The Back End on my car was one of the things that took a bit of getting right. Close inspection shows that I've used Kombi reduction gears, called in the trade 'Droppers'. My first car was essentially all Kombi, and the whole concept arose, not because I knew anything about 'torque reaction', but because I owned a 'real' Kombi and I knew how good the traction was on that car. In fact, I used to practice getting stuck in the mud before I knew anything about trials. At least the trials 'legitimised' this foolish practice.
Torque reaction is the key, and the droppers promote quite violent torque reaction which attempts to lift the car, in turn pushing the tyres down hard on the ground and thus increasing traction. This is actually a momentary thing but it lasts until the limit of travel is reached, quite often long enough to get the best of a section. Letting the car squat by applying the fiddle brakes, then using the throttle to make the car jump is a great technique to master.
A side benefit of the droppers is the 4" extra ground clearance.
Standard Kombi back-ends that use
reduction gears are all 'swing-axle' types. Mine is fully
independent ala later model Kombis, but with the droppers
attached. I use this system, rather than a more adjustable
set-up with say, transverse links, radius arms & struts,
because there are less links to buy, and the layout is more
robust when it comes to driving over things that might snag
the underneath of the car. I remove plenty of weight from
dropper. The original axle (to
the gearbox) is cut off and a flange from a normal IRS VW
(Green arrow) is pressed & welded onto the remaining
Yellow arrow indicates the amount of material removed. The original bearing inside this side of the dropper is replaced with a sealed type, so no extra seal is necessary. Spring plate - blue arrow - is sandwiched between trailing arm & dropper. The spring plate bolt hole pattern is different (slightly) on the Kombi, so I add 1" to the car type I use, and drill two holes in that bit. Back