1 . Thoroughly clean each gearbox component and, if available, blow them dry with compressed air. Carefully inspect each part for wear or damage. Any part that has a thrust or friction surface showing a blue color should* be replaced. This indicates that part has been subjected to excessive heat.
Checking The Gearbox Components For Wear
2. Carefully check the teeth on all the gears for excessive wear or damage. If you find such damage on one gear, be particularly careful about inspecting its opposing gear on the other shaft, as it may be damaged also.
3. The engaging dogs on all the gears and the condition of the 4th and
5th gear sliding dog should be inspected. If any of these dogs have excessively
rounded edges, they should be
replaced. This could cause two engaging gears to "reject" each other, or miss a shift. Also, be sure that the sliding gears and engaging dog are free to slide back and forth on their shafts.
4. If the transmission is being repaired because of broken gear teeth
or a foreign object in the gearbox, or some other breakage resulted in
sudden stoppage of the gearbox and drive train, the mainshaft and layshaft
should be checked for straightness. They may have been bent due to high
loading forces created when such things occur. Place the shaft being checked
in a set of machinist's centers fitted with one dial indicator, as shown
in Fig. 38. Position the indicator on the middle of the shaft and then
rotate it slowly. If the indicator shows a runout of over .001-, replace
the shaft. Also, when breakages of this type occur, check the condition
of the transmission bearings and bushings.