couple recent issues with my newly acquired 90 Beater

first and foremost its a 90 Cherokee 2 door 4x4. 4.0, AX15 (i think) 231 30/35.

Got it out on the road tonight, put her in 4hi and as im driving I feel a "pop". My Fiancée looks at me and says "what was that" to which I reply, "no idea". I continue on our trek to a small side lot and pull in, put it in 4lo. Does the same thing. Doesnt really feel like its disengaging, but hell it could be. Also, the "part-time" light on the dash would periodically go out. usually when I'd let off the gas. It does not do it in 2hi. Any idea what could be causing this and what I should check?

Once home, I shifted to 4lo in 1st gear and crawled around the yard. Popping persists and I start to smell a strange yet familiar smell. If you recall toy trains that emitted smoke had a noticeable smell, that is the smell I was smelling. Not sure if I was seeing exhaust smoke or actual smoke though... Any idea what could be causing this and what I should check?

Any help would be appreciated!

Sounds to me like you may have vacuum issues and the D30 CAD axle is engaging poorly or disengaging on you.

You need to inspect the vacuum reservoir--OEM its located under the front bumper, passenger side. It is either a shaped like a ball or a capsule with one or two vacuum lines attached. The hard vacuum line likes to break around the battery, so check there.

There is vacuum to a switch on the transfer case, and two lines that run from the transfer case to the D30 CAD vacuum motor--engage and disengage. There is a vacuum line off the D30 CAD vacuum motor that runs up to the passenger side firewall where the vacuum activates an electrical switch to operate the 4x4 light in the IP.

Here is a JP Magazine article on the D30 CAD and some options: http://www.jpmagazine.com/techartic...154_0904_dana_30_vacume_disconnect/index.html

Here is the full test from the FSM for the D30 CAD:

Raise and support the vehicle. Disconnect the vacuum harness from the axle shift motor and connect a vacuum pump to the vacuum shift motor front port.

Apply 15 in. Hg of vacuum to the front port and rotate the right front wheel to fully disengage the outer and intermediate axle shafts (i.e., shift to two-wheel drive operation).

The shift motor should maintain the vacuum applied to the front port for a minimum of 30 seconds. If the motor does not maintain the vacuum, replace it. If the motor maintains the vacuum proceed to the next step.

Disconnect the vacuum pump from the vacuum shift motor front port. Connect the vacuum pump to the vacuum shift motor rear port, cap the port for the indicator lamp switch, and apply 15 in. Hg of vacuum to the rear port.

The shift motor should maintain the vacuum applied to the rear port for a minimum of 30 seconds. If the shift motor does not maintain the vacuum, replace it. It the motor does maintain the vacuum proceed to the next step.

Remove the cap from the port for the indicator lamp switch and determine if vacuum was present at this port. If vacuum was present, the shift motor functions normally. If vacuum was not present, proceed to the next step.

Apply 15 in. Hg vacuum to the rear port of the shift motor. Rotate the right front wheel as necessary and ensure that the outer and intermediate axle shafts are completely engaged. The axles must be completely engaged (i.e., shifted to four wheel drive operation) to open the port for the indicator lamp switch.

Determine if vacuum is present at the port for the indicator lamp switch again. If vacuum was present at the port, the shift motor functions normally. If vacuum was not present at the port, replace the shift motor.

Ok, if at this point it still won't shift correctly you may have a worn shift fork. OEM and replacements are cast and will wear. Posi-Lok 4x4 makes a cast iron fork, about $55.

That should give you some stuff to chew on for a day or so. Post up what you find.

Before I get that deep into it, I'm going to check the u-joints as a friend suggested I do so. The Jeep has 250k miles and from what I'm finding wasnt maintained very well. Thanks for the information though, I appreciate it!

the small line from the firewall to the vac. canister had several cracks, fixed those and the popping went away, for now.