GM Service Manual Online
For 1990-2009 cars only

Manual Third - At any time, when the vehicle is driven in Forward, you can choose 3rd gear. But TCM control prevents transmission to shift to more than 3rd gear. When the shift lever shifts from Manual Fourth to Manual Third, the manual valve will move, too. The following changes will occur in the hydraulic and electrical systems:

Overdrive Clutch Apply

Manual Valve: The line pressure is sent to 32 fluid circuit of manual valve. 32 fluid is sent to the safety mode valve.

1-2 SS Valve: 1-2 SS valve is energized to allow the feed limit fluid to flow into the 1-2 signal fluid passage. 1-2 signal fluid is sent to the safety mode valve and the 3-4 shift valve.

3-4 Shift Valve: 1-2 signal fluid overcomes the 3-4 shift valve spring tension and move the 3-4 shift valve to the applied position. The operation makes D432 fluid flow into the 123 fluid circuit and drain out the direct clutch with 45 fluid.

#4 Ball Check Valve: 123 fluid goes against the #4 ball check valve and flows into 4-5 shift valve through valve bore #16.

4-5 Shift Valve: 123 fluid flows into 123 brake fluid circuit through 4-5 shift valve (333).

Low Pressure Control Valve: 123 brake fluid flows into 123 adjusting circuit through Low pressure control valve (383).

1-2 Shift Valve: 123 adjusting fluid flows into 23 adjusting circuit through 1-2 shift valve.

#9 and #11 Ball Check Valves: 23 adjusting fluid goes against the #9 and #11 ball check valves and flows through valve bore #22 and #23.

2-3 Shift Valve: 23 adjusting fluid flows into the overdrive clutch No. 1 feed fluid circuit through 2-3 shift valve.

#12 Ball Check Valve: Overdrive Clutch No. 1 feed fluid positions the #12 ball check valve against the Overdrive Clutch No. 2 feed circuit and flows into the Overdrive Clutch fluid circuit.

Direct Clutch Release

Direct Clutch: Direct clutch fluid is drained from the direct clutch piston and release direct clutch plate.

3-4 Shift Valve: Direct clutch fluid flows to the 3-4 shift valve through the valve bore #26, and drains from the valve.

Shift Accumulator

Direct Clutch Accumulator: Direct clutch fluid is also drained from the direct clutch accumulator assembly.

Accumulator fluid makes the direct clutch accumulator piston overcome the accumulator spring tension to prepare for Direct Clutch apply once again.

Manual Third - 3rd Gear, when the vehicle is driven in Overdrive - 5th Gear and the transmission clutch applies, if you choose Manual Third, then the TCC cannot release. Under normal operating conditions, the operation of TCC in Manual third - 3rd Gear is the same as in Overdrive - 3rd Gear.

Manual Third


Object Number: 819329  Size: FS