I just got a 1987xj pioneer and the 4×4 DOESN'T work. No vacuum going to the 4×4 motor. I've traced all my vacuum lines I believe. Only thing I think that's seems wrong is that there's a blue line that ends beneath the radiators overflow that looks like it goes to something but can't seem to find anywhere it would go? Also can a vacuum canister go bad?

 

If you have an all-time 4wd option there is no vacuum lines

 

if you remove the vacuum motor off the front axle, you can slide the collar across the split in the axle shafts, and using a hose clamp, you can tighten it around the outter shaft up against the collar, thus permanently locking it in place.
you will still have regular 2 wheel drive until you pull on the 4x4 lever. then you will have regular 4 wheel drive.

there are many other ways to achieve this, but this is the cheapest and easiest way i know of, that works. i had to do this for a couple of years with only one incident where the pressure kicked the collar off the split. but 5 minutes under neath the jeep, and i'm rockin again.

or you can go for the 300 dollar posi-lok engagement cable. i had two, but the 69 cent gear clamp worked better for me.

you might want to disconnect the vac lines and plug them somehow.

 

Or... You could suggest the writeup that I spent the time and effort to write with clear directions.. That way you dont have to worry about it "popping loose".


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

 

Both Caged and Defiance665 have working solutions, I did the 340 posilok cable with the iron shift fork, it works well. I do a lot of driving daily and wanted to be able to unlock the front axle to salvage some minute amount of fuel economy, it may not pay back the cost of the cable system but it does let me lock and unlock by choice when in 4x4 (ex tight turns). No doubt in my mind the vacuum lines become a liability. The cost of a new vac cannister, well you might as well buy the cable.

 

yeah, well... i'm lazy.

 

Ok the temp fix sounds awesome and I'm definitely gonna give it a Go
But can anyone tell me why I'm not getting vacuum?

 

either the vac motor is rusted, the diaphragm inside the vac motor is rotten, or you have a broken vac line, possibly the black ball behind the front bumper.

most common tho is the diaphragm in the vac motor.

 

Is the vacuum motor in front of the air intake? Would the vacuum motor or the diaphragm being bad effect the way the Jeep runs?

 

no, the vacuum motor is on the front axle tube. looks like this...



you might have a vacuum leak somewhere in order for it to run rough. could also be the reason you're not getting vacuum to the front axle motor. check your vac lines coming from the accumulator ball.

 

Not to be insulting but I was in understanding that that was the shift motor. And I've never seen that accumulator ball where is that located?

 

behind front bumperpass side fender well area

 

sorry, yeah, that's your vacuum shift motor.

and yup, the accumulator ball is behind the front bumper, passenger side.

as peep said, you can and should go with the posi-lok cable system with the upgraded cast fork to get rid of the vacuum system and still be able to disconnect the front passenger wheel for better 2wd fuel mileage.

cheers.

 

does this line come out of the fire wall and hang down with a smasll valve in it

 

this is the testing procedure for the axlehttp://www.4x4posi-lok.ca/pdfs/troubleshootguide.pdf