GMC 1989 Light Duty Truck, Repair Manual, Page: 913 / 998

NEW PROCESS TRANSMISSION 7B3-1
SECTION 7B3
NEW PROCESS TRANSMISSION
CONTENTS
SUBJECT PAGE
D escription....................................................................................................................................................................................7 B 2 - 1
Disassembly of the T ra n s m is s io n ........................................................................................................................................ 7 B 2 - 3
Disassembly and Assembly of Sub-Assem blies................................................................................................................7 B 2- 6
Main Drive G e a r ...................................................................................................................................................................... 7 B 2 - 6
M a in s h a ft................................................................................................................................................................................. 7 B 2 - 6
C o u n te rg e a r............................................................................................................................................................................. 7 B 2 - 8
Extension Housing..................................................................................................................................................................7 B 2 - 8
Main Drive Gear Bearing R e ta in e r .................................................................................................................................... 7B 2- 9
Side C o v e r ............................................................................................................................................................................... 7 B 2 - 9
Transmission Assembly (Installation of Sub-Assem blies)............................................................................................. 7 B 2 -1 0
S p e c ific a tio n s ............................................................................................................................................................................. 7B2-11
Fastener T o rq u e............................................................................................................................................................... . .7 B 2 -1 1
L u b rica tio n ............................................................................................................................................................................... 7B2-11
Special T o o ls ............................................................................................................................................................................... 7 B 2-12
DESCRIPTION
The New Process 89 mm 4 speed transmission (RPO
MY
6
) is an overdrive transmission and is fully synchro­
nized in all speeds except reverse (figure
1
).
The main components are:
1.
Main drive gear.
• An integral shaft is splined to engage with the
clutch driven plate.
• The gear drives the countergear.
• A ball bearing supports the shaft in the case.
2.
Countershaft.
• The countergear is keyed to the countershaft
for constant rotation with the main drive gear.
• Roller bearings align the countergear on the
shaft.
• Thrust washers and a spacer limit the coun­
tershaft end play.
• The countershaft is not a press fit, and a plug
seals the case bore.
3.
Mainshaft.
• The drive gears rotate freely on the mainshaft
and are in constant mesh with the counter­
gear.
• Key type synchronizers are splined to the
mainshaft and engage with the drive gears to
turn the mainshaft.
• A ball bearing supports the mainshaft in the
extension housing.
• Roller bearings support the mainshaft inde­
pendently in the input shaft.
• The input shaft and mainshaft are engaged by
a synchronizer for direct drive in top gear.
4. Reverse idler shaft.
• An idler gear drives the mainshaft in reverse.
• A bushing supports the gear on the shaft.
5. Side cover.
• Shift forks mounted in the cover move the syn­
chronizers to engage the gears.
• The reverse shift lever and a detent ball and
spring are mounted in the case.
Certain precautions should be followed when repairing
the transmission. Unless proper care is taken, the compo­
nents of the transmission may be damaged.
• Repair of the 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 trans­
missions with a standard gearshift lever, install the
lever before cleaning the outside of the transmis­
sion.
• During the transmission repair, all the parts should
be cleaned in cleaning solvent and then air dried.
Wiping cloths or rags should not be used to dry the
parts as lint may get on the parts and cause trouble
later. All the parts, except those being worked on,
should be kept covered with clean paper.