Alloy Diff cover

Just got this , getting the parts together to replace the steel one !

That’s aftermarket I think. The late Jag ones had an extra hole for the speed sensor.


As it’s for my MK2 anything other then steel would be aftermarket !
It is made by Dana , for a Jaguar I.R.S diff ,I have blocked the breather hole up

This is the Jaguar XJS one , far too many big holes to fill for my liking , and the price they want :scream:

I’ve got that exact cover but no sport lettering

Do the fins and aluminum material really add any cooling effect? Do we have an issue with overheating diffs?

Hello Ian - noticed you stated that you have blocked the breather hole, in your replacement cover, - it has always been my understanding that the breather is there to help relieve the pressure, created by the heat build-up of the fluid, so that the fluid is not seeking a path past the axel seals - Tex.

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Absolutely right there has to be an atmospheric breather. Diffs can get smoking hot - especially limited slip when canyon carving, or even open diffs on fast interstate runs. I assumed he was referring to blocking the big openings and leaving a small bore instead. It doesn’t flow a lot of valour or oil, it just has to prevent pressure build-up, same as the small bore pipes on gearboxes. 1/4” ID is fine.

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The fins do add cooling, but with the exception of all but the very hardest of driving, like carving up a hard canyon or tracking the car, it’s unnecessary.

I think the ribbing helps to add structural strength as well,

I wonder if aftermarket 4wd Dana 44 covers fit ?

The cover is for a I.R.S diff , that’s why it has a breather hole , the MK2 Axle has a very small breather hole at the end of one of the tubes .
I made it a lot larger , and added a one way valve ,


Have no issues with the diff getting hot , I live in the UK lol
The only issue I have a a very small leak from the gasket , so that needs replacing !


The diff cover is bolted to arguably the strongest casting on the car an the ribs only stiffen the casting against rear impact. The alloy section is actually far thicker than the steel pressing and not significantly lighter.

By the time you have been rear-ended hard enough to need to reinforce a diff cover against the impact of bodywork further astern, a dinged stock cover would be the least of your worries if you survived.

As it happens, I do have a reinforced alloy diff cover from a Reliant Scimitar. The casting includes a mounting at the apex of the dome for a Watts linkage. I have fitted it to my D-Type instead of an A arm.


New Bolts and spring washers have come !
Standard size is 5/16x5/8 UNC , as the cover is thicker have gone up to 1" on the length.
2 new plugs 3/4 BSP , I will be adding Magnet’s too the plugs !

Magnets added too the two plugs !
Have made them so the Magnets work both sides , and they are removable for cleaning !

Very nice. How’d you make the bolts holding the magnets mount into the drain plugs?

I’m sure bottom drain plug would be a better place for debris catch, wouldn’t it ?
Using cylindrical (15x15mm ?) power magnet in a hollow iron bottom drain plug You could delete the bolt.
Either way - magnet’s Curie temperature is a factor here; rare earth magnets tend to loose magnetism above 60-80 deg. C.

I used a small dab of JB weld to hold the bolt in place , left it for a day , then filled the plug hollow with resin .
Yes I could have sunk the magnet into the hollow , but would have lost over 50% of the magnetic function , by using a bolt all the magnet is functional.
I have made 2 , one for bottom drain and one for the filler plug !

Had a look around for a Gasket , price was about £4.50 , about the same to post it , they do a so called uprated one , 1mm thick , but at £14 far too much to pay .
So got a sheet of 500x500 x 1mm Gasket paper for under £10 deliverd , and made my own , and loads left over for other gaskets I may need !
I used a old Gasket to use as a template , as you can see the Alloy one is a slightly diffrent shape in a few places !


I always found making my own gaskets, where possible, extremely satisfying.

I had to do for one of Margaret’s side panels, for the cooling jacket, a few years back.

And what comes next - are You using some sealant (Hermetic ?) or leaving the paper dry ?