Originally Posted by Mandirigma

I had the same issue with the spec r diff. I had it for a few months. Teeth of the gears lost their edge and would slip. I did notice a bit of leakage of the diff oil but didnt think it was enough to cause the diff to completely strip the internal gears of the diff. Ive resorted to using the standard ball diff until AE final release their own gear diff.

Originally Posted by Martin Hofer

Hello there.

Here is my Experience with the Spec R Diff. Having only used the
yokomo diff before my initial mistake was to try and make it smooth
right out of the box by sanding the gears.

I found the gears to break if you do more than just slightly polish
them.

So mistake 1: do not sand down the gears, just polish!

As for the supplied shims:

Theres a small 1/10 shim and a larger 2/10 shim supplied. The 1/10
shim is the old one and will break if you run it in modified!

Grease on the oring:

I used Xenon Shock grease (pink one) on the X ring and so far the diff
is surprisingly well sealed. With a gear diff there will always be
leakage but atleast it leaks less than the yokomo diff :-)

Which and how much oil to use:

I have tested 100wt and 50wt to get a Feeling for how the diff reacts
to varying oil thickness. 100wt felt easy on turn in but was a bit loose
on accelerating as long as traction was low. 50wt oil was easier on
power with a bit more turn-in.

Fill the gear diff with only the main gear installed up until the oil is
approx .5mm below the bottom of the centergear guiding slots (hard to
explain :-) ). If you push the centre gears in the oil will use through it.
If there is no oil in middle of the cross holding the centre gears you
have not filled the diff enough. The cross centre shall jut be covered
with oil.

Again note that the diff will not be smooth right away but needs one
run to break-in the gears.

Also note that you might need to loosen the rear belt tension by one
notch.