The biggest weakness of the 02m 02q gearboxes is the fourth gear.

With high engine torque, the input shaft vibrates and the opposite side shaft pushes the gears outward. The fourth gear therefore no longer functions correctly to the point of deteriorating and breaking!

The reinforcement works like this:
A brass mandrel is pressed against the shaft by means of a bolt (adjustable ) , which makes it possible to hold the shaft but also to form a sliding bearing between the brass axle and the input shaft.