F 250 2WD Pickup V8-7.3L DSL Turbo VIN F (1994)
Shift Modulator: Description and Operation
Fig. 7 Altitude Compensating Vacuum Diaphragm
ALTITUDE-COMPENSATED VACUUM DIAPHRAGM
The unit incorporates an evacuated bellows that is sensitive to barometric pressure. Barometric pressure decreases about one inch Hg for each
1000 feet altitude increase. The bellows decreases throttle pressure at higher altitude to make the shift feel comparable to lower altitude. The
engine power loss at high altitude is offset by a lower throttle pressure and the shifts remain smooth.
