And the IRS is out... with pictures

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Dismantling continuum … wishbones are out as well as the output shafts.
Nice and clean, and gave the whole thing a coat of paint.

Definitely, paint the calipers. Mix or match option. Carl

And here is its sibling waiting to go back under my XJR when the weather breaks and it stops raining

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Output shaft bearings

So far so good, bearings went in fine but having trouble with the seal (JLM1264)…
First try, the seal deformed and it’s ruined.
Any special tricks that I don’t know ?

The difference of the seal OD (68.8mm) and the case diameter (67.85mm) is about 1mm, and if it doesn’t go straight in from the beginning the seal is destroyed in the process (I don’t have a press).

So I have to get new ones and I was wondering if instead I could get Viton, but can’t find the right dimensions.
Anyone has done it ?
Does it have to be the metal only case or would a normal seal work as well ? (I don’t see why not…)

What I have found so far:
CR 18626 Nitrile - single lip (1.875x2.686x0.313 inch) is a perfect match.
CR 18652 Viton - single lip (1.875x2.75x0.313 inch) OD is 69.85mm - 2.75" , so it will either have to sit at the upper part of the case as it’s bigger, or it has to be modified.

Output seals installed !
Found a big fat washer, filled it to the correct diameter, put it in the vice and it worked.

Complete with the protective shield installed.

Measuring Output Shaft’s Preload

Seal torque: 1
Total torque: 6
Bearing preload torque: 5

Pinion Seal

To remove the seal I inserted two screws and pulled it out.

New seal is in with extra sealant between the case and the seal.

Pinion cleaned, seal face polished and painted.

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why you haven’t make this work last year ???


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I think that the pinion bearings don’t have enough preload.
The diff has a very faint whine on deceleration.

Measuring drag between the backlash, on a 2mm travel area, to obtain the preload value is difficult and non conclusive to say the least.

So I have a plan:

  • Measure the pinion turning torque with the pinion nut loose (no preload). This measurement will be the total torque required to overcome the pinion seal, the output shafts and seals, and the crown bearings.

  • Tighten the pinion nut to original place and measure again. Then, subtract the first measurement and the difference will be just the pinion bearings preload, no?

  • Tighten the pinion nut until correct value is obtained.

And some questions about the preload values:
The extract from the manual that I have found states: “The torque required to turn pinion shaft should exceed by 5 to 10 (0.06 to 0.12 kgf.m.) the torque recorded in operation 3 (just the seal, no preload)”

But then it adds that “If the torque is below 25 (0.29 kgf.m.), tighten flange nut further until torque figures is between 25 and 30 (0.29 and 0.35 kgf.m.). If, however, torque required to turn pinion shaft exceeds 45 (0.52 kgf.m.), final drive overhaul, operation 51.25.19 MUST be carried out.”

It’s quite confusing…
I guess that the 25 - 30 is the combined torque for the whole diff assembly ?
It sounds like a lot of force to me.

Any suggestions welcome.

The preload torque on the pinion is for new bearings only and pinion only, not assembly. With used bearings, you need to put the nut back exactly where it was before. Overtightening used bearings will cause them to fail in short order.


Just to emphasise, Aristides…

…the described procedure was basically meant for seal replacement only. Resetting the nut to the original position ensures that not further crushing of the collapsible spacer would occur - retaining the original bearing play.

Which is measured by the torque (preload) using the backlash motion only. The backlash is indeed tiny, but using it ensures that only the resistance in the bearings (and general friction of the axle) is measured. Ie, there is no motion of the rest of the diff components - ensuring correct bearing play…

The further procedure described partly refers to actions before the nut is unscrewed. Ie, checking bearing play and adjusting as required - then mark and unscrew the bolt. But the central point is that the total torque must not exceed 45 lbs/in; it means the bearing play is too tight - and the only way to increase it is to replace the crushable…

When diff is assembled ‘from scratch’ great care is taken to get the mating between the pinion and crown wheel right. This is a separate operation - after which the pinion shaft bearing lash is set by compressing the crushable spacer by gradual nut torqueing until spec preload is reached…

The gist of this is that if nut is torqued past the original position, further crushing of the collapsible spacer may ensue - and bearing play will tighten up. Which is then noticed by the increased (beyond spec) torque required for the initial turn through the backlash…

In which case; the crushable spacer must(!) be replaced - requiring diff assembly dismantling - as indeed Dick implies

In short, if you are below 45 you should be OK…

xj6 85 Sov Europe (UK/NZ)


Pinion Seal Preload

When I unscrewed the pinion nut on disassembly I had noticed that it was nowhere near the 100 - 120 lb.ft torque specified, and therefore my inquiries for the correct preload figures, I was sure it was not within factory specs…

At the picture bellow there are two marks.

