3–24 Copyright © 1996 General Motors Corp.
AT 500, 1500 SERIES AUTOMATIC TRANSMISSIONS
Table 3–11. Main Pressure Check Procedure
(Models With Modulated Main Pressure)
Table 3–12. Retarder Pressure Check Procedure
WARNING!
Observe safety precautions during hydraulic pressure check procedures. All personnel must stand clear
of the vehicle. Take precautions against movement of the vehicle. Be sure that gauges (vacuum, pressure,
tachometer) have extended lines so that they can be read from inside the vehicle.
NOTE:
Perform procedures (1), (2), (3), (4), and (5) from Table 3–10.
VACUUM MODULATOR MECHANICAL MODULATOR
Install a tee in the modulator line and connect a
vacuum gauge to measure pressure.
Disconnect the modulator cable from the throttle linkage.
NEUTRAL Make sure there are 15 inches or more vacuum.
Main pressure should be 90–110 psi
(621–758 kPa).
Push or pull the cable to the idle position against the
internal stop. Main pressure should be 90–110 psi
(621–758 kPa).
If main pressure is 135–155 psi (931–1068 kPa), the transmission has demodulated main pressure.
Use Table 3–10.
Push or pull the actuator cable to full throttle position
against internal stop.
NEUTRAL 135–155 psi (931–1068 kPa) 135–155 psi (931–1068 kPa)
FORWARD 135–155 psi (931–1068 kPa)
Uncouple the output flange.
135–155 psi (931–1068 kPa)
Uncouple the output flange.
REVERSE 230–275 psi (1586–1896 kPa) 230–275 psi (1586–1896 kPa)
Properly adjust mechanical linkage.
PROCEDURES:
(1) Remove the temperature probe and install 0–100 psi (0–689 kPa) oil pressure gauge.
(2) Drive the vehicle until the transmission reaches fourth range.
(3) Apply the retarder, 100 percent.
(4) 100 percent apply pressure should be 50–62 psi (345–427 kPa).
(5) Release the retarder and re-apply the retarder at 50 percent.
(6) 50 percent apply pressure should be 20–32 psi (138–220 kPa).
NOTE: Retarder pressure will drop during downshift.
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