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MG Midget and Sprite Technical - Diff cage shims

I’m planning to rebuild my diff with a new crown wheel and pinion, this will require installing shims to align the diff cage. The traditional shims fit behind the bearings, requiring the bearing to be removed to adjust them. Spridget Mania in the states offer shims that sit on the outside of the bearing, making them much easier to adjust. The OD of the shims is 2.75”. Does anyone know of a source of these in the UK?

https://www.spridgetmania.com/part/2K7271/Differential-Bearing-Shim-010-275-Od--Sprite--midget
R.A Davis

No, but I made my own. Years ago I invested in a pack of shim steel so I can usually make whatever I need. Very useful to have. I rebuilt 2 diffs with shims on the outside, which works fine. Tricky if you need a very thin one, because it's hard to avoid crinkling it as you squeeze the bearings in. This is because you need 2 thou of pinch. I put the thicker ones of the set on the outside and that helped. I also helps to file a very slight lead on the alloy carrier and cap, which stops the shim from catching. This all applies whether you make your own or buy them.

Les
L B Rose

Les, that was my original plan, I have several tins of shimstock in both steel and brass but it's only 2.5" wide. I may give this a go as it'll only be 1/8" small on 2 opposite sides, the rest will be the full width.

Bob





R.A Davis

I will be interested to see how you get on. A project at the back of my mind is to rebuild a diff with LSD and low ratio (3.7 or 3.55).

How do you cut the shim steel? Tin snips? How do you stop the edges getting burrs?

Cheers,
Malc.
Malcolm Le Chevalier

Malc, In the past I've used tin snips on the thicker metal and a good pair of scissors on the thin stuff, it's probably not very good for the scissors but it works. I've not had an issue with burrs in the past, if the cutting tool is sharp it should minimise any issue.

I have made a batch of brass big end shims a long time ago, they were an odd shape and I needed a selection so I clamped a number of sheets between two pieces of ply and used a fretsaw.

Bob
R.A Davis

I use aircraft quality shears. On my second pair after all that bodywork! You do get a slightly tesselated edge but it compresses easily when bolted up. For a thick shim you have to drill to start cutting the inside. Do that on a hardwood block. Time consuming, but done before new shims arrive in the post (if available).

Les
L B Rose

Bob
I am using those Moss shims, bought a small range about 3 years ago. (I had them sent to a family friend in the US and they brought them over here). I searched many shim suppliers in the UK but couldn't find anything really suitable, I tried making some but the thin ones were not very good so I bit the bullet and ordered them from MOSS US, a friend visiting the UK clinched the decision for me.

The system works fine for me , but just as Les says the 002" shims always pinches when I attempt to use them. I also carefully de-burred the sharp edges on the alloy bearing housings, and similarly I used the thicker shim on the outside against the carrier not against the bearing IIRC. Other than that its a very useful setup for moving my LSD between various diff carriers/cwp.

I seem to remember they used to have 005" shims as well as the 002"/003"/010"

Its a pity that MOSS UK don't stock them they could be a steady little seller IMO.

Ian
Ian Webb 1973 GAN5

Cutting shims by hand is quite normal here, just a decent sized pair of scissors and away you go
Beer cans, jam jar lids, plenty of thickness choices
To stop thin shims crumpling ,instead of fitting the shims in the housing and then trying to fit the carrier/bearings ,fit them between the bearing and the thicker shim and slide the carrier, shims, and bearing into the housing as a unit
If you have around 6" of boiling hot water in a bucket, sit the housing in there with the pinion upwards out of the water to heat the housing,then the carrier assy will slide in easily

willy
William Revit

Willy
That's what Les and I already tried ; (with the thin shim against the bearing) but the 002" shims still crimp.....the thing is they are quite narrow as well as paper thin. I will try to remember to photo a shim this weekend)

I didn't try heating the carrier housing , I will try that next time (but I'm not needing to change the diff anytime soon , although it is due an inspection this coming winter so I might try re-shimming one of the diffs )

Ian
Ian Webb 1973 GAN5

Thread resurrection!

I am in the process of accumulating the bits for my diff rebuild. I came across these guys (link below) that seem to do bearing shims. Their 72 mm OD shims would suit shimming the outside of 7207 type differential cage bearings.

The thinnest they supply is only 0.1mm (4 thou) but hopefully it will work out OK.

https://www.thebearingcompany.co.uk/products/56mm-x-72mm-x-0-1mm-bearing-shim-washer/

You might need to copy/paste the link. Search the site for "bearing shims" for other sizes/thicknesses.

Cheers,
Malc
Malcolm

This thread was discussed between 21/07/2020 and 11/11/2020

MG Midget and Sprite Technical index

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