Before disassembly, remove the inspection cover.
This will allow you to observe transmission action.
Shift the transmission into each gear, and, at the same
time, rotate the input shaft while inspecting the
conditions of the gears and synchronizers.
The basic disassembly procedures are as follows:
1. Unbolt and remove the rear extension housing.
It may be necessary to tap the housing off with a
soft face mallet or bronze hammer.
2. Unbolt and remove the front extension housing
and any snap rings.
3. Carefully pry the input shaft and gear forward
far enough to free the main shaft.
4. Using a brass driftpin, push the reverse idler
shaft and countershaft out of the transmission
5. Remove the input shaft and output shaft
assemblies. Slide the output shaft and gears out
of the back of the transmission as a unit. Be
careful not to damage any of the gears.
After the transmission is disassembled, clean all
the parts thoroughly and individually. Clean all the
parts of hardened oil, lacquer deposits, and dirt. Pay
particular attention to the small holes in the gears and
to the shifter ball bores in the shifter shaft housing.
Remove all gasket material using a putty knife or other
suitable tool. Ensure that the metal surfaces are not
gouged or scratched. Also, clean the transmission
bearings and blow-dry them using low-pressure
Always use protective eyewear when you
are blowing the bearing dry with compressed
air. Do NOT allow the bearing to spin. Air
pressure can make the bearing spin at
tremendously high rpm, possibly causing the
bearing to explode and fly apart.
After all parts of the transmission have been
cleaned, inspect everything closely to determine
whether they can be reused or have to be replaced. The
wear or damage to some of the parts will be evident to
the eye. If brass-colored particles are found, one or
more of the synchronizers or thrust washers are
damaged. These are normally the only transmission
parts made of this material. If iron chips are found,
main drive gears are probably damaged. To check for
damage or wear on other parts, it may be necessary to
use measuring tools and gauges to determine their
Any worn or damaged parts in the transmission
must be replaced. This is why your inspection is very
critical. If any trouble is NOT corrected, the transmis-
sion overhaul may fail. You would have to complete
the job a second time, wasting man-hours and
materials, as well as unnecessary equipment down-
Always replace all gaskets and seals in the
transmission. Even though the seal or gasket may have
not been leaking before disassembly, it may start to
leak after assembly.
When replacing a main shaft gear either due to
wear or damage, you should also replace the matching
gear on the countershaft. If a new gear is meshed with
an old gear, transmission gear noise will occur.
If new bolts are needed, make sure it is the correct
thread type and length. Some transmission use metric
bolts. Remember mixing threads will cause part
All parts must be lightly coated with a medium-
grade lubricating oil. This is done immediately after
the inspection or repair. Oiling the parts give them a
necessary rust-preventive coating and facilitates the
After obtaining new parts to replace the worn or
damaged parts, you are ready for transmission
assembly. To assemble the transmission, use the
reverse order of disassembly. Again refer to the service
manual for exact directions, as well as proper
clearances and wear limits of the parts. The service
manual will have an exploded view of the trans-
mission. It will show how each part is located in
relation to the others. Step-by-step direction will
accompany the illustrations.
Certain key areas of the transmission should be
given extra attention during assembly. One area is the
needle bearings. To hold the needle bearings into the
countershaft or other shafts, you coat the bearings with
HEAVY GREASE. The grease will hold the bearing in
place as you slide the countershaft into the gears. Also,
measure the end play or clearance of the gears and
synchronizers and the countershaft and case as
directed by the service manual.
Before installing, ensure the transmission shifts
properly. This will save you from having to remove the
transmission if there is still problems. Also, since the
transmission is already out, this is an ideal time to
inspect the condition of the clutch.