Series 2A Differentials

[danniboy]

Happy New Year one and all.
Does anyone know if the complete differential is interchangeable from the back to the front of the vehicle. I have a spare differential from a 1966 109 which I want to put into the front axel of my 1962 series 2a. The 109 diff has a flat with two holes in it made onto the outside of the casting for some strange reason. It also has a R stamped on it and Rover with some numbers.
Any comments greatly appreciated.
Cheers

[JDNSW]

Differentials are interchangeable front to rear, although the rear one needs to have a filler plug on the nose of the diff unless there is a level/filler plug in the housing. (front axle housing should have a plug)

A couple of checks -

Count the teeth; All Series 2a differentials are 4.7:1, 10 teeth on the pinion and 47 on the crown wheel. But you may not have standard ratios in your 2a, or possibly in the spare, so make sure they are the same.

The Rover diff was interchangeable in general terms from the 1930s through to Discovery 1 including Rangerover, although ratios varied, and there were differences in seals and appearance. Check that the splines on the sun gears are the same as your half axles (should be ten) and that the pinion flange matches the U-joint on your prop shaft.

Your description sounds like the diff in question is a Series 3 or later, and it may have been fitted to the axle to provide a different ratio, so to repeat, count the teeth.