There is a black rubber hose that is connected to the front plate of the front diff. It's about 4 feet long and has a white cap on the end. Anybody know what it's for? I can't find it in any of the manuals.

 

vent for the differential. A small amount of pressure builds up in there, have to vent it out. The cap is supposed to prevent water from entering.

 

It's a differential breather. It's there to equalize the pressure in the axle, which changes with the temperature. If you didn't have it, the pressure that builds up inside housing could push gear oil past your pinion or axle seals.

EDIT: Also what he ^^^ said

 

thanks. I was thinking it would take me a helluva long time to refill the diff through that thing.