Automatic Transmission - Overhaul: Description
This is a fully automatic 4-speed unit consisting primarily of a 3-element welded torque converter and 2 compound planetary gear sets. Two multiple-disc clutches, 1 overrunning clutch, and 3 brake bands provide friction elements required to obtain desired function of planetary gear set. A hydraulic system, pressurized by a primary gear type pump and a secondary piston type pump provide working pressure required to operate friction elements and automatic controls.
On 380 Series models, to relieve load on the vehicle's service brakes on lengthy downgrades, the engine's braking effect is utilized by providing an additional shift lever position "B" (Braking). When the shift lever is placed in position "B", the solenoid valve in the transmission is energized through the switch at the shift lever. The transmission will remain in first gear independent of accelerator position. It will shift to second gear when the regular kickdown shift point is reached.