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MG Midget and Sprite Technical - cleaning out a rear axle

I need to clean out the axle on a new ebay purchase as the diif has 'exploded' as the previous owner had forgotten to put any oil in the new diff!

Any recommrndations on a good product to break down the old oil and grease that is no full of diff teeth. I want to get everything spotless before the new diff goes in. I had thought about gunk, but that is horrid to use and works best when things are hot.

Should say NMC as this is my new series 3 land rover...

Mark '59 Frog

I always use petrol for jobs like that. A good strong magnet is also useful for getting all the bits out...particularly when you don't have much time between qualifying and race ;o)
Dave O'Neill2

I have found the 3 in 1 heavy duty degreaser to be pretty good. It's the one in the green can.

Malcolm Le Chevalier

David Smith

Petrol is good.

Jizer is as good.. but more expensive... but its water soluble so you can wash it all off afterwards.

C L Carter

wow, for a mess like that sounds, I would simply take it to a machine shop and have them boil it in their tank, like they do with engine blocks after machining. A system like that is designed to remove baked on grease/oil and all metal shavings as well.

Doing it at home will maybe save $50, but leave you with a lot of contaminated chemicals to dispose of somehow.

One thought on rebuilding an old rear axle housing: confirm the condition of the hub bearing threads (too low of a torque on that nut can lead to the hub/bearing squirming around, wearing the mating surface and the threads). Also check the seal surface. If there is a groove worn into the sealing surface, it can be revived with Speedy Sleeves (part # 99174).

Norm Kerr

Like David says... paraffin; petrol is too flammable.

Fill diff with paraffin; jack rear wheels off the ground; run engine for minute at 1500 rpm in 4th.

Drain diff, filter the paraffin into a cloth on a funnel into a container, and refill diff and repeat until there's no more cr*p in the paraffin when you drain.

Might take 6 or 7 goes.

Anthony Cutler

How much is paraffin these days?

Last lot I bought was in my local garage, pump your own, for much less than petrol costs. But I haven't seen any for a while and the local garage has stopped selling it.
Lawrence Slater

I like the "machine shop - get it boiled option" - best to be on the safe side, no point in putting a new diff into a grotty casing (I should know).
S G Macfarlane

White spirit (much cheaper a litre then petrol) and a little afterflush with diesel to grease things up again.
Have flushed for 3 times now(not diff but halfshafts).
They sure too make a mess when they go bust!

Arie de Best

Cheers chaps.

Had not thought of parafin, but now I think of it I havent seen it fore sale for years! Boiling is a good idea if I knew where to go and a land rover axle is a bigger beast that the Frog's. Plus everything is brand new and apart from some overheated sludge at the bottom of the diff case it is pretty clean. The halfshafts are spotless and didn't even have signs of metal shards on them.

Fortunately a mate works for a company that makes high powered magnets so I think I will try a good flush out with magnets inside the casing. Haven't had the diff out yet to see how much has broken off, but is jammed solid so I cant run it to warm it up.

Mark '59 Frog

Mark does this mean that you have given up on the heap of ferrous oxide that you had transported from the West country?

Yes Matt I manged to sell it and use the money to buy a land rover! SWMBO insisted one went before the other arrived. A nice man is turning it into a race car. So at least I will be able to see someone else use it... Just could have done with out the diff going on the way home on the LR!
Mark '59 Frog

The big DIY stores sell paraffin in 4L well as paraffin greenhouse heaters.

There is a good old fashioned hardware shop near me that sells by the litre, if you bring your own can.
Dave O'Neill2

Incidentally, What oil do people put in the rear axle? And do you use different oil to the gearbox?

I have a 79 midget and need to change my rear oil... may as well do it properly! But the manual says use a 80/140... which seems really really thick in summer? I'd have thought a 80/90 would be more sufficient.

C L Carter

C L,
you should have an Driver;s Handbook instead !

there loads and loads of thoughts on this in a recent thread EP90 GL4 to Haynes I think with fill with EP90 and top up with EP80 or other way round

I can't remember what Porter puts

then there's the utter filth of 75/90 fully synthetic
Nigel Atkins


I have the drivers handbook... I think it says 80/140 in there off the top of my head.

I can't find this thread you refer to... but then I'm rather inept and can't seem to find the archives either?

C L Carter

I wonder what Driver's Handbook your got if it says 80/140 :)

I'll look out that thread for you when I have time
Nigel Atkins

Its the Mark III Handbook... the ESSO oil is a GX 85W/140
C L Carter

ooooh, (in Bob Mortimer voice)

I've never looked that far down the table


I'll find that thread for its myriad of views

basically it's everything from if you don't use EP 90 GL4 you'll have damage through EP 80/90 sold by many MG places to the utter filth of my suggested fully synthetic 75/90
Nigel Atkins

sorry Cristian I can't find the very long thread with the long debate

basically some say EP 90 GL4 only the important point is GL4 spec didn't damage the soft bits so this must go in gearbox and axle, that GL4

the EP80/90 is GL5 which some say isn't good for the soft bits

others say the GL5 also has additives to counteract it from being bad, so they say GL5 is ok to use
it's what the MG suppliers sell you including Heritage (Duckhams)

some (on here mainly me) say not only GL5 but fully synthetic and I'll let all know when my r/axle falls apart or blows up (GL4 supporters can't wait)

Halfords sell the full range (except EP90 (GL4) I think)

the t'internet will tell you all about SAE, EP and GL
Nigel Atkins

I know what they all mean. I took a tribology course at Uni so am familiar with the various grades of oil and their additives. I'm less familiar with the midget diff and what to apply and why - you mention soft bits? are we talking gaskets seals are fibre washers?. If i'm honest I'm definitley erring on safe... which means less additives... as performace is not a main concern with me... Halfords do a castrol EP 80W/90 which is a GL4 additive level... this GL4 is american nonense anyway!
C L Carter

<soft bits? are we talking gaskets seals & fibre washers?>
no, they mean phosphor-bronze and other brassy-coloured bits
David Smith

do a quick google search on this and find a whole lot about the subject

what I learned, and posted a few months ago, here, is that when the new grades first came out, they didn't play well with the phosphor bronze parts in older designed differentials, but that was resolved back in the early '90s and is no trouble today

Norm Kerr

agreed Norm, that's my understanding too
David Smith

This thread was discussed between 19/11/2011 and 26/11/2011

MG Midget and Sprite Technical index

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