Ok so I installed my rebuilt diff to the box and as soon as I try to tighten the output shaft nuts with a 1/2" socket ( not yet torqued up ) I can't even turn the output shaft by hand.
I have had the housings rebushed at the machine shop with each flange matched to the shaft with 0.001 thou clearance.
I have heard the diff fibre washers on these new rebuild kits can be too thick but I can't see this making a difference.
This setup is different to pot joint and hardy spicer.
Is it possible that the output shafts are out of square and or worn and as soon as you try doing up the nut it pushes the flange slightly into the diff housing cover and binds up.
The output flanges I guess are worn from age.
I also note that when I pulled the box apart these nuts did not seem to be tight at all and hence I was getting oil leakage from the centre of the shaft around the nut and washer.
The box is a rod change 4 syncro and the diff is 3.1 with the rebuild kit from minispares for pre A+ box.
I have attached a couple of photos for reference of the type I have.
I did remove the shimmed side to see if it would make a difference to the drivers side but there is still the same problem.
Any help with this would be appreciated.

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Did i tell you that all my minis are 850's ?

Could it be that the Bushes in the two end plates that you had machined are not truly in Line?

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DID I MENTION THAT I AM THE BEST SUPPLIER FOR MINI ELECTRICAL PARTS AND REPAIRS?
"Let us remove your "SHORTS"

good point tony, maybe i need to try an old housing to see if it is ok

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Did i tell you that all my minis are 850's ?

In My experience 0.001" clearance in not enough for those bushes and will result in the problem you are having.
As the nut is tightened it doesn't take much for the coupling to kick sideways on the spline resulting in it locking up.
Happens every time if you try to make the clearance too tight.
I normally bore the bush and try it, if it's too tight take another 0.0005" until it works.
Dave

Don't be surprised if it requires 0.003" to 0.004" clearance. Maybe More!!!

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Thanks Dave for your input
Do you use a machine ream or hand ream with a big adjustable reamer and guide ?


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Did i tell you that all my minis are 850's ?

These bushes need machining not reaming, IMO. Unless you bolt both to the diff and pilot the reamer.
I set the cover up in a 4 jaw chuck on the lathe, clock the seal recess to run true then bore to size. As David said .001" is usually not enough clearance with rubber u/j drive yokes, and Hardy Spicer joints too.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I set them up true in soft jaws (Machineable Jaws bored to suit , very accurate, almost as good as a collett) in a 3 jaw chuck and bore them in a lathe. You probably wont have soft jaws for your chuck.
4 jaw chuck or face plate set ups are also an option,

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