[Richard]

No need to pull the diff covers to get the ratio. Put a mark on the drive shaft and a mark on the wheel. Chock the front wheels, put trans in neutral, jack up one rear wheel and rotate one revolution. Count the times the driveshaft turns. Just over 3=3.08, just under 4=3.73, just over 4=4.10, you get the idea. If there is a locker in the diff both rear wheels will need to be off the ground.