Now that I temporarily reside in Ireland and have acquired an ATR and also ATR spare U2Q7 transmission, I got my hands on a service manual.
Here is the info from it for everyones information (and to clear up that it is 100% not a viscous-type LSD like USDM lsds, etc):

Limited Slip Differential (LSD) (H22A7 engine model)

Function
Operation of the helical type limited slip differential (LSD) is dependent upon the eight pinion gears that are in mesh with the two side gears. They transfer the driving power to the driving axles as well as permit the outside wheel to turn more times than the inside wheel when the vehicle goes around a turn. All gears are helically cut so that this differential action is limited by the friction created between each gear and differential carrier when either wheel slips.

Construction
The unit consists of the two side gears, four short pinion gears, four long pinion gears, two thrust washers, a center washer, and a carrier that houses the gears and washers. One short and one long pinion gear are in mesh with each other and are allowed to walk around the side gears.



When rounding a curve
When the vehicle rounds a curve, the differential allows the outer wheel to rotate a little faster than the inner wheel. When this takes place, the short and long pinion gears rotate, and walk around the side gears in the directions shown. If, for example, the right shaft is rotated in a counterclockwise direction with the differential carrier held stationary, the force is transmitted through the right side gear, short pinion gears and long pinion gears to the left side gear, causing the left shaft to rotate in a clockwise direction. This allows the outer wheel to turn more times than the inner wheel when the vehicle goes around a turn.

When limiting differential action
The limited slip differential (LSD) acts to limit the differential action when either wheel slips on ice or snow or on turn. This is done by using the friction created between each gear and differential case:
(1) The pinions are forced against the differential carrier by the force as they are rotated and repelled outward in engagement.
(2) The ends of the pinion gears are held firmly against the differential carrier due to the side thrust from the helically cut gears.
With the pinion gears locked, the torque applied to the slipping wheel is reduced and the torque delivered to the other wheel is increased.

 

hey so i know this is a very old post and it helped me a lot when i purchased my u2q7... but ive gotten a lot of feedback from various places that an aftermarket differential, say a quaife, deisigned for the average h22 transmission will not fit into the u2q7 or t2w4 type/euro r transmissions. something about clearance because the helical diff uses a smaller housing? hoping that if you are still a frequent user on H-T that you could help me out. thanks man.



also gotta say, ive seen your dyno vids and read a lot about your lude, very impressed and inspired by your setup.