Hi, I recently worked on my IRS (brakes, output shafts) and also installed a new pinion seal. After reassembly I ran the car for a few miles and noticed differential oil in the area under the diff. on the floor. It looked as if the leak is at one of the output shafts (which were rebuilt by a renowned place frequently referred to here).
Upon preparing the IRS for dropping it again I found diff. oil inside the joint (prop shaft flange - pinion flange). No visible leak between the pinion seal and the differential housing. Looking around I could see that diff oil was visible at the surrounding body panels. So I assume that the oil was blown back against the diff housing/brakes from there while driving.
Could I have damaged the pinion seal during installation? Any other suggestion how oil could get to that joint?
Yes. Oil can migrate along the splines where the flange is attached to the pinion shaft, if you don’t use some kind of sealant at reassembly. You might also make sure the breather above the pumpkin is clear and not blocked.
Sure, but it’s a pretty basic seal to install. I assume you used a decent seal driver to push it in square, and that the running surface on the pinion flange is not gouged or grooved? Since the flange goes in after the seal, the inner lip folding over is a less common problem than on similar lip seals, so that seems unlikely. I am not aware of pinion seal variants but I also assume you got the right seal?
Easy enough to change the pinion seal in situ. Actually easier imho since the pumpkin is held solid. Maybe pull the seal and check for damage before you go to the work to drop the irs again.
That’s a good one. Also make sure diff not overfilled. Yeah that’s page one in the book of obvious stuff, never mind how I know that. 
@Dave: Where exactly do I need to put the sealant? I did not use sealant during assembly. And how would I know that the breather is not blocked? Looked ok to me.
@Bob: Yes I got the right seal and as far as I can tell I pushed it in square. If I change the pinion seal in situ, I guess I need to remove the prop shaft, correct? Seems to be in the way…
Many thanks!
Hmm… Probably. But I wonder if you could just let it “hang” from the back of the trans so you don’t have to unbolt that
front flange? The heat shields and mufflers might be in the way, it might be more work than I realize on a stock exhaust. (My exhaust is not stock and comes of pretty easily…)
This might help…
Thanks - I will have a look at it. And thanks for the link to your thread, too.
When I replaced the pinion seal, I put the bolt back to the original position. I forgot to mark, but had a close-up photo so I could count the thread. Do you think an incorrect torque at the pinion nut could cause this leak? I do not think so, but I am obviously open for any comment. I used a seal puller to get the old seal out.
No, I don’t see how. “Incorrect” torque will show up as noise, not a pinion seal leak.
Jaguar offered a solution to the same problem with the later X-Type flange.
A small amount of silicone sealant!
XT308-01 Oil Leakage.pdf (114.3 KB)
OK that’s interesting. Sealer behind the nut, so you don’t have to pull the flange and seal the splines. I like it.
What Motorcarman said. Remove nut. Make sure the area is squeeky clean before using sealant. Tighten to where you were before. Breather is probably ok. Only way to really check it would be to remove it.
There are different pinion seals, but I think that the difference is obvious ; early is 1 7/16” and made of leather, later 1 9/16” neoprene IIRC. Is it the original differential assembly? Original companion flange? Any play in pinion bearings? That would be a sure sign that the nut is too loose.
This is very true. Fairly easy fix. Drop drive shaft, Remove nut, Flange. Verify no burrs on seal area on flange. De grease pinion splines and flange splines apply sealant ( red thread locker recommended). Around 18.14 time stamp
Red? Wouldn’t that make the flange almost impossible to remove?
Ya that’s what I thought. But this guy does a lot of trans and diffs. Maybe it’s because it’s not a piece you take apart very often. And on the occasion you do a little heat will help. Myself being a little red shy I might use blue or an anaerobic sealer.
Thanks guys! I will seal the shaft tomorrow, however, I am a bit hesitant to use red thread sealer - at this point I am not sure if I want to make this a „permanent“ connection yet. Any recommendations for blue sealer?
@Robert: As far as I know all components are original. I just purchased a new pinion seal from one of the usuals. No play in pinion bearing after tightening the nut.
Well Permatex medium strength thread locker Blue is the go to for most fasteners. Can be taken apart with a little more umf. Red has more holding strength and requires a lot of umf or some heat. Your other option is Permatex anaerobic gasket maker( 51813 ). This product dries in absence of air. So even though the splines have a couple thou clearance the nut is tight. And all your trying to do is stop hot gear oil from traveling through the splines. As long as vent is clear there really is no pressure.
Thoughts Bob?
Steph,
Not sure about US, however in UK it is a wise practise to buy 5 seals in bulk, to later on return unused 4. Believe it or not - you will need to cherry-pick the best one out of purchased lot prior to assembly. I have seen the seal’s runout of 2mm on some of these (no sht).