Bucaslaker

Not sure if I'm in the right place or not, but if you're willing to help I thank you. About a week ago I took ol' Chief, a 1991 cherokee, 4wd, off the road. At first when I put it in 4H my part time light never came on and then I shifted to 4L and it still didn't come on. So I pulled into some wet dirt and stomped it and nothing flew up from the front tires, so my 4wd wasn't engaging. However after a few more minutes my light came on and I was slinging chunks like I always have. However, today, I took off to the same spot and tried to do it again and this time it didn't engage and the part time light never came on and I got stuck and then, unlike last time, it never engaged. My 4wd won't come on anymore. Any ideas? Any detailed descriptions of how to fix this? Anyone had this problem and figured out how to fix it? Thanks guys. Yall are always the best.

Bucaslaker

Just to update, I put the shifter in 4H and got underneath to see if I cold manually turn the front drive shaft. I can't, it's locked up. So that means it's not a transfer case issue, righe? So what does that leave? How can I tell if my linkage is bad? I tried to move it around and there wasn't a significant amount of play and nothing was just hanging loose. I also have no idea where my vacuum tube are. And I'm pretty sure 91s had a vacuum system. Help please.

Constantine

My 91 doesn't have a vacuum disconnect axle.
If you have one, it will be near the passenger side control arm mounts, where they attach to the axle.
It will be obvious if it is located there, if not then you will have a smooth axle tube with no canister on it.

Constantine

Also, try having some one engage it into 4wd while you watch the linkage action from underneath.
Probably best to leave it in neutral with the parking brake on.

The original linkage has some bracketry that the linkage attaches to, it may be popped loose from one of the pivot points and not engaging whatsoever.
Should be one pivot point on the body and one on the transfercase, if I recall correctly.
I replaced my linkage system with a boostwerks engineering linkage system.... works really well.
If you don't have a vacuum disconnect axle then you won't be able to turn the driveshaft.

Bucaslaker

So if I don't have a vacuum and the linkage isn't bad but I can't turn the drive shaft, what does that mean the problem is?

cruiser54

Do you have the vacuum operated front axle disconnect?

91 was a transition year that had the vacuum setup on earlier models and then ditched the piece of crap mid-year.

If you have the vacuum disconnect, do the following and don't look back. Here's why.

CAD STINKS


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/f2/4wd...ss-91-a-38629/

cruiser54

No vacuum on the passenger side of the front axle?

Are you shifting while sitting still? That can be an issue.

Here's how the factory suggests you shift the transfer case and I've been doing this since these things were new and I worked at the dealership. Quoted from the owner's manual. The suggestions in CAPS are mine.

"To engage, shift the transfer case lever from 2H to 4H while the vehicle is moving at any legal speed". I LET OFF THE GAS, THROW THE LEVER, TAP THE GAS AND LET OFF.

4L position: " To engage, slow the vehicle to 2-3 MPH , shift the transmission to Neutral, then shift the transfer lever to the right and pull firmly rearward to 4L".

TO SHIFT OUT OF 4L, SHIFT THE TRANSMISSION INTO NEUTRAL WITH THE VEHICLE STOPPED, SHIFT THE TRANSFER CASE LEVER TO 2H, THEN THE TRANS TO D IF YOU HAVE AN AUTOMATIC, OR INTO FIRST GEAR WITH A MANUAL, AND CONTINUE ON.

Revised 11/20/2014

Bucaslaker

Would bypassing the CAD cause problems? This is my daily driver as well, which means I will be taking it to high speeds, so would the front drive shaft always being locked up cause a lot of additional wear? Or would it create a rough ride or anything? I just want to make sure it's safe and not going to break anything

cruiser54

Read Post #2. No ill effects at all.

See Post #7 for proper shifting technique.