How to tell diff ratios?

[Knightmayre]

The previous owner told me it had 4.11's fitted and I have no clue how to find out.
It feels terribly slow pulling off, going through the gears like a Russian Ural truck.

[MudRunnerTD]

Hi mate. You can do it a couple of ways. If they have been swapped then the compliance plate wont match.

Pull the diff out and count the teeth on crown wheel and pinion.

Jack the back diff off the ground and slowly spin the back wheels and count how many times the drive shaft turns. Put a mark on the drive shaft and ask someone to slowly turn the back wheel while you count the spins. Your looking for 1:3.9 or 1:4.1 or 1:4.3 or 1:4.6 revolutions of the tailshaft for 1 turn of the back wheels.