I finally got around to fitting these parts I ordered from MS UK;
C-BTA166 DIFFERENTIAL PIN UPGRADE
DAM6624 PLANET GEAR IN DIFFERENTIAL

The information sheet that came with the pin suggests that if there is excessive play between the planet gears and pin that different gears should be sought, and that due to machining tolerances not even new gears should be fitted unchecked, or words to that effect.
My question is;
What is considered excessive play?
These are the measurements (mm) of the various parts supplied;
Pin OD; 14.26
Planet gear 1, ID; 14.42
Clearance; 0.16
Planet gear 2, ID; 14.58
Clearance; 0.32

My main concern is the 14.58 ID.
You would have to admit that a difference of 0.16mm, in machined parts is a very loose tolerance, and I would suggest that it is too far out.

Comments/experiences?

I've had that problem, and the diff didn't last long before one of the spider gears shattered. Not sure, but minisport SA might have spider gears with bushes

my solution was a 4 pin diff - it's in pieces right now and looks great

Thanks Simon,

This is the reply I got from MS UK.

Hi
I can understand your concern but the planet gears require a large running clearance to avoid failure. Original rover supplied gears actually have much more clearance. Lubrication becomes problem if it is smaller.

To which I responded;

Thanks for your response. Are you suggesting the clearance is fine? I ask because when I hold the diff by one of the output shafts (shaft is in vertical position) and spin the other it does not spin freely but catches from time to time. Having said that in the horizontal, as it will be in the car, it does not seem to catch.
I have new fibre washers in the diff and I have changed the output shafts and crown wheel. I guess I need a bit of piece of mind before I put it back in the car, not exactly the easiest part to change!
Another question, what is the ID of your bushed planet gears?

The bushed gears have ID 14.35mm

Just so people know

You will need a fair amount of clearance as the lubrication method ( if you can call it that ) is oil bath / spash, it is not like your crank where it is pressure fed.

There are a few other points to keep in mind with these gears / pins;

They don't (or shouldn't) be rotating all the time - they are very much 'short time rated',

Due to the crappy design of the diff hemisphere, at road speed above about 50 kmh, there is next to no oil in there in any event, they almost run dry. This situation is exacerbated at times of wheel spin. If the clearance is too small, they will run dry, pick up and then it's game over.

There are also very high loads on the copper thrust washers and output shafts too. There are a number of reasons why these little gears fail and I have to say, I've never seen one fair as a result of too much clearance, provided that the pin itself is not worn. Yes I have seen a very large number of failures, some even in my own vehicles (in the early days!)

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