Originally Posted by bodymot

Just my thoughts on Spec-R diff, so far so good in my 09 X-Ray running 13.5 on carpet. Sanded back of bevel gears just to take moulding marks off so ran smooth, Green slime on main out put drives O-rings so helps stop leakage and on gasket to help seal ( didn’t put two gaskets on because could make satellite gears run with too much play against Bevel gears and strip). Having built real car diff’s couldn’t under stand why you would want to over fill diff, a normal car diff with a breather is only filled half way which I did with Spec-R diff. It’s sealed so any over fill will just push out of gasket or out drives when it warms up. You need air space in side so it can expand. It won’t run dry because diff gears rotate and pick up oil. I used much more 250 oil and only filled just over half way so there was air space for expansion when run. So far the only fault I can see is the washer No 9 which runs behind No 4 Bevel Gear, its really thin (0.1) and 9mm wide, could distort. Might use a thicker and wider one, Tamiya wheel spacer 0.5 x 11.5 wide would fit and make better seal on O-ring seal. If you do, don’t just file back of No 4 Bevel gears because No 8 pin will pull out drives in so you need to file out side of the case 1 & 2 were the out drives go in to case so it can run free, (don’t over do it).
It’s about 9/11 grams heavier with oil.
Is it faster? I think that’s down to how you like to drive and if you like a non slip diff. for me just a club racer, its really smooth, no slip, (so far) one less thing to worry about and its cheaper than a new X-Ray diff in the UK !
Hope this helps
Just order another one for my T3 running 10.5