Rear Differential Leak

Ugh! :frowning_face: I had taken Superblue to my usual tire/battery, etc. national chain shop for her annual safety inspection and, this being a different shop location than my last visit, this time they actually attempted to check the lube level in the final drive. Unfortunately, the service manager discovered that his square head drive bit was too small to engage the check plug. Another tech had one, but it was way too big (why am I reminded of The Three Bears here :open_book: ?). Anyway, he opined that the lube level was indeed low, for the simple fact that the housing had clearly been leaking – he said old lube was all over the bottom of the housing and even showed me the tops of his forearms where some of it had rubbed off onto them while he was trying to get the check plug loose. :grimacing:

I wasn’t aware that the final drive gasket has a history of leaking on our post-face-lifts, esp. @ only 85K miles (no telling how long it was going on before that). The service manager - after sitting down next to me - opined that I should look for a suspension specialty shop to take the cover off the box, r/r the gasket, put it back on and fill it up. He said it appears the only obstacle to that task is that there is some plate or frame piece that goes across, very close to the back side of the box near the bottom, which would prevent reaching the cover bolts . This would have to be removed first.

I told the tech I am worried now that the differential may freeze up at any time while going down the road, ruining things and maybe even causing me to lose control of my Jag., resulting in a crash. He told me that is indeed possible, but assured me I would hear a very disturbing sound quite some time beforehand from the back end whenever the lube level got to be THAT low. :loud_sound: He did take Superblue for a short test drive (part of the safety inspection) and said he did not hear anything that sounded like warning noise from the box. :relieved:

So, I’m thinking of parking her and driving my XJ8 again until I can get the job done, as who knows - maybe some damage has already been done to the gears in the assembly by driving it so far with lube at a lower than normal level. :question: If so, that would mean r/ring the rear axle to fix things (or have the differential gears rebuilt). :angry:

On another note, the service manager also attempted to lube the 10 lubrication points on the rear suspension (4 of which are on the U-joints) shown in the Jag maintenance schedule literature. At first, he said he could not find any, but went back for a second look after I let him know that some of them are covered by rubber blanking plugs, which have to be removed to access the nipple fittings. He came back and said he had found one or two of them, and they were on the u-joints, but when he tried to Zerk one of them up with grease the grease just squirted out the sides of the fitting, meaning that it apparently was clogged up with road debris, etc… (I guess there’s nothing that can be injected to “clean” then out?). Anyway, he said he closely examined, felt and shook the u-joints to check them to make sure they were properly intact, which they were. He advised to not worry about them then until and unless they started making noise, and then r/r them.

I thanked him for his efforts … unlike the other tech at their other shop, he seemed knowledgeable, hard-working, attentive to detail, and, most importantly, IMHO, caring about the customer’s car, almost like it were his own. :+1:

Thanks, Jerry. Yes, I was talking to a car tech bud of mine last night and he said the easiest way to “untie the Gordian Knot” when those things clog up is to just r/r them. I didn’t know that could be done. :smile:

The plug is not some mysterious size. It requires a 1/2” drive ratchet extension. If your mechanic doesn’t have one, run.

The cover might be leaking. The output shaft seals are probably leaking too. Those require dropping the rear suspension to service.

I suggest finding someone who can top off the diff, get it done, and check every 6 months. Changing the cover gasket in place is about. 2-3 hour job and might not fix the leak.

If you drive around very long low on gear lube you’re gonna be in for a big repair bill.

Regarding “finding” the zerks, why not take your ROM to the mechanic and show him where they are?


The input seal often fails resulting in oil blowing onto the bottom of the diff. Output seal failure tends to mess up the brakes.

The bottom tie plate comes off quite easily, although messy. clean it all up and I expect it will be obvious where the leak is. With that plate off removing the fill/level plug is simple.

Tru dat. The input shaft seal is relatively easy to service IF one understands how to not mess up the bearing preload and marks the nut so that it is returned to the EXACT position it was in pre-disassembly. Details are in the Book, an in various posts on this site.

Years ago, I got a box from HF. A bunch of Zerks in various sizes and configurations.

First use was on my roadster project.

Second and more extensive. got under my 83 XJ wuzza 6. found at least most of them. Some worked just fine. I used two grease guns,. One manual and one air boosted. Each an HF product. Oddly, the manual had more oomph !! Some accepted the grease others not. replaced the “stuck” ones.

