A few questions for the T16 experts out there.

[David Herbert]

I very much agree with Lynn.
Driving in a straight line the sprockets have the same number of teeth and are turning at the same speed. This means that the tracks are being pulled round the sprockets at the same number of links per minute. If one track is more worn/stretched than the other the pitch is longer and that track travels further so you slowly turn. If one track is more worn than the other it would often result in it having a link or two removed so that it can be tensioned but the cause of the drifting is the difference in pitch due to wear. Any difference in the number of links is incidental but indicates different pitch. As has been mentioned, if everything else is equal, different tension on each side will also cause drifting but simply because a tighter track has more drag so the vehicle will tend to drift towards that side.

David

[rob love]

I guess the best analogy would be having two different size tires on an axle. A 9.00-20 on the left and a 11.00x20 on the right just won't work well.

Regarding the differential moving to the front, the armoured snowmobile (and the later penguin variants) used a T-16 differential on the front, but the designers made the neccessary changes to flip the gearbox over, thus being able to run the engine and transmission directly into the diff.

[David Herbert]

As the pinion is at the same hight as the crown wheel it should be possible to flip the crown wheel, controlled differential and brake drums assembly within the housing to engage the other side of the pinion. It will need setting up for backlash but looking at the photos above and the manual I can't see why this can't be done. It would be dead easy and saves extra/special gearboxes.
David