Rear differential breather valve operation

[OilUzer]

I am told that my truck has a one-way rear diff breather valve. It only breaths out when it gets hot (air/fluid expansion) in order to vent the pressure buildup. The valve is supposedly one way so theoretically if it goes under very deep water, it won't suck in the water ... That's not a concern for me (for example valve failure) as I never go that deep.

Q:
assuming that it is a truly one-way valve, how does it works after it cools off? Is it in vacuum or will it suck air from the gasket?

 

[ka9mnx]

All diff breathers use a one way valve. It's to keep out dirt not water. It isn't a complete seal so when the diff cools down air leaks back in.

 

[OilUzer]

All diff breathers use a one way valve. It's to keep out dirt not water. It isn't a complete seal so when the diff cools down air leaks back in.

the valve location is on top of the rear diff. Not low but not super high either. Theoretically speaking, can the water get in if you cross very deep water when rear diff is hot? Can the valve block water but not air?

 

[Lyman]

Duplicate post

 

[Lyman]

If you are doing any water crossing you should have a hose on your Diff vent. The other end mounted as high as possible. Always do a fluid change if it was submerged.

 

[ka9mnx]

the valve location is on top of the rear diff. Not low but not super high either. Theoretically speaking, can the water get in if you cross very deep water when rear diff is hot? Can the valve block water but not air?

Your manual should state to change the diff fluid as soon as possible after crossing deep water.

 

[wings&wheels]

Various folks sell remote vents that connect a hose to the vent port that you then route somewhere high. Back in the day Toyota, and maybe others, had a sealed system with a plastic bellows that expanded and contracted w/ the diff temp. I always thought that was clever.

Funny, I just pulled apart a rear diff vent from my old Rover. It was so cruddy after 39 years that I couldn't really free it with brake cleaner so I replaced it, cleaning them is a service item. It is a brass ball that sits on the piece that threads into the diff and the whole device is covered by a brass cover vented at the base. No sealing seat so, as mentioned, the seal is good enough to keep water out but will allow air in as the diff cools.