Pontiac FIREBIRD 1972 Service Manual page 1041

TURBO HYDRA-MATIC (M-38) TRANSMISSION 7G-3
1
With vacuum l i n e CONNECTED and pressure gage installed:
I
Selector Lever I n
-
I
Drive
-
1st Gear (0 to WOT)
. . . . . . . . . . . . .
-
2nd Gear (0 to WOT)
. . . . . . . . . . . . .
-
3rd Gear (Coast
@
30 mph)
. . . . . . . . . .
Super
(Coast
@
30 mph)
. . . . . . . . . .
Low
(Coast
@
30 mph)
. . . . . . . . . .
Rgverse (0 to WOT)
. . . . . . . . . . . . .
WOT
=
Wide Open Throttle Pressures are approximate (*5 psi)
Fig. 7G-2 Oil Pressure Check
-
Road or Normal Operating Conditions
1st GEAR-OVERRUN BRAKING
With selector lever in SUPER range and, with vehicle
speed at approximately 30 rnph at constant throttle, move
selector lever to LOW range. Transmission should down-
shift to first gear. An increase in engine rpm and an engine
braking effect should be noted. Line pressure should re-
main constant (approximately 85 psi).
OIL PRESSURE CHECKS
ROAD OR NORMAL OPERATING CONDITIONS
While road testing vehicle with the transmission oil pres-
sure gage attached and the vacuum modulator tube CON-
NECTED, the transmission line pressures should check
approximately as shown in Fig. 7G-2.
VEHICLE COASTING AT 25 MPH
While vehicle is coasting at 25 rnph (foot off throttle),
transmission oil pressure gage attached and the vacuum
modulator tube CONNECTED, the transmission line
pressures should check approximately as shown in Fig.
7G-3.
VEHICLE STATIONARY AND ENGINE AT 1200
RPM
While vehicle is stationary (service brake on), engine
speed set to 1200 rpm, with transmission oil pressure gage
attached and the vacuum modulator tube DISCON-
NECTED, the transmission line pressure should check
approximately as shown in Fig. 7G-4.
GOVERNOR PRESSURE CHECK
1. With car on hoist (rear wheels off ground), discon-
nect the vacuum line to the modulator, install a line
pressure gauge to the transmission and a tachometer
to the engine.
Vehicle coasting 0 2 5 mph, Vacuum line CONNECTED,
pressure gage installed and foot o f f throttle:
Fig. 7G-3 Oil Pressure Check
-
Vehicle Coasting
Selector Lever I n
-
Neutral
Drive
Super
Low
2. Start engine, keep foot off brake, move selector lever
to DRIVE range and check line pressure with engine
speed at 1,000 rpm's.
Pressure
(PSI)
60
60
85
85
3. Slowly increase engine speed to 3,000 rpm's and de-
termine if a line pressure drop occurs (7 psi or more).
Pressures are approximate
(*
5 psi)
4. If no pressure drop takes place:
a. Inspect governor
(1) Stuck governor valve.
(2) Stuck governor weight.
(3) Restricted orifice in governor valve.
b. Check governor feed system
(1) Plugged or restricted screen in control valve
assembly.
(2) Restrictions in feed line.
(3) Scored governor bore.