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R180 side & rear seal replacement


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My next quest on my '72 240z was to eliminate the leaks out of the differential (rear end). So while the rear suspension was out, I dropped the entire differential, cross members, and drive shaft. The transmission must be drained before trying to pull out the drive-shaft! I'd also suggest using a floor jack under the differential as it weighs quite a bit.



Next I removed all of the pieces from the differential, including the half-shafts so that I'd have a manageable piece to work on.


I then began to work on the side seals, as that was new territory for me. After removing the half-shafts, its as simple as removing the the center bolt and pulling out the axle stub. I'd recommend working on one side at a time, rather than pulling the entire thing apart. Also, its easier if you drain the differential before you start pulling the seals out.



Keep in mind these are keyed (one side does have a flat-face)



Below is the old side-seal installed, followed by the new Beck Arnley seal which I'm replacing it with. You need to be careful when removing the old seal to not damage the mating surface. Like with replacing an oil-filter, I did smear some differential fluid on the new side seals before I inserted them.



After buttoning up both side seals, I pulled off the rear differential cover to clean the surface and replace the gasket. I did use a very very very thin layer of high-temp RTV on both sides of the new gasket.


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The diff internals look good. The pinion seal is dry and clean; nice. My advice: Dont change the pinion seal, it can be more trouble than you bargin for. Getting the preload right without doing a complete rebuild can be hard with used bearings and you end up with a whining diff.:disappoin


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Thanks for the advice, Chas....I'm in agreement not to touch the pinion seal until it starts to leak. The driver's side seal was really deteriorated, hence the reason I started to replace the rear 3.

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  • 1 year later...

Forgive me for reviving an old thread, but I am about to changes seals and gaskets while installing a Subi R180 in my 240...

What confuses me are the two plates on the side of the diff (held on with 5 bolts).

There does not seem to be a part number for a gasket there.

Should these just never be removed?

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The two plates you are referring to are bearing caps that hold the outer race of the output shaft bearings. Under the bearing caps are shims that account for the machining tolerances and apply a proper pre-load to the bearings. There is an o-ring that seals the bearing cap to the housing casting. It is not necessary to remove them unless you are changing the output bearings or unless the O-rings are leaking.

You can remove the shaft lip seals with the bearing caps in place using a seal puller you can get at Harbor Freight.

If you chose to remove the bearing caps, I would have a set of O-rings on hand and only do one side at a time to preclude mixing up the shims from one side to the other.

Edited by djwarner
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Just to add to djwarner post. You can get the o-rings from the local Subaru dealer. They only cost about $4.50ea. Its rare that they leak though because they are static gaskets and they are not exposed to any load forces like the diff cover gasket.

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