turn the pinion by the nut.

Can anyone that has overhauled these units offer some guidance on what is normal play?

 

Basically it should be zero side to side play. The pinion is torqued quite a lot, it should be held rigidly. I suspect a bearing replacement is in your future.

The good news is that bearings are made to very precise tolerances so you should be able to reuse the shims and crush sleeves again if you are careful with your torque on assembly.

 

OR try tightening pinion nut SLIGHTLY,(like an 1/8 of a turn), turn shaft by hand,feel it!

 

Before you try tightening the pinion nut ( which I wouldn't do, because then if you do rebuild the diff you need a new crush sleeve, and getting them to crush is a very difficult thing - I couldn't do it), drain the oil and see what it looks like. If there are any metal particles in it, you have worn bearings.

My bearings were completely shot, yet the diff was still fairly quiet and had no pinion play. The oil came out with a definite metallic sparkle though. Here is what my carrier bearings looked like, my pinion bearings were in much better shape.

 

+1 on retightening to the correct turning drag. (I recall a spec for old and for new pinion seals)
it is pretty painless procedure and you have nothing to lose other than a few minutes of your time.
You make no mention of noisy diff so good chance it will work out fine.

 

It should not have any end play or side to side play, as others stated. It is possible that in the past someone replaced the pinion seal or pinion bearings and did not get it adequately tightened. You do not have much to lose by trying tightening the pinion nut to eliminate the play. Be careful not to overtighten, you cannot really measure turning torque when the differential is assembled. If you cannot eliminate the play, or if it is noisy after tightening, new bearings will be required.

 

I hadn't considered the possibility of the nut being improperly torqued after a seal change, but that's certainly a possibility. I think the spec is about 140 ft-lbs.When tightening it that much be careful of where the wheels are. If one is on the ground there is the possibility of moving the car off axle stands. Probably best to have a helper apply the brakes while you tighten the nut.

 

It is generally measured within the pinion backlash movement. Should end up with a turning torque of 25-30 lb ins.

 

Sort of. You measure the rotating torque of the pinion by itself first, then after the ring gear is installed, measure total turning torque. I suppose the OP could measure rotating torque now, then tighten the pinion nut until it increases about 10 in/lb.

 

l meant in an already assembled and fitted diff. The procedure and torque values are listed by jaguar in relation to changing out a pinion oil seal.

 

even if the nut is slightly tight but will turn by hand, when in use , temperature will warm everything up(lube oil etc) and expand it slightly!
i have done it many times, i prefer slight tight VS loose and noisy!