Need help with Diff dilema

[ScottH]

Recently picked up a 65 & wanted to check the gear ratio in the rear. So I jacked it up, marked driveshaft & wheel, & turned the wheel.

Was surprised to c the driveshaft started to turn, then stop, then turn a little more, then stop. So tried turning the driveshaft, same results with the tires.

As far as I know its an open rear as the tires turn in opposite directions.
Too damn cold to pull the cover off.

Can anyone shed some light on why this is doing what its doing? I drove the truck b4 buying it, was slow (which is why I want to change the gears), but didnt notice anything out of the ordinary.

Any info, suggestions, opinions would be greatly appreciated.

Thanks
Scott