Here is some info The Adjustable Differential
As stated on the main section page, the term adjustable differential is somewhat of a misnomer as the majority of differentials have some degree of adjustability.
The adjustable differential we refer to in this article is a relatively simple derivative of the open differential. Although there are different designs and implementations they work by the same principle as the example used here.
Adjustable differential that uses Belleville Washers to apply pressure to the sun gears.
This increases the resistance between the gears and stiffens the action of the differential.
As it is adjustable, the 'diffing out' associated with the open differential can be reduced or completely eradicated.
The adjustment is provided by a modified grub screw which allows quick and easy access for track side adjustments.
As far as the internal parts are concerned, they are the same ones that are fitted inside a normal open differential.
If not present on the non-adjustable type, steel thrust washers are fitted behind the the sun gears to stop the forces generated by the belleville washers wearing the casings.