96 XLT 4.0L 4x4 works intermittently

[Ataractic]

I was doing a little mudding the other day and noticed that my 4x4 was going on and off intermittently. The 4x4 light stayed on constantly, but the front tires would spin for a bit, then not spin... back and forth. Eventually, they spent more time not spinning than spinning. Had to get towed back to the road. When I put it in 4wd on the pavement it feels like it is engaging, can tell there is more resistance on the drivetrain. Here's what I know so far:

Put it on the lift, 4wd low in neutral engine off:
- Could spin front tires, but only maybe 1/2 a turn in either direction before it wouldn't turn anymore.
- Spinning one tire did not cause the other to spin
- Spinning front driveshaft caused only one tire to spin
- Spin rear driveshaft forward caused both rear tire to spin in the same direction, spin in reverse only one wheel turns.
- Spinning rear driveshaft does not cause front to spin.
- Can spin the rear driveshaft freely, doesn't meet resistance like the front.

Any ideas?

 

[gmanpaint]

Control Trac + CAD.

Sounds to me that the Central Axle Disconnect is not working. Check the obvious first.

There is a few components in this system you can look over easily. Behind the Pass side headlights is a relay box with hard vac lines connected to the diff and a round plastic ball on the fender liner. Check all the vac line connections and than the relays. If they all check out fine, you can remove the inspection plate on the diff itself without dropping the diff. It has a gasket on it so either be super careful or plan on replacing it.

Inside you will find a shift fork that separates the pass side axle from each other. It may have busted. You will lose a little fluid when doing this, so check the level and top it back off or change it all out with some fresh Synthetic 80-90 wt.