I bought a secondhand disco 1.2 transfer box for my 200tdi defender and before fitting new seals and installing, I wanted to check that it hadn't been retro fitted with an alternative ratio. I realise it's not rocket science but thought that the following might help anyone else wanting to check the same.
My box is already off of the car but it could be easily checked on the car by jacking a rear wheel, removing the PTO cover and paint marking the input gear from the other side.
Rotate the handbrake drum to remove any slack.
Paint a reference mark across the drum and it's back plate.
Paint a mark at 12 o'clock on the input gear
Rotate the brake drum one full revolution so that drum paint marks line up again.
Check the new position of the paint mark on the input gear. It will have moved one complete revolution plus a certain number of 'minutes' after its original 12 o'clock position depending on the final drive. It will be one of 3 positions. If you have the 1.22 drive then it will be 13 minutes past. The 1.4 drive will leave it at 24 mins past. The 1.67 will be 40 mins past.
If you look carefully, you can see my paint mark has indeed moved to the 1.22 position.
Hope that helps someone