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MG Midget and Sprite Technical - Rear Axle


Looking for help. I have a 1967 MG midget 1275 that has been off the road for a couple of years. Recently had it MOT'D
and have been using it for the last couple of weeks. It has developed a grumbling noise that appears after a couple of miles. this sound seems to be coming from the rear axle. any help would be greatfully received
Stuart Atkinson

Hi Stuart

My first thought would be to check the oil level(and type) in the diff, if it it low or the wrong spec then as it warms up after a few miles it will get warmer and noisier.

A Brough

Drain and re-fill; only way to be sure what's in there.

Anthony Cutler

Ditto that. The axle takes 85/90 gear lube, up to the level of the fill port.


Gryf Ketcherside

I agree totally empty it out and refill

It may take a good while to full empty out and stop dripping, so be prepared to take your time, take a good look at what comes out

you may need a 'universal' drain plug key with its tapered arms or if you have modern drain plug then supposedly you'll need a 10mm hex (I had to file mine down to fit) or you may have a combination

spray with a good releasing fluid, leave to soak in and go and make and drink a cup tea - never rush these "dead easy jobs"

remember when replacing plugs neither go in more than a few threads (on mine at least)

Haynes says EP90

Porter EP 90 for 1098 and EPX80x/90 for 1275

and Handbook (a must for all owners) 90 for above -10 degrees and 80 for below -5 degrees

I use EPX80w/90 in my 73 Midget plus either Slick-50 or Molyslip (neither to be used in LSD of course)

I used Molyslip this time (I drain and refill at least every 3 years as it's so cheap to do 7 for 1 litre EPX80w/90 and 8 for Molyslip, I think) it quietened the whine down noticibly

You pays your money you take your choice

If grumbling noise continues then at least you've spent little money and have done a job that wont harm and would need doing sometime
N Atkins

Thanks for the information did suspect that it might be the oil. Looking under the car it looks like its the original drain plug and it looks like its going to difficult to remove it looks about 1 inch in diametre is this the normal size

Stuart Atkinson

Yes, that's the normal size. If you don't have a drain plug key, you can sometimes get away with a 3/8" drive ratchet.

Make sure you use EP90 and not just a 90 weight gear oil
Dave O'Neill 2

Replace the fill & drain plugs with hex headed variety available from plumbers merchants then you can use a socket spanner in furure. Both are threaded BSP
Alan Anstead

Stuart it wont be difficult to remove, mine only goes in a few threads, see above

Just take your time, plenty of penertrating spray (not just WD40) and patience and buy the multifit drain plug tool they're not expensive

Support the car thoroughly remain safe

Alan Anstead, Kent, United Kingdom
Replace the fill & drain plugs with hex headed variety available from plumbers merchants then you can use a socket spanner in furure. Both are threaded BSP

Doh, why didn't I think of that two weeks ago, good idea

As I said ones I got from MGOC are supposed to be 10mm hex but are not
N Atkins

Hi Folks:

Som of you may remember me . . .
I am building an Austin based single-seat racer see the picture. It is powered by a 1275 midget engine and I need your esteemed opinions on some additional power. My intention for this car is to use it in: Autocross type evens, Solo II, Gymkhanas and perhaps the odd hill climb. I will never race it wheel-to-wheel as I am too old, fat and smart for that.

My questions are: What power increase can I expect if I put a Webber on the engine? and What would be the power increase if I went with a supercharger instead?

Godspeed in Safety Fast

John Crawley


I also tried to drain my Diff, but my midget doesn't have a drain plug!?
I clearly see th filler plug but the drainplug is not there.
Are there midgets with a different type of rear-diff?.
I do have pictures.
Can anyone help?

M Veenendaal

OK - since there's a thread on it already, thought I'd widen it just a little bit ...

If you were fitting a slip dif onto a rear axle and had the chance to buy it either off or on the axle - would you take it on the axle on the grounds that you can sort whatever may be wrong with that, but at least it's already fitted and saves trying to refit to another one?

John - weber gives you higher power on faster speeds - and you lose the lower "grunt" from 2 SU carbs. As they say - you pays your money and you takes your choice ...! Please let me know what sort of events go on in Alberta ... I'm moving there next year, albeit way further north - and don't want to stop having fun!!!

Here is our tip for the drain and filler plugs

Nice to see some people arwe using our website tips :)
Robert (Bob) Midget Turbo

to answer your original question regarding the drain plug: that photo of your rear axle housing is weird, there SHOULD be a drain hole at the bottom. Apparently, your housing was either rusted, or damaged, or something in the past happened and someone welded up the hole I guess, because I have never seen a spridget rear end without a drain plug at the bottom. But it does hang down, and it is just about the lowest part of the car (aside from the exhaust)...

Anyway, that may be why your axle is making that awful noise, because it is not able to be drained and whatever is in there is gone to heck.

Here's an idea: remove one wheel, drum, and half shaft, tilt the car up as much as you can one way, and drain out a fair bit of the old oil as you can and see what it looks like. If it is just a little dark, but otherwise ok, then just put it back together and top up the axle. But if you get shiny metal shavings, or really black, yucky oil come out, then pull the differential and have a look-see. By the way, used gear oil will smell awful (sulphur), and that is natural, so don't be too thrown by a bad smell if the oil itself looks pretty good.

Or, just swap the whole darn axle assembly for a used one from a scrappie, these things last forever (usually) so there are plenty of rusted out hulks laying in scrap yards with perfectly good rear ends under them.

Norm Kerr

M Veenendaal

It would appear from your handbrake mechanism that you have a late 1500 Midget. The last 1500s - '78/79 had no drain plug in the axle. I have no idea why they changed the axle casing, but they did.

Sealed for life, maybe! ;o)
Dave O'Neill 2

Id be tempted to drill and tap a hole where its supposed to be


Ive only seen that on a chevy jimmy truck


Thanks For the tip Robert (Bob) Midget Turbo.

Prop: Good idea, however if you overshoot with drilling, you can hit the gears inside, and metal can get inside the dif during drilling and tapping.
Does anyone know the wall-thickness at the bottom of the diff, to determine the kind of screw.
And i think i will have to create a flat seal-surface.
Or else you will just seal against the threat.
M Veenendaal

the wall thickness of the housing is only about 1.5mm, so simply drilling/tapping wouldn't work real well.

But a proper machine shop (or anyone handy with welding) could drill and weld on a nut that would be plenty strong to seal against.

The last Midgets had a desirable gear ratio, and so if your car has a 3.7 rear end you definitely want to try and save that, the axle housing is not important. If you aren't ready to try and modify the one you've got, you could swap it out for an earlier one with the drain plug, and keep your diff.

Norm Kerr


Isn't the housing of the rear made from Cast Iron?
It's difficult to weld Cast Iron!
Yes I would like to spare my rear axle.
Maybe is just drain my rear diff using a tube and vacuum.
Should work i think.
M Veenendaal

cast iron? naw, it is just a big welded stamping

for cleaning it out to just change the fluid, if you remove the differential, you can reach inside and mop up any stray bits that might be floating around at the bottom. There is a sheet metal baffle (to prevent foaming), but you ought to be able to get a (clean) rag in there to soak up the remaining amount of old oil, before pouring in the fresh, new stuff.

Norm Kerr

This thread was discussed between 03/06/2010 and 23/06/2010

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