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upshifted to high range, a forced downshift can be made by
moving the manual linkage into low range.
CAUTION: Do not force a downshift at speeds above
normal "through detent upshifts" speed. See the Power
glide shift point chart in the appropriate Chassis Service
Manual for specific vehicle speeds.
Since the transmission has already upshifted to high range,
governor pressure holds the low-drive shift valve in the full
right position, the high clutch circuit exhaust port is blocked.
Thus, to shift the transmission to manual low, the normal low
range circuits are charged and the high clutch oil exhausts at
the manual valve (fig. 25PG). As this pressure exhausts, the
transmission downshifts to low range.
Fig. 25PG-Downshift to Manual Low
The vacuum modulator valve receives mainline pressure
through the normal passage and through the exhaust passage.
This prevents the modulator valve from regulating and applies
full mainline pressure to the booster valve. This action causes
mainline pressure to be regulated at a higher value. The in
creased mainline pressure offsets the higher torque reactions
associated with manual low range.
"D" To Manual Low Downshift
Reverse Circuit
With selector lever in the reverse or "R" position, the
manual valve directs mainline pressure only to the reverse cir
cuit. The high clutch and low servo circuits are all open to
exhaust at the manual valve. Pressure leaving the manual valve
and entering the reverse circuits is fed to the reverse clutch and
to the booster valve (fig. 26PG). The combined pressure of
modulator pressure on one spool, and mainline between the
spools causes the pressure regulator to increase mainline
operating pressure to its maximum.
Fig. 26PG-Reverse Circuits
