The above link is good yet perhaps confusing. Basically you can jack up one rear wheel, turn it a few times, count how many turns the driveshaft makes, and do some math.
In only a few words:
A good and accurate way to do that is to turn the driveshaft 20 turns, let only one wheel turn and count the turns(assuming open differential/no locker). Now 10 divided by number of wheel turns is your ratio.
Your 48 1.5 ton has a normal open diferential, so that method works nicely.
To further explain why this works is because the differential gears throw in a factor of 2. So we used 20 turns and calculated with 10 because 20/2=10, so that accounts for the action of the differential when you only had one wheel turning.
Last edited by Grigg; 12/17/2013 9:18 PM. Reason: clarify
