About xray leaking diff unit, the problem is basically imperfect design of diff unit enclosure :

1. no gasket seal plate like in mugen seiki or like in buggy gear box.... instead, xray use a thin o-ring, which must be replace after every maintenance. Used o-ring usually will be out of place when diff cover is closed.

2. the screws that sandwich together diff cover to diff unit, they are simply too short, thus not up to the job to secure the diff cover from constant abuse of rotation. Possibly the silicone oil sip out from the cover. My friend one time lost the cover during final, he was holding 3rd position at minutes 40

3. the seal o-ring where the outdrives inserted into the diff unit, it's not up too the job either. The slicone oil easily sip out through the outdrive's shaft. I notice the oil existance near the outdrive area. I think this is the most common leaking spot.

Mugen MTX4 also have this problem too .... , mainly due to #3.