I felt something was amiss with my diff in September but simply haven`t had the time to remove the gearbox for inspection . Upon stripping it was clear the the issue wasn`t worn clutch plate, but a complete failure of the inner clutch drive tabs. This is a real shame, the diff performed really well but even with my sympathetic driving and mapping it simply couldn`t handle the power and grip I was trying to put through it.
After a lot of research I settled on a Gripper plate diff as a replacement. Their clutch plates have 14 internal teeth per clutch instead of the Kaaz`s 6. This should be significantly stronger.
Spoke to John @ Gripper and settled on their Track/Race ramp angles and preload.
Bought a new pair of SKF bearings at the same time.
Looking back and I should have fitted the ringgear first. It would reduce the chances of damaging the bearing. As it was I didn`t but if you are doing it, fit the bearings last.
First job was to fit the speedo drive, this is a simple push on plastic gear.
It slides onto the diff and can be pushed on by hand.
Bearings are SKF BT1B 328612 C/QCL7C`s
Bearing in position
To press the bearing on I found a steel disc that is the same diameter as the inner race, that allowed me to press it on most of the way.
Once the top of the bearing is flush with the diff casing, you can see it needs another 1mm or so to be fully fitted.
I used an old inner race on push the bearing the rest of the way
Fully in place
Repeat on the other end
New bearings fitted
Next were the ARP ringear bolts.
The splines grip into the diff casing to stop them spinning when tightening the bolts.
Start the bolt by hand
On the press, I supported the underside of the diff with some old threaded fittings
I found something the same size as the stud head to press it in
Pressed in place
All studs fitted and ready for the ringgear. I find it easier to set preload without the ringear as its a bit easier to lift the diff in and out, but it really doesn`t matter
Setting the preload
Remove the old bearing outer race.
Once removed it`s clear to see the shim
now refit the new bearing outer races with no shims into each side of the gearbox casing
Fit the diff
Bolt the 2 halves together as usual. I drilled a plate to fit the bolts through to give me a base for my Magnetic dial gauge.
Set the gauge pressing on the bearing. lower the end so the gauge is already reading at least 1mm. This is the gauge `preload`, which ensures any extra movement of the bearing is registered. Otherwise, if the gauge isn`t already reading, you could miss a part of the movement then zero the gauge
Support the gearbox casing off the bench and reach underneath, lift the diff by pushing on the bottom bearing
Note how much the diff lifts on the gauge
in my case is was 0.022″ Convert to mm and that`s 0.5588mm
For my 02S gearbox, the diff preload is :
Measured value (0.5588mm)
+ Preload for 02S (0.25mm)
Shim required = 0.5588+0.25 = 8088mm
You can also get the value from this table.
I had several shims from previous gearboxes I’ve stripped. Most are 1mm but I had a 0.8mm one ! Lucky or what. Otherwise I`d have had to order one from VW.
On the VW Gearboxes, the shim always goes on the upper housing side. The design of the crownwheel and pinion always has no shim in the bellhousing half.
Remove the bearing race then refit with the shim.
Here is the race almost fully pressed in.
Fitting the ringgear onto the diff
I tapped it on with a soft hammer
The bolt torque settings can be found with the bolts, but if lost get them from the ARP website
In my case they are 204-3002 which are 45 ft-lbs
Fortunately if just fell at the end of the small torque wrench range.
Apply supplied ARP lube to the threads AND the mating face
Held in softjaws and torqued up in stages and working in a criss-cross pattern to ensure they are pulled up square
Once diff with new bearings, preload set and ringear fitted 
Next is to reassemble the gearbox, refit into the Golf and bed in the diff with some clockwise and anticlockwise circles in an empty carpark at low speeds then switch to figure of 8`s to ensure a nice steady bedding in. This isn`t critical but it is recommended.