Hello!~It's been a while, but still having issues with the 4 wheel drive. The vacuum lines are on the axil and when in 4 high or low going up our hill to the house it sounds like some things meshing and than coming a part. Haven't taken the motor for the 4 wheel drive (axil housing on the passenger side) a part yet. I have an blue plastic vacuum line off on the passenger side by the fire wall.
It has a black rubber round disk on the end. Could this be the problem? It is the only vacuum line that no one seems to know where it goes. My 4x4 light is lighting up when putting it into 4 wheel drive. I have another 87 Jeep with the same system, but can't find that vacuum line...it's probably where it belongs. I like to keep things the way the factory set them up, so I might take the other little vacuum motor off the other axil housing and try it this weekend. Could it be as simple as a vacuum line? Thanks!~John

 

You haven't bypassed it yet? It really is a useless system, the factory only ran it for a few years before getting rid of it. Whoever thought running vacuum lines to the front axle of a 4WD vehicle was clever should go stand in the corner and be ashamed.

The mechanism in the transfer case is sufficient on its own to engage/disengage 4WD. You've already found out how much of a pain the system is!

It will fail and can leave you stranded... It's not worth it!

 

Just do this and get it over with.

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

 

I like having my front drive-line, some stuff in the T-case, and diff all free wheeling or turning 1/2 speed, the 99.5% time I'm in 2WD. The "breaking fork" was fixed by 89 I think, and a loose zip tie keeps snow or a limb from knocking the lines off the disco. They saved THEM $ by canning it, not us! Now we need to buy more, sometimes spendy parts.

 

You're dreaming. All that "feel good" stuff was a bunch of over-engineering bullcrap.

 

The truth remains. The drive-line into the t-case spins lazy, if at all. Right there the double cardigan and front U-Jiont get a break. Then there is the pinion, the T-case bearings, on down (and up), the line. Hey, if it's a "mudder" and you 4 wheel allot fine, take the extra wear. Myself, I only pull that lever back if she won't go in 2WD, then put it right back. 280K and T-case fluid and front diff looks like it's brand new. 12 years and not a single front drive-line issue. (done a # of rear U-joints)

 

"feel good" bullcrap.

Never a front driveline issue on my wife's 170K plus XJ with a NP242 and no CAD........as many more owners with a 242 can attest.

 

Ditch that crap already!! How long have you been screwing with it? Over a year?

 

Well my "new" has a 242, so now I guess I can feel good with that! PO says he had the T-case rebuilt since it was toast. 180K on it now, hope they got it right.

Btw, when I pulled the upper plug to top it off, a torrent of fluid shot out. Another issue for another day, but it seems the trans must be leaking into it.

 

Front U joints, regardless of how fast they may spin, are never actually under any load except the weight of the shaft in 2WD. This is really what matters here: power transfer. The theory is sound but I believe Chrysler discovered that, in practice, the joint will dry out before this is an issue. I got 14 years out of my '99's front joints just fine. (then I lifted it and who knows what's going on)

 

Ok!~Saturday is the day I'm going to by-pass the CAD.


So do you just plug the vacuum lines?


Do you plug them at the transfer case or at the engine?


Do you think there is any damage and what would it be to the axil or differential?


Like I said before some times the 4 wheel drive works fine.


I'm like DFlintstone and only use 4 wheel drive when I need it and then right back into 2wd.


So if your wondering why I waited so long, that was the reason...I hope I didn't do more damage.


I can't go up my hill in the winter in 2 wd, because it's not front wheel drive, but my daughters Bonneville (front wheel) goes right up the hill (packed in snow and ice).


You right Salad, I have had my 67 Dodge W200 (28 years now) and had replaced my u-joints just because of the weight on the drive line being in 2wd. I hardly ever use 4wd.


Thanks!~I printed the bypass process.


John


These Jeep are great and really fun to drive and I wonder if buying a new Cherokee instead of a RAV 4 this year would be just as good?
I'll keep the RAV it's only got 130K on it. My Jeep has 160K.

 

Just do the bypass and plug the vacuum source to the system. Kinda near the coolant bottle.

No worries.

 

I'd buy a used Cherokee myself! (preferably with a disco )

Been wondering, you see, the vacuum to the 4WD light will not pass through the disco, until the fork has actually moved over and engaged the shaft's. Pretty neat, EH? Why couldn't a guy, (after boogieing the thing up), take the vacuum that went to the "engage" port on the disco, and rout it to (the little blue vacuum switch below the bottle), so when 4WD is selected, the friggen light comes on? Or maybe I'm missing something? (other than a disco on my 242 )

Btw, a poster had a simple idea. With the fork engaged, just silicone/seal the disco ports. As long as the diaphragm doesn't leak, (never heard of one leaking, (but I bet someone has)), the air will hold it where it is.

 

Because the lever shows what range of 4wd you're in?

 

I like my CAD for one simple reason. I have an Aussie locker in the front and don't want to listen to it and or feel it when turning in day to day driving.

As others have stated, there are a few things that can fail and leave you without 4wd.

I found on mine, after lifted, the lines wanted to pull off the vacuum actuator with the slightest mouse fart anywhere near it.

I bought that cable conversion kit thing, whatever it's called and will be installing it soon.

Again, only because I have an auto locker in the front and don't want to hear / feel it when driving in 2wd.

Right now I'm sure that my driveline is spinning at vehicle speeds in the front because of the locker and have noticed zero difference in MPG or the way it drives when in 2wd.

When I put it in 4wd with the locker there's ZERO question the moment that axle engages so I know when mine is working.

If you have no locker in the front, bypassing it IMO is the easiest / best thing to do.