where does this black hose go?

[jdstrickland]

Diffs and t-cases are vented. The trans is vented as well. Typically, the trans will have a check valve that lets air blow out, but closes to prevent water from getting in. The diff and the t-case may or may not have a check valve, but if they do not then they should vent above the high water line, which should be lower than the throttle body.

You can follow the vent hose to the component that it is venting, if you really want to know what a hose is for.

[ants_oz]

Originally Posted by Jungerishere

So which is correct? Trans or diff vent tube? I do not know of any type of diff that require venting...?

Most EVERY type of diff requires venting, otherwise as soon as it heats up with use, it would become a pressure vessel and most likely, blow either an input or and output seal.

Even little old X5's are fancy enough to have ventilation on both the front AND rear diffs! Isn't that amazing don't you think?!

[chivas]

Originally Posted by ants_oz

Most EVERY type of diff requires venting, otherwise as soon as it heats up with use, it would become a pressure vessel and most likely, blow either an input or and output seal.

Even little old X5's are fancy enough to have ventilation on both the front AND rear diffs! Isn't that amazing don't you think?!

so it's a diff vent?

[ants_oz]

Seems so to me, based on the diagrams. Which, by the way are available on realoem should you want to look yourself... Same place, you can find a diagram of the trans vent which is in a completely different area on the vehicle