The inspection of the primary shaft, its gears and bearings is similar to the inspection of the secondary shaft (see "Repair of the secondary shaft").
You will need: a universal puller, a hammer, a mandrel.

To replace rear bearing 3, press it out using a puller and press the new bearing in until it stops using a suitable mandrel, applying force only to the inner ring of the bearing. When replacing the front bearing, note that a thrust ring 2 is installed under its inner ring 1 on the shaft.
