TM 9-2320-266-34
(1) Move the selector lever slowly upward until it
Table 4-2. Automatic Shift Speeds and
clicks into the "P" notch in the selector gate. If the starter
Governor Pressure Chart (Approximate MPH)
will operate, the "P" position is correct.
Axle Ratio: 4.10:1
Tire Size: 9.50R 16.5D
(2) After checking the "P" position, move the selec-
tor slowly toward the "N" position until the lever drops at
Condition
MPH
the end of the "N" stop in the selector gate. If the starter
Throttle closed
will also operate at this point the gear selector linkage is
1-2 upshift
8-10
properly adjusted. If adjustment is required, refer to para-
2-3 upshift
11-13
graph 4-10.
3-1 downshift*
7-9
d. Throttle Linkage. The throttle rod adjustment is very
Throttle wide open
important to proper transmission operation. This adjustment
1-2 upshift
23-31
positions a valve which controls shift speed and quality, and
2-3 upshift
49-56
part-throttle downshift sensitivity. If the setting is too short,
early shifts and slippage between shifts may occur. If the set-
Kickdown range
ting is too long, delayed shifts and sensitive part-throttle
3-2 downshift
42-51
downshifts can result. In fact, this adjustment is so critical
3-l downshift
20-23
that the use of a throttle lever holding spring is necessary to
Governor pressure
remove slack in the linkage during adjustment.
15 psi
15-18
e. Road Test.
50 psi
36-39
75 psi
50-54
(2) Prior to performing a road test, be certain that the
fluid level and condition, and the control linkage adjustments
*Governor preseure should be from zero to 1.5 psi at stand-still or
have been checked and approved.
downshift mey not occur.
(2) During the road test, operate the transmission in
by leaking hydraulic circuits or sticking valves.
each position to check for slipping and any variation in
shifting. Note whether the shifts are harsh or spongy, and
(d) Unless the condition is obvious, like no drive
check the speeds where the upshifts and downshifts occur.
in the "D" range first gear only, never disassemble the trans-
Approximate shift speeds for the various modes of operation
mission until hydraulic pressure tests have been performed.
are shown in table 4-2.
4-4. Hydraulic Pressure Tests.
(3) Observe the vehicle closely for transmission slip-
a. General. Pressure testing is a very important step in
page. Slipping in any gear usually indicates clutch, band, or
the diagnostic procedure. These tests usually reveal the cause
overrunning clutch problems. If the condition is far ad-
of most transmission problems. Before performing pressure
vanced, an overhaul will probably be necessary to restore
tests, be sure that the fluid level and condition and the link-
normal operation.
age adjustments have been checked. Fluid must be at oper-
(4) In most cases, the clutch or band that is slipping
ating temperature.
can be determined by noting transmission operation in all
NOTE
selector positions, and by comparing which internal units are
applied in those positions. Table 4-2 provides a basis for
Do not let the truck move while the trans-
road test analysis.
mission is operating during these tests. On
4X4 models, put the transfer in neutral.
(a) The rear clutch is applied in both the "D" first
On 4X2 models, chock the front wheels,
gear and "1" first gear positions. The overrunning clutch is
raise the rear wheels, and remove any for-
applied in "D" fiist and the low and reverse band is applied
eign objects from the tires.
in "1" first. If the transmission slips in "D" range first gear
but does not slip in "1" first gear, the overrunning clutch is
b. Preparation for Testing.
the unit that is slipping. Similarly, if the transmission slips
in any two forward gears, the rear clutch is the slipping unit.
der the vehicle.
(b) Using the same procedure, both the rear and
(2) Disconnect the throttle rod and shift it from the
front clutches are applied in "D" third gear. If the trans-
transmission levers so they can be controlled under the
mission slips in third gear, either the front or rear clutch is
vehicle.
slipping. The slipping unit is determined by selecting another
gear which does not use one of those units. If the transmis-
(3) Attach a 100 psi gage to the ports required for the
sion also slips in "R" (Reverse), the front clutch is slipping.
test being conducted. A 300 psi gage is required for a
If it does not slip in "R", the rear clutch is slipping.
"reverse" pressure test at the rear servo. Test port locations
are shown in figures 4-10 and 4-11.
(c) Use this process of elimination to detect a
slipping unit, and to confirm proper operation of good units.
c. Test One (Selector m "1").
However, although road test analysis can usually diagnose
(1) Attach the gages to the line and rear servo ports.
slipping units, the actual cause of the malfunction usually
(2) Operate the engine at 1,000 rpm.
cannot be decided. Practically any condition can be caused
4-12
