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MG Midget and Sprite Technical - Advice on Differential please

I am attempting to overhaul my 1275 differential, and all was going ok, until I attempted to remove the pin holding the diff pin pt. no. 2A7016 in place. The pin is held in place by peening of the housing. The recommended method is to drill out the peening with an 1/8 drill, this I have done, but the pin refuses to move, even after tapping with a hammer and bending several pieces of steel rod.I don't want to do too much drilling,as the peening will have to go back on reassembly.
I don't want to leave it,as there is quite a lot of backlash on the pinion wheels.
Another problem is that new pins and housings are no longer available.
I would appreciate advice.

Dave
Dave Barrow

The offending item is 24.

Dave

Dave Barrow

IIRC a 1/8" drift should fit through the hole in the back of the housing and you give it a good hammering.

Dave O'Neill 2

Thanks for that Dave, but the hole in the casing is smaller than 1/8, nearer 1/16, its nowhere as big as the pin itself, that's why I cant get a good thump on it,

Dave
Dave Barrow

Hmmm, my memory is obviously failing me.

I do seem to remember bending a drift, and possibly even breaking one! Yes, that wouldn't be too easy if it was 1/8".
Dave O'Neill 2

I've had a quick look through the archives and it seems that the pin is actually 5/32"

In February last year they were still available from morrisminorspares.co.uk

Dave O'Neill 2

Thanks Dave, I will have a look at their site.
Dave Barrow

I just checked the diff I have on the bench and the knock out hole will just pass a 1/8" pin. I noticed that the washer next to it, under the bolt for the crown wheel, is very close but don't know if it could be positioned to partly cover the hole. I haven't measured the pin hole in the diff cage but can see the internal step and it's not big so 5/32" might be about right. The hole in the cross pin I measured at 0.179" - 0.0180" in the one I have. IIRC I removed this pin last year or the year before and left the diff cage in the final drive housing so used a long piece of 3mm rod to knock out the locking pin.
David Billington

Thanks David, the crown wheel has been unbolted, so the knock out hole is clear, but its very small, so getting a decent pin punch on it is difficult. My biggest concern is the amount of casing I am having to remove to clear out the peening.
Have done the best thing in these sort of situations, and shut the door on it, will have another try tomorrow .
Dave Barrow

here's a pic of my 1/8" pin punch; you're best to use a light hammer swung hard, rather than a heavy one which will be more likely to damage it.

David Smith

I was taught that it is easier to use a heavy hammer gently than vice-versa ;o)
Dave O'Neill 2

I was taught it's all about speed of impact and kinetic energy Dave; you need a quick impact to shock the pin into moving whereas a heavy hammer used gently will be travelling slower so won't have the same shock effect but may still carry enough energy to damage the item.
David Smith

Re the original retaining pins being out of stock.

There was a discussion about this last year, and the suggestion is to replace the pin with 'roll' pin, into which you push a 2nd thinner solid pin. -- This is what GBH the T9 g/box specialists do with the roll pins used on T9 boxes, to ensure they don't drop out.

As for removing the original. If you're defeated in your attempts, as I was, then using a suitable drift, hammer the main cross pin through. This will snap the small retaining pin, and you'll find it's remains will drop out very easily. That's exactly what I did, and there is NO damage to either the cross pin the planet/sun gears, or the casing.
Lawrence Slater

Fairly gratuitous picture. :).

Lawrence Slater

Thanks everyone, I got it out, broke a pin punch in the process, but it came out. I have some silver steel rod just a few thou. bigger than the pin, and I think I will use that on assembly, as it will be a good interference fit.
There are two flats machined on the cross pin, they don't seem to align with anything, so I assume they are oil passages .

Dave
Dave Barrow

Here is a picture of the cross pin, showing the machined flats, can someone confirm these are just oil paths, and do not have to be orientated in any way.

Tip of the month, if you want to mark something for reassembly in the same position, nick your wife,s or girlfriends nail varnish, the more lurid the better, you can wash parts and nothing will remove it.

Dave

Dave Barrow

Since the pin can only go in one way by virtue of the retaining pin, you only have 2 choices about which way round. And as the oil is splashed around equally no matter which way you put the pin in, it won't matter at all. So the choice is yours. :).
Lawrence Slater

Thanks Lawrence, I thought that was the case, but just wanted confirmation.
Dave Barrow

This thread was discussed between 10/12/2014 and 14/12/2014

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