However, I’d not lost my skills as a "grease monkey after school in my college years.

The diff cover? Remove the ie plate. A lot of bolts, but accessible. Why the filler is occluded? Only Jaguar interesting engineering…

tools to do the job. good jack, good jack stands. Two or more chock blocks. Creeper optional. . I seldom use mine. Just my well used "shop coat!


On the inboard brake cars, yes. I think this is an outboard brake car we’re discussing.

If that is the case I retract my “probably” leaking statement from above as I believe the seal failure is accelerated by the inboard brake temps…The output seals might be OK. Bottom line is the car needs to go on a rack, have the tie plate removed, and then you’ll know. Good news is there are a limited number of places a diff can leak.

Ah, now I see. Thanks for the pics, Bob. In other words, what is required is basically just the bare end of the 1/2" extension (correct?). Pretty clever (for once) of Jag to come up with that arrangement. Reminds me of how one can use their Jag-issued lug nut remover to r/r the oil pressure sender unit. The “nut” part of the sender is the same size and configuration as the former, as I found out once, purely on a hunch, when I got desperate to find something big enough to tighten my sender back up with many years ago on Supercat. :smile:

Yes, Superblue is a post-face-lift ('94).

So, sounds like maybe it’s just the cover plate that is leaking, after all :crossed_fingers: btw, what is “ie” short for?

Thanks, everyone … :smile:

IMHO it’s really doubtful it’s the cover leaking. We should do a poll here and ask if anyone has experienced a leaky cover. The most common leaks here are the output shaft seals and the input pinion seal. And I believe the output shafts are known leakers even on outboard brake cars, possibly because the exhaust pipes are too close.

My understanding is generally it stands for ‘for example’

Ditto !!!

and eg?


i.e. is abbreviated Latin for “id est”, which translates to “that is”

e.g. is Latin for “exempli gratia”, which translates to “for example”


What I meant was in Carl’s post:

Remove the ie plate.

Someone else mentioned the “tie plate”, so maybe this was a typo (Carl?) But then heck, I don’t even know what the “tie” plate is … Are we talking the cover on the back of the final drive box, or the thing across and near the back of it that interferes with access to removing its bolts? :confused:

I did sounder why the query regarding ie.
I think all is talking about the plate on the bottom of the diff.

Look in your parts manual and study the views of the rear suspension. You’ll see it. It’s fine to remove for access/inspection and nothing will fall out.

O.K., this is weird. I was just looking at the Classic Jag parts site to try to find the Jag part # for the differential cover seal/gasket. According to this drawing of the case parts, there IS no gasket/seal! :open_mouth:

Surely that can’t be right. If it is, then possibly the cover has just come a little loose and maybe needs re-tightening? btw, I notice some after-market kits for differential covers (e.g. Nitro) come with bolts that are “anti-vibration” type … I wonder if the Jag OEM bolts are built so. If not, possibly they did vibrate a little loose over time. :thinking:

I believe the recommended Jaguar approach is no gasket just sealant. Which can be fine IF you do it right:
Get both surfaces clean and dry. Put a bead of oil-proof sealer, like permatex black, all the way around. Put the cover on and tighten finger tight. Let it sit overnight. Then torque to spec. This allows a thin layer of sealer to set up an gives you something to crush when torquing.

(If you immediately torque the cover after applying sealant nyou’ll squeeze out most of the sealant.)

This approach will be challenging if done in place as you cannot get the cover fully out of the way, it’s trapped by the cage.

Have you figured out what is actually leaking?

Alternatively, Fel pro makes a gasket (I don’t have the PN handy but will look it up Monday) that works fine too.


Yes, was talking to a tech bud tonight and he said pretty much the same thing you did, Bob. As to Fel-Pro, frankly, I no longer trust their gaskets - I r/red my valve cover gasket with one made by them earlier this year (I posted about that adventure :roll_eyes:) and in less than 30 days it blew out again in the same spot (the back end, in the area between the pair of half-moon seals.) :rage: The major chain auto parts store I bought it at, to their credit, said if I brought the remnants of it back to them and still had my receipt they would issue me a full refund, but unfortunately I had already tossed the receipt and they had no way to confirm that I bought it there or when I bought it. :confounded: The second time around I went with Mahle for the gasket, and it is still rock solid today, several months after installation. :+1: