my XJ.... an insult to Jeep

'90 XJ 4.0, AX-15, 231, vacuum disconnect front dana 30

my 4wd will not work!

i was destroyed last night by a nissan FWD car in the snow, i couldn't even move

so i have been having this problem for a while, here is all the info i think may be useful

-part time light goes on( so this section of vacuum works)

-"feels" like it's in 4x4, 4-lo operates at the speed it should, steers like it's in 4

- front driveshaft spins when engaged, yet neither tire in front spins

-clicking noise when 4 is engaged( hi or lo) and no front wheel spin on slick surface

dealer says it's fine(i know, i know)

maybe a shift fork prob??, how do i know?

please help i need some advice to remedy this problem and stop embarrising the Jeep name!!!

Check the vacumn lines to the front shift fork, otherwise this sounds like a shift fork problem.

i have checked the lines to the best of my ability, them seem alright, so assumeing these lines are okay, the shift fork is my culprit?, how do i go about checking this out and replacing it? am i on the right track or could it be some other unforseen problem?

If you have a Haynes manual, I believe they have a system for checking that vaccume accuator. I had the same problem in my YJ, 4wd light was on, and on jackstands all four wheels would spin, but with little effort you could hold both front wheels. If I remeber right, I had to hook up a vaccume gauge to the input line and check the accuator that way to be sure. In my case even under vaccume the accuator did not work, replaced it and everything worked fine. Of course you might still have TC problems but this is an eaiser thing to test IMO. Good luck

Pull the shift fork housing, check the fork for cracks.

Rev

Put in a Posi-Lock so you can manually engage the disconect. It's easy to do, and there are even write ups to build it yourself if you do not want to spend the $100. Then find that Nissan and tear him up!

Mine did the same thing, feels like 4 lo, but really no front wheel spin. I got rid of all that junk and went to a manual disconnect with a cable... its not that hard, but takes some tweaking to get it just right... good luck

if the fork is in good shape there's an easy enough way to bypass the vacuum motor until you can repair or replace it.
Pull CAD vacuum motor, slide the engaging collar to engaged.
Put the fork on backwards, it will hold it engaged.
Your front DS will spin all the time, just like you had a solid axle.

so i got under and had a good look at all the lines....all are good , so i'm going to pull the fork and take a look( and i belive replace it) my first question is about the gasket, i assume there is one, will it need to bereplaced or can i get away with reusing it?, my second question is if there is a company that makes a heavy duty shift fork, i have looked into the posi-lock system and have heard good things so i think this is the route i will got down

nice tip 87manche

Reuse.

and the heavy duty fork is made by Jeep.

Steel fork from dealer.

Rev

okay ,so i got under and pulled the housing to my suprise the fork is not broken or cracked but there is play i would say roughly 2-3mm of it from side to side should there be any play in this fork? if not , ill replace the whole unit and there will be no further questions.

thanks !