Chevrolet 10 Series 1968, Service Manual, Page: 503 / 713

CLUTCHES AND TRANSMISSIONS 7-40
OTHER SERVICE OPERATIONS
Although certain operations, such as oil pan, gasket or
manual levers and oil seal replacement, valve body,
governor, fille r pipe “
0
” ring, speedometer drive gear,
case extension " O " ring and rear oil seal, vacuum
modulator, and servo cover or gasket service may be
performed from underneath the vehicle without removing
the Powerglide; their service procedure is covered in the
Truck Overhaul Manual and is not repeated here. Refer
to the Powerglide Section of the Truck Overhaul Manual
for all other service operations not covered here.
DIAGNOSIS
Proper operation of the Powerglide transmission may
be affected by a number of factors, all of which must be
considered when trouble in the unit is diagnosed.
Proper trouble diagnosis can only be accomplished
when performed in a thorough step by step procedure.
The following procedure has been devised and tested and
is recommended for all trouble diagnosis complaints and
if the service man will follow this checking procedure,
accurate and dependable diagnosis may be accomplished.
This will result in a savings of time, not only to the serv­
ice man, but to the customer as well.
WARMING UP TRANSMISSION
Before attempting to check and/or correct any com­
plaints on the Powerglide transmission it is absolutely
essential that the oil level be checked and corrected if
necessary. An oil level which is either too high or too
low can be the cause of a number of abnormal conditions
from excessive noise to slippage in all ranges.
It must be remembered that cold oil will slow up the
action of the hydraulic controls in the transmission. For
this reason a trouble or oil leak diagnosis should not be
attempted until the transmission has been warmed up by
either of the following procedures:
Shop Warm Up
1. Connect tachometer to engine.
2. Set parking brake tight and start engine.
3. Place selector lever in “ D " (drive) range.
4. Adjust carburetor idle speed adjusting screw to run
engine at approximately 750 rpm and operate in this
manner for two minutes. At the end of two minutes
of operation, the transmission will be sufficiently
warmed up for diagnosis purposes.
NOTE: At this point, readjust the engine idle
speed to 450-475 rpm in “ D” range.
Road Warm Up
Drive the vehicle approximately 5 miles with frequent
starts and stops.
N OTE: At this point, make sure the engine idle
speed is set to 450-475 rpm in "D ” range.
CHECKING FLUID LEVEL AND CONDITION
After transmission has been warmed up, check the fluid
level with the engine idling, parking brake set and con­
trol lever in “ N” (neutral). If the fluid level is low, add
fluid to bring level up to the full mark on gauge rod.
C A U TIO N : If fluid level is too high, fluid may
be aerated by the planet carrier. Aerated fluid
will cause turbulence in the converter which will
result in lost power, lower stall speed and lower
pressures in control circuits. Lower fluid level
to full mark, then shut off engine to allow air
bubbles to work out of fluid.
When checking oil level, a burned smell and discolora­
tion indicate burned clutches or bands and the transmis­
sion will have to be removed.
MANUAL LINKAGE
Manual linkage adjustment and the associated neutral
safety switch are important from a safety standpoint. The
neutral safety switch should be adjusted so that the engine
will start in the Park and Neutral positions only.
With the selector lever in the Park position, the park­
ing pawl should freely engage and prevent the vehicle
from rolling. The pointer on the indicator quadrant
should line up properly with the range indicators in all
ranges.
OIL LEAKS
Before attempting to correct an oil leak, the actual
source of the leak must be determined. In many cases the
source of the leak can be deceiving due to "wind flow’ ’
around the engine and transmission.
F ig . 5 P G —Pressure Test Plug
CHEVROLET TRUCK SERVICE MANUAL