Front axle problem

I have a stock 5 speed, 89 Cherokee 4.0L. I had been noticing a grinding and squealing noise when the wheels were turning. It seemed to go away once I hit 3rd gear. Then I started to feel the whole Jeep vibrate when I hit 25MPH. I parked the thing and pulled the hubs to see if the bearings were bad. both sides seem fine, however, the axle shaft on the passenger side has a real bad scraping/grinding noise when I turn it by hand. I'm not too sharp on diffs, axles, or drivelines in general and I'm not sure what this axle shaft connects to inside the tube. The shaft itself is fatter than the shaft on the driver side. I'm pretty sure that this shaft does not slip directly into the diff but I don't know what is in between the shaft and that diff that would be causing my problems. Any help would be appreciated.

Okay. An '89 5-speed has the vacuum disconnect, which is on the passenger side. Look at the axle tube and you'll see an enlarged, cast iron housing between the differential and the steering knuckle. The shift motor mounts to that.

The shift motor is actuated by vacuum. What is does is move an arm that slides a collar similar to a transmission synchronizer. The inner and outer axle shafts are splined, and when the collar slides to the engaged position it connects the two shafts. When disengaged, it is supposed to slide completely free of one shaft so the outer shaft can free-wheel.

The vacuum tubes happen to be directly under the oil filter, and commonly some oil drips down every time the oil is changed. Eventually the rubber swells and softens, and the harness either falls off or just doesn't maintain a tight seal. If your disconnect is partially engaged, what you're hearing may be the splines in the sliding collar grating on the end of the axle shaft. You can remove the shift motor to check visually whether the shift collar is completely engaged or completely disengaged. Check the condition of the vacuum tubes, as well. Last I knew the harness was still available and cost about $17 -- I carry a spare in my '88 "just in case."

Thanks for the info Eagle. Once again the forum has come to the rescue for me. The shift motor solved the noise problem, however, when I took it out for a test drive I was still getting a lot of shaking and shuddering when I got to around 25MPH. It feels like I have a loose wheel because the faster I go the more it shakes. I now know it's not the bearings or the wheels (torqued them down). Any ideas? Thanks in advance.

May be the axle U-joints, a quick check is to turn the wheel all the way one direction (to check the right, turn right), stick a screw driver into the axle yoke and twist, paying close attention to the rubber seals on the bearing caps. You can see the cross move in the caps, it crushes the rubber seal a bit. Another tip off, is a ring of rust around the bearing cap seal. The U-joints often pop, when turning a tight corner, when they are worn, squeal when they are dry (no grease/washes out). Bad U-joints can vibrate, very similar to an out of balance tire. They are easier to test with the front axle tubes, supported on jack stands.