DRIVESHAFT OIL SEAL on the left losing gearbox oil

[nissias]

Hi there everyone.
We have replaced the differential with the Quaife ATB LSD unit last year, replaced the oil seals from both ends of the driveshafts, reconditioned the whole gearbox, and we still seem to have a leak of gearbox oil from the left hand side.
Has anyone faced this same problem and are there any guidelines on what to check? Is there some kind of a different seal getting between the gearbox driveshaft hole and the rubber seal that needs to go as to keep things tight there or something?
The funny thing is that this happens only on the left hand side.
Anyone have a clue what to do?
Let me know,
Nik.