Series 3 Rover rear axle - can't undo filler plug!

Hi,

I've just started reassembling my Seres 3 after a chassis change, and I'm looking at refreshing the (Rover) rear axle as I'm fitting it...new oil seals, repacked bearings, new brakes, etc. Main incentive is having had EP90 oozing out of the wheel hub before I dismantled it.

However, I have a couple of issues.

I wanted to replace the breather. Can I check that the 'nut' I can see against the body of the axle casing is what I need to unscrew, and that the nut isn't actually part of the axle that the breather screws into? I'm pretty sure it's what I need to unscrew, and the whole vehicle has been so badly rusted that I know it's going to be difficult to undo, and likely to shear off...so I want to make sure I am undoing the right thing!

I've also hit a problem with the oil filler - I can't shift it! Any hints on how to free it up? It's the ~15mm square plug on the side that I'm trying to remove. My rear axle doesn't seem to have a drain plug, either. If I can't get the plug out, I'm thinking I may need to refill the axle through the breather hole, but any suggestion on how I can check the level? Should the level be above the half-shafts, such that it will drip out if a half-shaft is removed...or fill it until oil just starts to appear? Or is it already overfull at that point?

Any other suggestions or hints on diff maintenance, greatly appreciated!

Cheers!
Adam

Hi Adam,
Yes, the breather has a nut against the axle casing that should undo without too much force - some WD40 is always good though
There should be a drain plug, but it might be hiding in the crud under the diff... The filler plug can be tight, but it should give up if you get a close-fitting spanner and some brute force. I got one out with a Stilson and a hammer, but it made a bit of a mess of the filler plug.
From memory, the oil level should be high enough to trickle out of the axle with the hub off, but it's been a while since I had one of these axles to bits...

I would use a blowlamp and heat the plug until its very hot, then spray with pentrating oil. Have a rag handy as the pentrating oil will flash off and catch fire but what this does is the heat softens the stuck oil, the pentrating oil cools the plug suddenly so its shrinks a bit and this pulls the pentrating oil into the threads. Get a spanner on it straight away and it should move.

Diff filler plug should be filled till it flows out.
Is your plug in the rear pan or on differential.

Thanks for your replies, everyone. I've made some good progress today, thanks to your suggestions.

Got the breather off. Was actually pretty easy, as suggested, once I was confident the nut was supposed to turn and wasn't a boss, welded to the axle!

And after heating the plug (far more than I wanted to - I hate taking a blowlamp to things!, I managed to shift it. Good job I did, as the oil in it was terrible - grey and very thick. And overfull, which may explain why it was leaking out the hub. I suspect the previous owner had been deep wading with it, and the breather had let a lot of water in. So a wading kit has been ordered.

And while taking a photo to show that the drain plug on my diff was a blank with no keyway in it...I found the keyway! Absolutely full of crud, as suggested, and I just hadn't realised it was even there. So managed to get that out too, so I can properly replace the oil.

FYI, the fill plug is on the side of the main diff body, not on the back pan. It had a square lug, which I managed to get enough of a grip with, using my Irwin bolt grip remover (those are really useful little tools), as the lug had already started to get misshapen and my spanner was just slipping off.

But now I need a new plug. Are all replacements now with a square hole rather than a lug? Might be easier to get a ratchet spanner into it...

Thanks!
Adam

Pretty sure it is a bspt plumbing fitting.

The filler/level plug on the main body of diff means your diff is from a series 2 2a.

tottot said:

The filler/level plug on the main body of diff means your diff is from a series 2 2a.

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That's interesting. Both axles have the plug in the same place. I've found a few 'not original' bits on it as I've been taking it apart, but I'm surprised both axles would have been replaced. I'll keep a note of this!

Thanks,
Adam

My fillers (S2A) are on the side and have raised hex heads, a parralel thread and a flange to seal. 533358 and FRC4835

Just occured to me, perhaps the axles were changed to get higher gearing, check the diff ratios.

rob1miles said:

Just occured to me, perhaps the axles were changed to get higher gearing, check the diff ratios.

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All series diffs are the same ratio so that's a no.

tottot said:

All series diffs are the same ratio so that's a no.

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But 90/RRC 3.54 diffs fit and won't have the filler on the diff like Series diffs do

But, mine has 3.54 RR diffs in Rover axles with the brass side fillers so its possible. Could explain the swap.

Guess someone could have gone to the trouble of swapping internals to keep the filler on the diff ?

rob1miles said:

But, mine has 3.54 RR diffs in Rover axles with the brass side fillers so its possible. Could explain the swap.

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I believe very early RR's had the filler like that. Latter ones don't. I used to just pull a halfshaft and fill from the axle tube on mine.