Chevrolet 70 1969 Series, Shop Manual

Page: 860 / 913

TRANSMISSION AND CLUTCH 7-114
AUXILIARY TRANSMISSION
(3-SPEED-M ODEL 7231A)
OVERHAUL
This section covers service inform ation on Spicer 3-
speed auxiliary transm ission model 7231A (fig. 1) which is
used as optional equipm ent on JM 8 0 M odels.
The transm ission is m anually shifted and has three
speeds forward; underdrive, direct, and overdrive. Gear
shifting is accom plished by use of a shift lever in the cab,
which is connected to the auxiliary transm ission by con­
trol rods. The auxiliary transm ission is m ounted at the
rear of main transmission.
DISASSEMBLY
NOTE: key numbers in text
refer
to Figure 1.
1. M ount auxiliary transm ission in suitable holding
fixture during disassembly operation. Rem ove plug (33)
and drain lubricant.
2. Remove six cover retaining bolts (18) and lock w ash­
ers. Rem ove two cap screws at side of transm ission and
remove parking brake cable bracket. Lift cover (15) up
and away from main case.
3. Lock auxiliary in gear (to keep shafts from turning)
by shifting both clutch collars (10 and 20) into mesh.
4. Rem ove com panion flange lock nuts (24 and 44) using
2-1/8-inch socket. A large im pact wrench will simplify
and speed rem oval of these nuts.
5. Remove front and rear com panion flanges using sui­
table puller. D O N O T H A M M E R O N C O M P A N IO N
F L A N G E S T O R E M O V E O R IN S T A L L .
6. Remove trunnion m ount hanger (front support) from
main drive gear bearing cap (1).
7. Rem ove seven retaining bolts (41) and lock washers
that attach main drive gear bearing cap (1) to case.’
8. Insert two 3/8-16 puller screws at least 2-1/2-inches
long and pull main drive gear (43) and bearing cap (1) as
an assembly. Rem ove gasket (5).
9. Rem ove four cap screws and lock washers from m ain­
shaft rear bearing cap. Rem ove cap and gasket.
10. Remove speedom eter drive gear (23).
11. Slide m ainshaft assembly rearw ard until rear m ain­
shaft bearing (25) is free of case.
12. Use ball bearing puller and remove m ainshaft rear
bearing (25).
13. Remove underdrive sliding clutch gear (21) from rear
of m ainshaft (23). If underdrive clutch gear (21) is a loose
fit on m ainshaft splines it m ay be removed at this time. If
spline fit is tight leave clutch gear (21) in place to retain
m ainshaft underdrive gear (26) during m ainshaft removal.
14. M ainshaft (23) with gear assembly can be removed
from case by lifting front end of m ainshaft up and out of
cover opening.
15. Rem ove four bolts (28) and lock washers from coun­
tershaft rear bearing cap (27). Rem ove bearing cap and
shims (32). Do not lose shim pack.
16. Remove rear bearing cup (31) from case by tapping
on front of countershaft (29). Use a soft ham m er.
17. Slide countershaft (29) tow ard rear of m ain case until
front clears bearing bosses. Lift countershaft up and out
cover opening.
DISASSEMBLY OF SUBASSEMBLIES
SHIFT COVER
Key num bers in text refer to Figure 2.
1. Place cover on work bench and remove poppet retain­
ing plug (10) from side of cover. Rem ove poppet spring
(5) and ball (6).
2. Remove lock wire (9) and set screws (7) from both
shift forks (8 and 11).
3. Pull direct and overdrive shift rod (short rod - 12) out
of fork and cover. Rem ove fork.
4. Rem ove interlock (3) from crosshole in cover.
5. Pull rem aining shift rod (1) out of fork and cover.
Remove fork.
6. Rem ove poppet ball (6) and spring (5) from lower
hole.
7. If shift rod oil seals (2) have been leaking or are d a m ­
aged pry seals out with small pry bar.
MAIN DRIVE GEAR BEARING AND
BEARING CAP (Refer to Fig. 1)
1. Rem ove drive gear (43) from bearing cap (1) by sup­
porting assembly on a 6-inch I.D. tube and pressing on
splined end of shaft.
2. Push bearing spacer (3) aside and use drift to tap
drive gear front bearing (2) and oil seal out front of cap.
3. Rem ove snap ring (42) and tap or press drive gear
rear bearing (4) out rear of cap.
MAINSHAFT AND GEARS (Refer to Fig. 1).
1. Slide or tap m ainshaft underdrive gear (26) and clutch
gear (21) rearw ard from m ainshaft (23).
2. Rem ove direct and overdrive sliding clutch collar (10)
from m ainshaft overdrive and direct clutch gear (13).
3. Remove retaining snap ring (9) from m ainshaft and
remove direct and overdrive clutch gear (13). Slide over­
drive gear (16) forw ard from m ainshaft.
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK S H O P M A N U A L