97 awd

i own a 97 explorer awd 5.0 with 188000 miles on it.when i put the car in drive and take my foot off the brake and roll slowly i hear a clicking noise coming from under the car which goes away when i accelerate the noise is in the center of vehocle when i put it on the lift the noise goes...

Before I even spend $20 I'd like to check my rear abs sensor. Any idea on what range it should read on an ohm meter? Front ones too if you've got that info. But both front read the same.97 xlt awd 5.0L