My differential builder reached out to me today, and the rear LSD is almost ready except he was stumped by the lack of a breather / vent. There is what appears to be a breather on the differential cover, but it's sealed with what looks to be a metal plug of some sort. Looking at ebay pictures of differentials, the X350 rear differential has this vent plugged.

Does anyone know whether the rear differential of the X350 has no vent / breather? Never seen a differential without a vent.

 

I'm unfamiliar with that but all vehicles have a vent in the rear axle assembly as far as i know. when the fluid expands and contracts it would destroy the seals if it's not vented somewhere. Perhaps the service manual list it

 

That's my understanding as well, but the cover vent appears plugged at the factory. Workshop manual is silent and I'm not getting any hits searching for a 'breather' as a part.

 

The uk form has several threads on the rear rebuild/upgrade. perhaps a search on their sight. i haven't serviced mine yet to have a look around underneath.

 

To close this out, my current thinking is the plugged port on the top of the differential cover is in fact the vent and mine needs to be cleaned out.