On a 91' 4 Litre, 4x4, AX-15, XJ, what is supposed to be hooked up to the circled tube on the t-case? It is a vent tube, but does the tube connect to any other component on the jeep?

?

 

Here you go. At least I think this will help. LOL.

 

Thank you for the info. Where does the other end of the tube plug in?

 

Does not really plug in anywhere.
If you look close at the picture you will see a check valve type thing on the end of the hose.
On an XJ you will find it on the passenger side behind the engine about a foot down the tunnel.
It is kind of secured, I think, in there but really just hangs in place.
Relocated mine up to where the front diff one is in the engine compartment near the brake booster.
Got rid of the check valve and run the same breather the front diff uses.
Part number is J5352955.

https://www.rockauto.com/en/parts/mo...ase+vent,14361

 

It runs up to the firewall by the brake booster. Should have a little white cap on it too.

Edit - Ralph beat me to it!

 

Not a transfer case breather. Both that and the tranny one are about where I wrote before.
At least in my '00. I just moved both of them and the rear diff to where the front diff one is
in the engine compartment.

 

They are all atmospheric vents to allow for expansion and contraction of the air inside the cases. They are designed to be high on the body to keep water from getting in when you go wading. The white cap thingy is to keep dirt from getting it while trying to stop water. If they are blocked off, fluid will be forced out thru the seals when the cases get hot.

 

Thank you Ralph, 5-Speed, and Dave! Appreciate the details

 

@Rlmx ...

@Ralph77 gave me this info earlier that may help if you are ever rerouting or cleaning out these breather tubes:

"Top hat breather can be ordered through any Jeep dealership or bought online.
Part number J5352955.

https://www.rockauto.com/en/parts/mo...ase+vent,14361"

5/16 hose is what you want for most of the breather tubes on the XJ.