Differential seals what to do?

Hi all.
I’m slowly restoring my 1973 S1 and now the time is coming for the rear end.
New springs, bushes, shocks, discs, calipers are here.
Regarding the differential there is a big question.
Apparently no leaks 5 years ago when the car was stopped for restoration. And no leaks now on the garage floor. The diff was perfectly silent and no defects were evident on the road.
Now that I’m going to renew everything else I’m asking myself if it is wise replace the 3 seals anyway or take the risk and install as it is.
In the case, how hard is replace the seals?
Thanks all for ideas

significantly difficult, especially the output shaft seals

plenty in the archives

if the original leather seals are still in there, they will eventually start leaking

on my 420G, the output shaft seals were ok after 45yrs, but the pinion seal was leaking

its a bit of a case of shipwrights disease, as the output shaft has bearings as well,
your early XJ may have the NLA “single row ball bearing” setup

The output seals are indeed significantly difficult, the cage will have to go down and you will have to redo everything you just did to fix them if they start leaking in the near future.
IIRC, you can substitute the earlier single row ball bearing setup with the later double tapered bearings - crash sleeve and lip seal setup, in theory you could buy a new output bearing, shaft and housing assembly complete, assembled and preloaded.

The pinion seal on the other hand is very easy and doable in situ, undo the drive shaft pull the companion flange and the seal can be replaced in half an hour.

some of these seals are leather, and shrink while not in use. It is entirely possible, that once you drive the car, the seals with get re-oiled and swell up again resolving the leak. Then again maybe not.

The output shafts are a fiddlie processes. what makes it difficult is you’ll have either get the car up off the ground enough to drop the wishbones to a 90degree angle from the bottom of the car, roughly about 20 inches minimum. Carriers, springs shocks, brakes - all have to come out. Removing the rear diff subframe (and all) you’ll need about 24 inches to drag it out on top of a trolly jack. Doing the build on a bench. it’s WAY easier, unless you’re a 45 kilo contortionist with double jointed fingers the size of cocktail sticks, then do it in the car.

Now that being said, getting the IRS out of the car may prove to be a challenge. Radius arms are usually really stuck in, Then there’s the exhaust threaded through the IRS; which are either welded or rusted together. This can prove to be a determining factor. The challenge at some point will be either taking apart or getting it back in. In my case the PO welded the bits together. Both ends. (Previous Owner - F-U very much).

I’ve replaced the output shaft seals in on my Jag Mods YouTube channel This will give you an idea of what you’re up against. The lockwire video covers putting it all back together.

If you watch the video Personal Message me through this forum and I will share what’s not right in the video. I haven’t made a follow up video yet. It’s in the works.

I haven’t gotten round to the input shaft video (yet). This one isn’t too difficult. but there are a couple things to be aware of so putting it back together will be painless.

  • BE SURE to mark the nut to the relationship to the output shaft and diff housing before loosening anything. This is important because there’s a crush sleeve that sets the bearing preload * backlash for the input shaft to ring gear. This can be done by marking, with a center punch, the relationship of the nut to input shaft to housing are all in align. then when putting it all back together, everything should be as it was.
  • you’ll need a tool to keep the input shaft from turning while loosing and tightening the input shaft nut. I took a piece of flat bar steel, drill holes in it to match the driveline holes ,ran a couple bolts and nuts through & tightened, essentially making a lever to hold the flange in place. As a precaution, I also wrapped a ratchet strap around the ebrakes putting minimal pressure on the ebrake to hold everything in place through out the process. It’s best if nothing moves during this process.

So there you have it.
Hope this helps

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In theory the diff oil level is above the seals and the output shaft assembly has a small hole to allow the oil to reach the bearings.

You can just undo the small bushings at the wishbones.

The bearings pre-load setting in this video is not correct.

You mean the INPUT shaft.

Very important indeed!

Thanks for all the feedbacks and the detailed explanations I will soon need to take apart everything.

I’m thinking at this point to take the easier way and get the stub axles and the hubs overhauled by Ward Engineering (not cheap, but too dear), and skip the worst part of the troubles (I hope).

Regarding the diff pinion seal, as it can be done with the IRS installed, I will wait to see some leak before touching anything.

the Jag IRS is more or less like pealing an onion. We all start with brakes. Then as we get into it, we notice the output shaft seals have been leaking. (Which is no surprise considering there’s a huge heat source (brakes) right near a seal… )
So then we think… Ok replace the seal “How hard can it be?” My wife shakes her head when she hears me utter those words.
Well the seal replacement is easy peasy. The rest gets…, well, a bit complicated. The tools required needs more than a hammer and a set of spanners. It’s the measuring tolerances and weird ass tools for measuring such tolerances. It’s a bit intimidating.

In my case, I figured it’s already broken, I can’t break it anymore?! Well as I got into it, I quickly discovered, that YES MARK! You can break it more… So it was time to consult the lovely people of this forum as well as the myriad of Jaguar manuals to fix it. So If you are a brave chap, or in my case tight fisted with the money and missing a bit of commonsense to take on such a project, we wade through the process and eventually come out at the other end.