Re: 1999 grand cherokee 4.7
As told before, the problem with the 4all time is the T-case. On the WJ no electronics involved in the 4 wheel drive system. If you have the NV247 T-case, then the problem could be low fluid, but more probably the progressive coupler inside the T-case.
As for the ABS fault codes, best would be to reset them and see if they come back. The G-sensor (depending on model year), is a separate unit under the rear seat carpet next to where the parking brake cables go through the floor( newer models have this G-switch integrated into the electronic control module, the CAB (Controller Antilock Brake)). The G-switch contains 3 mercury switches and sends deceleration signals to the CAB. Is the ABS light on the instrument cluster on as well?
And look for an other parts house, because there is no 4 WD switch on the WJ.