"Katmandu" wrote in a message:
Put a mark on the tire, and on the driveshaft, or the yoke, and count the number of revolutions the driveshaft makes to 1 revolution of the tire. The driveshaft will turn slightly less than 4 turns to one turn of the tire if they are 3.91's. To check for a locker, with both tires off the ground, turn one tire, and watch the other one. Both tires should turn in the same direction. Also, when driving the car, when making a relatively hard turn, you will hear a clicking noise coming from the rear end. Hope this helps.