GMC T Series 1994 Repair Manual page 820

• Roller bearings support the mainshaft indepen­
dently in the drive gear.
• The drive gear and mainshaft are engaged by a
synchronizer for direct drive in top gear.
• Thrust washers limit the play of the mainshaft.
4. Reverse idler gear.
• The idler gear drives the mainshaft in reverse.
• The idler gear is supported on its own shaft.
5. Shift lever.
• The shift lever is mounted on the extension
housing.
• The shift lever moves the shafts which are
mounted in the transmission top cover.
• Shift forks mounted on shafts move the syn­
chronizers to engage the gears.
• A pin-type interlock blocks the other shafts
when one is moved.
PRECAUTIONS
Certain precautions should be followed when repair­
ing the transmission. Unless proper care is taken, the
components may be damaged.
• Repair of a transmission should be done in a clean
work area. The outside of the case should be clean
to keep dirt out of the transmission. On transmis­
sions with a standard gearshift lever, install the
lever before cleaning the outside of the transmis­
sion.
• During transmission repair, all the parts should be
cleaned in cleaning solvent and then air dried. Wip­
ing cloths or rags should not be used to dry the
parts as lint may get on the parts and cause trou­
ble later. All the parts, except those being worked
on, should be kept covered with clean paper.