Re: no 4 wheel drive
Welcome to the garage.
With front drive shaft you mean the propeller shaft between T-case and differential? So when is it not turning?
Is this a quadra drive or quadra trac?
The propeller shaft is always connected to the differential, so when the jeep moves, the front propeller shaft turns.
If the jeep is quadra drive or quadra trac, it has the NV 247 T-case. This T-case has a progressive coupler which will transfer torque to the front wheels when there is a speed difference between front and rear propeller shafts.
Many times this progressive coupler doesn´t work anymore, but first check the fluid level in the T-case. If it is low, it should be filled with special Mopar fluid, which is Mobil 424 fluid.
Repair of the progressive coupler is not possible and it should be changed as a unit, which is quite expensive. A junk yard T-case or even a NV 242 T-case are probably better alternatives.