Bob Putnam’s explanation is very good. If I may, here’s a couple of extra hints.
I removed my entire unit from the car, because I had to rebuild the rear calipers and replace the output pinion seals at the same time. While doing all of this, I found that three of the four output shaft bearings were beginning to go bad, so I replaced all of the output shaft bearings as well. If all you are doing is replacing the pinion seal, you should be able to do that while the differential is still mounted in the car, unless your Butler has some odd frame piece in the way.
I’d highly recommend getting a Jag repair manual, if you don’t already have one. I purchased a Haynes manual; not the best in the world, but readily available at most any import parts shop and it has very good diagrams of the assembly and photos of the installation.
There are two different differential units used on the Jags, the "early" type and the "late type." The two types use different size seals on both the pinion and output shafts; so make sure you have the right size as Mr. Putnam shows in his procedure.
Pay particular attention to marking the nut and shaft prior to removing the pinion drive flange. The reason for this is that there are two opposing roller thrust bearings inside the differential which support the input pinion. These two bearings are separated by a crush sleeve, which has been crushed to the appropriate dimension during initial assembly by tightening the flange nut and checking for the appropriate drag. If you overtighten the flange nut when you reassemble, you will over-crush the sleeve. If you do that, the book says you must replace the crush sleeve, which requires disassembly of the entire unit; this is the Operation 51.25.19 that Mr. Putnam’s procedure references. You don’t want to do that if you can help it, unless you are also planning to replace the two thrust bearings as part of your repair.
Backing the pinion nut OFF is pretty easy if you have access to an air wrench and a compressor. I have an air wrench and a small 3-hp air compressor from Sears, and they worked OK for this application.
Once you have the flange removed, inspect it for any pitting or corrosion in the area where the seal rides. My unit had the old seal seated completely into the bore, which left a little bit of exposed area on the sealing surface of the flange. There was a small amount of corrosion on the unprotected surface, but we managed to clean it up OK.
I second Mr. Putnam’s advice and recommend using the Federal Mogul seals as opposed to the original Jaguar seals. The Federal Mogul seals are a double lip design while the Jaguar units are a single-lip design and won’t last nearly as long. Also, FWIW, the Haynes book recommends that you lubricate the new seal with petroleum jelly rather than grease. They claim the petroleum jelly is soluble in
oil and will result in better lubrication over the long run. I used some assembly lube that we use in similar applications on our helicopter transmissions, which is supposed to do the same thing.
When I reassembled the unit, I found that tightening up the nut to align the marks on the nut and the shaft resulted in almost no preload on the bearings. I measured the amount of drag at one of the flange bolt holes using a small spring scale, and even with new bearings and seals installed on both of the output shafts, there was almost no drag at all. From this, I figured I had to put a little more preload on the nut, which required some sort of tool to hold the flange stationary while I tightened up the flange nut. I took a piece of angle-iron, about 30 inches long, and drilled two holes in it which would match up with two of the driveshaft connecting bolt holes on the flange. I then put a couple of bolts through the holes in the angle-iron and threaded a nut on each one to hold the bolt in place. That way, I could insert the bolts through the flange holes, tighten up the flange nut a little and remove the tool to check the bearing preload. I found I had to tighten the nut about a half turn past the original mark to achieve the proper preload. If you have to do this, tighten the nut a small amount (probably no more than about 5 degrees or so) and check the preload; repeat this until you have the preload correct. If you have to do this, keep in mind that it will take quite a bit of force to tighten the flange nut, as you’re also compressing the crush sleeve at the same time. Tighten the nut incrementally, checking the preload turning torque frequently to ensure that you don’t overtighten the nut. My book says final turning torque of the flange should be 25 to 30 inch-pounds. According to Haynes, if you exceed 45 inch-pounds, you’ve overtightened the nut and over-crushed the spacer, so you don’t have a lot of wiggle room. Nice and easy should do it.
If I can help, drop me an e-mail. Hope this helps.
Jag Pinion Seal Help
Linear Mode
