The drop gears see extreme loads & can often be an area to fail.
The standard helical gears can produce heavy side loads on the bearings, fitting straight cut gears helps reduce this.

These Jack Knight gears feature a worthwhile upgrade, as the idler gear runs on a big central bearing, rather than on two smaller bearings in the gearbox & transfer casing.
This is a much stronger design and should hopefully aid reliability.

The top gear is the primary, the middle the idler & the bottom of the three gears is the 1st motion gear. The Turbo gearbox has a larger nose bearing fitted as standard, this was only done on the Turbo engines, otherwise everything is just standard A+ items.

This shows a worn primary gear which was pitted due to excessive end float. This is scrap.