88xj4.0

Im having a problem with my 88 xj 4 wheel drive. I think its vacuum related but not sure. My shift fork will not slide over to lock the axle in place. If i get under the jeep and take the plate off i can slide it over and be in 4wd no problem but it wont engage on its own. Anybody ever had this problem? Thanks

andrewmp6

Check the vacuum line to it,They are rubber and can dry rot just like anything rubber.Or you can get a pull cable kit that changes it over from vacuum to a cable http://4x4posi-lok.com/app_jeep.html

DFlintstone

The red line there attaches to the large line going to the vacuum ball with a "Y", nit far from the tranny dipstick. The valve/switch on the T-Case then directs vacuum to the Disco. I have a zip tie loosely around the disco to keep the lines from falling off, (which they do, easy!) Some people even can the thing! (it's just neat, not necessary) The early ones had a casting flaw on the fork, and the lines falling off, pissed some people off.

camohunter01

i noticed my vacuum lines are very loose on mine too. gonna check that out andrew.

freegdr

Check for vacuum to transfer case it self yet.

cruiser54

The big issue is that the CAD system only fails when you need it the most.

Kinda like when you don't realize your wiper blades need replacing until it rains....

I know somebody’s system works and he advocates keeping it stock, but my exposure to the failures is probably hundreds of times greater than his, as a result of being Service Manager at a Jeep dealership from 1980 through 1992, and being a current XJ and MJ owner.

CAD stinks. Every Jeep I work on with it, I eliminate it. Guess what I find in the process? 25 year old busted vacuum lines, bloated vacuum line connectors, bad vacuum reservoirs and piping, bad transfer case vacuum switches. In other words, had the person gotten into a sticky situation and needed 4WD, they would have been screwed!!!

That's the tip of the iceberg. The factory went through 3 revisions of the shift fork also. The fork issue is non-existent if you just slide it over and leave it.

See the link below for complete instructions. Takes less than 1/2 hour.

https://www.cherokeeforum.com/f51/fr...ss-91-a-38629/
,

freegdr

If I could find a system with a long enough cable id gladly use it. Im not to keen on the way the system is operated. But being able to disconnect the axles staying on my ride.

1976gmc20

Edit: sorry! I thought you were the original poster - not a CF veteran


The AMC XJs with the Selec-Trac (NP242 full time option) did not have the disconnect, nor do the newer versions (1991++). So I got lucky with mine and don't have to deal with this.


If Jeep gave up on the disconnect so should you


I'm not sure if any of the newer 4wds of any make have any sort of front axle disconnect ???



Seems like it was a big deal for a long time to either have lock out hubs or axle disconnect, and now it's not. I guess everybody needs all wheel drive now just to get to the grocery store


On my old Chevy, I just shimmed the (electric) disconnect with a piece of 3/4" PVC about 1 1/8" long so it is always locked together. I could spend $200 and a couple hours to put in a Posi-Lok, but then why bother ??? The only real advantage of the cable control is having the option of two wheel drive low range. I do sure wish that the transfer cases still had two sticks like they did back in the Forties


I almost never unlock the hubs on our Burban, but then it is rarely out on the highway.

freegdr

Never shoulda got rid of locking hubs.

cruiser54

I had locking hubs on my Nissan Patrol, 67 Bronco, FJ40, and Never unlocked them. LOL.

kirknd4spd

Just manually lock it, and leave it locked. Wont make any difference, except 4 wheel drive will always work. Ive done that on all my Jeeps.

freegdr

When ya snap a front u joint or axle there great to have ..No tearing stuff apart to avoid a costly tow bill.

1976gmc20

Yeah, let's see ... I had locking hubs on:
1973 K-20
1971 K-10
1980 K-10
1991 V1500 (still have since 2001)


I would unlock them for out on the highway, but having lived in the mountains or back country most of my life, it's just easier to leave them engaged most of the time and then you have "4wd on demand." Keeps everything lubricated also; I've seen "townies" come up to the mountains and their 4wd wouldn't work because they hadn't turned their hubs for a year.


My K-20 (automatic which was the reason I traded it in ) was an early 1973 and had the NP205 part time TC. Later they came out with the full time NP203 for all 4wd automatics which I thought was stupid at the time. They just had solid spline/flanges on the front instead of lockout hubs. I used to tell people that I had converted mine to "full time" by locking in the hubs Was about the same because if they got stuck they had to put it in 4H-loc and I just put mine in 4H


Now I have the Cherokee with NP242 full time option and I actually have to admit it works pretty good most of the time. Upon reflection, I think the difference is not so much that all four wheels are pulling as much as you are not pushing two front wheels with the two rear wheels. Probably even more so if the hubs are engaged (or you don't have hubs, CAD, etc) because you are turning all those shafts and gears but I think most is the rolling resistance in snow or mud.


Anyway ... it would probably take 20 years of gas savings to pay back the cost of a cable disconnect for the front axle.


I'm starting to wonder if lock out hubs were just a useless gimmick foisted on the outdoor crowd by Warn back in the 1950s ??????

camohunter01

What effect does leaving it locked, have on driving down the highway and in town? I plan on using mine for a putt around town and going to the ranch and probably needing the 4wd.

kirknd4spd

None at all. I drove mine everywhere, it was my daily driver, took it on a few out of state trips, wheeled the hell out of it on weekends. Leaving the CAD locked all the time made no difference. It drove the same, handled the same, and got exactly the same gas mileage.