I crawled under my 91 XJ and noticed a vaccume line comming off the top of my front diff. and it has rotted/cracked almost in two. it runs to what looks like a plastic vaccume line on the drivers side firewall....what is this line for ? and is it a vaccume line ? or is it a vent ?

Thanks

 

It's a vent for the front differential. Hit up google, I'm sure you can find a replacement somewhere for cheap

 

I believe it is a vent

 

Some Jeeps came with a vacuum disconnect on the front axle. I don't know what years had this option off the top of my head so you may not have it. You describe it coming off the top of the diff and that would be where the vent line is. The vacuum disconnect has a few vac lines going into a black pancake shaped diaphragm on the pass side axle tube.


Looks like this:

 

They stopped having this in 90

 

You mean after 90? My 90 has CAD.

 

Ok let me reword that. 90 is the last year they had that meaning 90 has it and 91 doesn't

 

91 was the last year for the vac disco.

 

Hp30 axles could have had that up untill 95. I have a 95 axle with it on it.

 

Huh! That's interesting. I know yj's had the vac disco up until 96. My front axle is from a 96 xj and its a non disco hp d30.

 

XJ's as in Jeep Cherokees stopped when chrysler took over ownership. If you have one swapped out from something else then good for you but 90 models were the last to come stock with front end dixcos.

 

I was simply talking about hp30's in general.

 

My 96 has the vent

 

They all have a vent.

 

Point is, sounds like is just the vent for the front diff. Assuming its a vacuum looking line coming off the top of the differential. Just go buy replacement line from napa, they have it in bulk, then get new hose clamps if you need to. While your replacing it, consider running the vent line near the hood, that way if you cross a deep puddle or a water crossing you wont get water in your differential.