The first one, with the black line, is the original position.
This corresponded at:
50 lbs.ft torque at the nut
8 turning torque… exactly the same with the nut undone, i.e. no preload.

The second mark:
80 lbs.ft torque at the nut (not enough to compress the crush sleeve)
10 - 11 turning torque, slightly above the no preload value.

My conclusion is that the pinion nut was loose.

When originally assembled, Aristides; the nut is torqued in increments.measuring the preload each time. As nut torque is increased, the spacer starts to collapse - which influences bearing play. There is no specific torque on the nut - it is tightened until the spacer is compressed enough to give the correct preload, indicating correct bearing play.

So the initial nut torque may be anywhere, nominally up to some 130 lbsft. It is immaterial to refitting after a seal change - the nut is torqued to the mark made before it was unscrewed. In this position; the original bearing play is retained by the thickness of the collapsed spacer.

(In theory; if bearings are worn; further, very slight, nut tightening may be done to correct bearing play - but in practice; worn bearings should be replaced…)

The lash on the pinion shaft is the play between pinion and crown wheel. The shaft is moving freely, except for the friction between the shaft and in the bearings - and this is measured by the preload torque on the axle. The preload does not refer to the load/torque on the nut - but the force required to start the axle moving. It’s important that the axle is fully backed, taking up the lash, before the preload torques is measured…

The specs given for preload torque with old bearings is 20 - 25 lbs/in and with new bearings; 30 - 40 lbs/in.

Your ‘8’ and ‘11’ lbs/in is somewhat odd - and does indeed imply that the collapsible was not crushed enough initially to give the proper bearing play. That the preload torque increased with 80 lbs/ft nut torque does imply further crushing.

If your readings are correct; in theory; you should then further increase the nut torque until you reach a preload reading within the specs given. I would dearly like to know what the readings, including releasing torque on the nut before unbolting! But I see no other reason for the low reading - unless something is seriously amiss with the pinion shaft bearings. Or your measuring procedure/tools are plain wrong…

And if the preload torque exceeds 45 lbs/in; the bearing play is too tight - and the collapsible spacer must be replaced - going through the initial preload set-up. Which would be ‘inconvenient’…

The whole point of these operations is to get the bearing play correct - as measured by preload torque…

xj6 85 Sov Europe (UK/NZ)

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No it does not Frank.
I just did the output shafts, same principle, and the torque required to crush the sleeve was at least twice that.
I had to use a 3 foot bar and two hands… I guesstimate that it was around 200 lbs.ft.

I know that the seal has been changed before by a mechanic, so it’s unknown if it was done correctly.

The differential had a very faint whine on deceleration but otherwise it was very quiet, so I decided to play it safe and avoid unpleasant surprises by excessive preload on the old bearings.
When the IRS goes back and I can test drive the car, I will be able to see if what I did was good or not…!
I can always go back and re-torque.

From what I have read it’s 10 - 20 for new bearings… Please send me the document if possible.


Rear Brakes

Safety Wire

And an excellent tutorial:

The sleeves are different on the two, Aristides - the apparent longer sleeve on the pinion is likely more ‘crushable’…

But the main point is; whenever the nut is turned - it moves inwards. Which it can only do if the sleeve gets shorter - ie is crushed more.

The actual torque needed on the nut is in itself immaterial. It is the inward motion of the nut that influences the bearing play - and torque must be applied as required…

In principle; the bearing play allows slight for-and-aft movement of the pinion on the crown wheel. The whine may be induced by altering the contact points between the two due to excessive bearing play?

And, of course, if a PO was sloppy in setting the correct preload torque/bearing play - he may also have been sloppy in mating the crown wheel and pinion during assembly. Or mismatched crown wheel and pinion ‘pairing’. And, of course; wear in itself may introduce whining - as may incorrect fluid level/type in the diff.

Generally; excessive bearing play is less destructive than too tight - but it is not necessarily harmless…

Readjusting preload torque after road testing seems valid - With correct procedure and equipment; I can see no harm is setting things to specs…

I took it from the manuals description of the full diff overhaul/assembly 1985 version…

Which does not preclude that other versions may have different specs.

Generally; I’m a bit apprehensive about the friction ‘new/old’ seal and ‘new/old’ bearings isn’t more explicitly treated. But it may all be included in the spread of spec tolerances…?

xj6 85 Sov Europe (UK/NZ)


Shimming the Fulcrum to Diff gap.

Wishbones installed

Bottom Tie Plate and Brake lines installed.

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Half Shafts

U-joints replaced, cleaned and painted.
And an excellent video on how to properly replace U-joints: