Speed Gears

Check that the helical and clutch gear tooth surfaces are not damaged or worn.
Check that the synchronizer cone surfaces are not roughened, damaged or worn.
Check that the gear inside diameter and front and rear surfaces are not damaged and worn.

Fig 1: Helical, Clutch Gear Tooth Surface, Synchronizer Cone Surface And Gear Inside Diameter

Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.