GMC 1982 Light Duty Truck, Руководство по обслуживанию

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MANUAL TRANSMISSION 7B-1
MANUAL TRANSMISSION
CONTENTS
General Description..........................................................................................7B-1
M aintenance and A d ju s tm e n ts .................................................................... .7B-2
Free Pedal T r a v e l ...........................................................................................7B-2
Spin Down T i m e ............................................................................................ .7B-2
Shift E ffo rt...................................................................................................... .7B-3
Transmission A lignm ent.............................................................................. .7B-5
Diagnosis...............................................................................................................7B-6
7 6 M M (3 S p e e d ) ............................................................................................. ..7B1-1
7 7 M M (3 S p e e d ) ............................................................................................. ..7B2-1
8 9 M M (4 S p e e d ) ............................................................................................. ..7B3-1
117M M (4 S p e e d ) ........................................................................................... ..7B4-1
GENERAL DESCRIPTION
THREE-SPEED T R A N S M IS S IO N S synchronizing the speeds of m a tin g p arts before they
engage.
3-S peed 7 6 m m (7B 1-4)
76mm driven gear, second speed gear,
first speed gear and reverse gear are rigidly connected to the
_ - ,
7 7
c
7
d o countergear. In the 77mm transmission, only the driven
J o p e e a
m m
^ -
)
g e a r^ seconcj Speed gear and first speed gear are rigidly
M an u al transmissions are designated according to: (A) connected to the countergear. The engine driven clutch gear
th e num ber of forward gears, and (B) the measured distance drives the c o u n te rg e a i th rough a c o n s ta n t mes
between centerlines o f th e mainshaft and the countergear. c o u n te rsh a ft driven g ear. T h e c o u n te rg e a r ro tates in a
direction opposite, or counter, to the rotation or the clutch
T h e th re e speed synchrom esh transm ission a re «e a r ' Forward sPe,,ed «ears ° " ,he countergear re m a i" in
representative of a co n stan t-m csh transm ission design. “ nstanf " e s h w i t h two nonshdmg mainshaft gears giving
Fundam ental components of these units are the case, which fi,rst and second speed Third speed is a direct drive with the
house the gears and shaft; the shift control mechanism and clutch «ear en8 a8 ed dl r f c ' he ™ ' " sh a ft- Fo™ ard
the various shafts and gears. The input shaft has an integral 8ears a r.e en* a* ed through two sliding synchronizer sleeves
main drive g ear and rotates with the clutch driven plate; m ou" ted o n ‘hff mainshaft. Engagement of the constant
that is, the shaft rotates all the time the clutch is engaged ™ sh ™ ! ns*aft .gears t0 the ™a ' " shaft 15 accomplished
and the engine is running. T he input shaft is supported in the th ro u § h blocker n n «-, >'Pe synchronizers.
case by a ball bearing and at the front end by an oil ,n Tn * M C i n c c i A M
, j i i & , j • ,i i u r* F O U R -SPEED T R A N S M IS S IO N
im pregnated bushing mounted in the engine crankshaft.
The drive gear is in constant mesh with the countershaft
4 - S p e e d 8 9 m m (Fig. 7 B 3 - 4 )
drive gear. Since all gears in the countershaft cluster are The four speed transmission with overdrive has an
integral to the shaft, they also rotate at the time the clutch is 89mm center distance and is designed to combine normal
engaged. T he countergear is carried on roller bearings at performance in the city with improved fuel economy on the
both ends and thrust is absorbed by thrust washers located hig hw ay. Gear ratios are: first 3.09 to 1; second 1.67 to 1;
between the countergear and thrust bosses in the case. The third , 00 t0 1; fourth (overdrive) 0.73 to 1. All forward
transmission mainshaft is held in line with the input shaft by gears are fully synchr 0 nized. The synchronizer assemblies
a pilot bearing at its front end, which allows it to rotate or consist of a hub, sleeve, two key springs and three
come to rest independently of the input shaft. In the 76m m synchronizer keys. The synchronizer hubs are splined to the
unit, the mainshaft is carried at the rear by a ball bearing mainshaft and retained by snap rings. These assemblies
mounted in the front face of the extension housing. In the perm it gears
t0
be seiected w ithout clashing, by
77mm unit, the mainshaft is carried at the rear by a ball synchronizing the speeds of m atin g p arts before they
bearing mounted in the rear of the case. PMQ()P
Helical gears are incorporated throughout, except for The drive pinion (input shaft) is supported by a ball
reverse gear in the 77 mm transmission. The mainshaft gears bearing in the transmission case and an oil impregnated
are free to rotate independently on the mainshaft and are in bushing pressed in the end of the crankshaft,
constant mesh with the countershaft gears. The reverse idler The mainshaft front end is supported by roller bearings
gear is carried on a bushing, finish bored in place, and thrust jn the end of the main drive pinion and a ball bearing in the
is taken on the thrust bosses of the case. front of the extension housing. T he o u tp u t end of the
The transmissions are fully synchronized in all forward mainshaft is splined to the sliding universal joint yoke,
speeds; however, reverse g ear is not. T h e synchronizer which is supported by a bushing in the extension housing,
assemblies consist of a hub, sleeve, two key springs and three The countershaft gear is supported by a double row of
synchronizer keys. The synchronizer hubs are splined to the needle type roller bearings at each end and the thrust is
mainshaft and retained by snap rings. These assemblies taken on thrust washers between the ends of the gear and the
perm it gears to be selected w ithout clashing, by transmission case. The alignment of the needle type roller