Pontiac tempest 1968 Service Manual page 538

T W O SPEED A U T O M A T I C TRANSMISSION
7F-37
Co Check modulator valve and bore in case for
freedom of movement.
d. Check freedom of boost valve in front pump
regulator.
2. Valve body bolts loose. Torque specification Is
10 l b . f t .
3. Low o i l level.
PRESSURE CHECKS
Pressure checks are a ^sefal part of trouble diag­
nosis. The pressure tap for checking mainline pres­
sure is located above the o i l pan r a i l on the right
side of the transmission and to the rear of the low
servo.
Tests can be made without driving the vehicle by
simply raising rear wheels 3-5 inches from floor on
jack stands. With pressure gauge installed, perform
following preliminary steps:
1. Establish pressure gauge indicator needle rest
position at zero pressure.
2. Thoroughly warm up transmission.
3. Check transmission o i l level.
4. Make sure vacuum line connections are tight.
5. Check linkage adjustment.
Mainline pressure w i l l vary from one transmission
to another but following statements apply in general.
Line pressure should increase as engine mani­
fold vacuum decreases, at a constant speed.
Line pressure should decrease as car speed
increases, at a constant engine manifold vac­
uum (for example, about 13 psi between 40-60
mph).
Reverse pressure should be about 85 psi at idle
to over 200 psi at stall (wide open throttle with
brakes on).
NOTE: Do not operate at wide open throttle with
brakes on longer than it is necessary to obtain a
gauge reading.
MAXIMUM LINE PRESSURE
Maximum line pressure checks are to be made i n
garage bay with vacuum modulator line disconnected
and plugged and with engine speed set at 1000 rpm.
See figure 7F-111 for pressures.
MINIMUM LINE PRESSURE
Minimum line pressure checks are to be made
while road testing the car with the vacuum modulator
line connected. Checks are to be made as follows:
1. Park, Neutral and Drive - 56 psi. Drive -
coast at 20-40 mph with foot off throttle. Neutral
and Park - check at 1000 r p m .
2. Low - 92 psi; coast at 20-40 mph with foot off
throttle.
3. Reverse - 84 psi; coast with foot off throttle.
MODEL
L A , L B ,
L F , LG LD, L H MA, MB MC
Barometric
D & L
D & L
D & L
D & L
Altitude Pressure ± 4 psi ± 4 psi ± 4 psi ± 4 psi
Sea Level 29.92
155 147 165 163
2,000 f t . 27.82
147 140
157 155
5,000 f t . 24.89 134
128 144
144
Reverse Line Pressure should exceed Drive Pressure by at least 60 psi
Fig. 7F-111 Maximum Line Pressure