Automatic Transaxle - Downshift System: Overview

9216chevy04

Number: 91-122-7A

Section: 7A

Date: November 1990

Corporate Bulletin No.: 037116


Subject: AUTOMATIC TRANSAXLE DOWNSHIFT SYSTEM


Model and Year: 1990-91 GEO STORM


TO: ALL CHEVROLET DEALERS

Base model GEO Storm vehicles equipped with automatic transaxles incorporate a switch and a solenoid (rather than a kickdown cable) for the purpose of downshifting during hard acceleration. These components have not, as yet, been covered in any of the existing GEO Storm service publications. Therefore, this bulletin has been written as an addition to Section 7A-1 of the 1990 and 1991 GEO Storm Service Manuals (ST371-90 and ST371- 91).

AUTOMATIC TRANSAXLE DOWN SHIFT SYSTEM

GENERAL DESCRIPTION





All 1990 and 1991 GEO Storms, equipped with the KF400 three speed automatic transaxle, incorporate an automatic transaxle downshift system. This system consists of fuse C-11, a kickdown switch, a kickdown solenoid and a kickdown valve. Fuse C-11 is located in the fuse block, the kickdown switch is attached to the accelerator pedal bracket, the kickdown solenoid is screwed into the transaxle and kickdown valve is integral to the transaxle.


During cruise conditions, when throttle angle is changed sufficiently to cause a 3-2 downshift (or a 2-1 downshift), the accelerator pedal strikes the plunger on the kickdown switch. When the plunger is pressed down, the switch closes and applies battery voltage through fuse C-11 and the kickdown switch to the kickdown solenoid. When battery voltage is applied, the kickdown solenoid energizes and opens the kickdown valve in the transaxle. With the kickdown valve opened, hydraulic pressure is rerouted to either the 2nd-3rd or 1st-2nd shift valve, causing the appropriate downshift to occur.