This is how I confirm differential gearing:
- Raise the rear of the car off the ground onto jackstands. Chock the front wheels.
- Leave the car in neutral, hand brake off.
- Mark the driveshaft visibly along it's axis, about 3-4cm long
- Line up the mark on the driveshaft so it it pointing straight down. You can do that by spinning one of the rear wheels.
- When in position, make a line across the tread of one of the rear tires that lines up with something so you accurately determine when that line has completed a revolution.
- Place your phone camera on the ground pointing straight up at the mark on the driveshaft.
- Press "record"
- Spin the wheel with the line across it's tread 10 times, counting off audibly each time the line makes a complete revolution.
- Stop recording after 10 wheel revolutions are made.
Watch the video. Count off the number of times the mark on the driveshaft makes a revolution. After 10 revolutions of the wheel, the driveshaft will make this many revolutions according to the factory differential gearsets:
(drive shaft revolutions = differential gear ratio)
36 = 3.6
39 = 3.9
41 = 4.1
43= 4.3
47 = 4.7
The first and last of the numbers above are rare, but possible. Good luck!