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Old 02-06-2018, 11:51 AM
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Buzz Buzz is offline
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Join Date: Feb 2000
Location: St. Lucia, West Indies, WI
Cobra Make, Engine: Unique 427SC 383 stroker
Posts: 3,019
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Default Jag IRS pinion seal

Hi guys. I recently picked up a 3:31 Powerlock Series ll rear suspension assembly out of a '73 XJ6. It has a Salisbury 4HU case and was sitting in the shop yard fully intact in its suspension cage covered in old oil which the shop owner had poured over it to preserve it from the elements.

He offered to clean it up and pressure wash it so I could verify the axle ratio before I committed to buying it, and in the process he apparently tried to get it turning by applying a torque wrench to the pinion nut. The diff was not turning because the brakes were all gummed up and fused, so he ended up loosening and re-tightening the nut.

I knew the family who originally owned the car it came out of and verified that it was really low mileage before it was wrecked. After being cleaned up, the diff tag showed it was a 3:31 and since it all looked in pretty good shape, I got it for a very reasonable price and took it home. I figured worse case scenario is that I would have a fresh set of control arms, uprights and half shafts to rebuild my damaged old Series l 3:54 Powerlock axle.

Once I got it stripped down to the bare differential, using bolts and a crowbar on the pinion flange, I gradually rocked the pinion back and forth before turning it fully. At first, the output flanges rocked in opposite directions, leading me to the disappointing conclusion that it was an open diff, but it suddenly loosened right up and the flanges both rotated the same way as a powerlock should. Turning the output flange on one side also rotates the other side in the same direction, so I assume that it is indeed a locking diff.

My main issue is that there is a fairly steady drip from the pinion seal when I turn it, and on reading up on replacing the seal I see that because of the crush sleeve in the input shaft, great care must be taken not to loosen or tighten that pinion nut without reference marks or the bearing preload will be affected and a full diff teardown and rebuild will be needed. The diff is still full of fluid and turns smoothly and quietly in both directions with no discernible play of any kind in the pinion or output flanges.

There is no one down here with the know how to expertly rebuild a Jag differential, so the entire thing would have to be shipped out which involves a ton of paperwork, time and import/export duties, levies and taxes that I would prefer to avoid.

Is there a safe way for me to just replace the seal, clean up and re lube the differential without a full rebuild? Can a "safe range" for the pinion bearing preload be established by torque required to turn the pinion? I guess it's obvious what answer I'm hoping for.

EDIT: Just for context, once I decided to buy the axle, I went ahead and ordered a complete Team CJ Bronze bushing set and new calipers, rotors and pads, and I'm awaiting the exact shortening measurements from Alan at Unique Motorcars before I head to the machine shop to get the pieces chopped.

EDIT 2: I suppose while I have everything apart, I might as well replace the axle shaft U-Joints. Does anyone know which high quality replacement joints I should order?
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Grant me the serenity to accept the things I cannot change, the strength to change the things I can, and the wisdom to know the difference. -(wasn't me)

BEWARE OF THE DOGma!! Dogmatism bites...

Last edited by Buzz; 02-06-2018 at 12:12 PM..
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