GMC 4000 Series Service Manual page 134

rear axle to vacuum and opposite side to atmos-
phere. In "Lo" speed position, vacuum is supplied
H IG H A X LE P O SIT IO N
1 Control Cable
2 Cable Trunnion
3 Atmosphere Port
4 Speedometer Shift Port
5 Vacuum Port
G M C S E R V I C E M A N U A L
6 Atmosphere Closed
- Vacuum Open
7 Atmosphere Open
- Vacuum Closed
8 Atmosphere Open to Axle
9 Vacuum Open to Axle
Figure 5 — O p e ratin g Positions of V a cu u m Shift Control V a lve
REAR AXLE AND CONTROLS
to speedometer adapter causing rod to move inward
shifting speedometer into low ratio.
L O W A X LE PO SITIO N
10 Atmosphere Open
11 Atmosphere Closed
12 Poppet Lever
13 Operating Lever
Sec. 4A
Page 127
- Vacuum Closed
- Vacuum Open
T P M -7 5 9 1