Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Overdrive Range, First Gear (With Touch Activated Power)
2008 Pontiac Grand Prix V6-3.8LSECTION Overdrive Range, First Gear (With Touch Activated Power)
Overdrive Range, First Gear (With Touch Activated Power)
When the gear selector lever is moved to the Overdrive (D) position from the NEUTRAL (N) position the following changes occur to shift the transmission into Overdrive Range - First Gear.
Manual Valve (404)
Is moved by the gear selector lever and allows line pressure to enter the D4 passage.
Number 6 Ball Check Valve (372)
Located in the control valve body (300), blocks forward servo apply passage forcing D4 pressure to the forward servo boost valve (367), the forward servo feed orifice on the spacer plate (370). When the manual valve (404) is moved from DRIVE to PARK or NEUTRAL, the ball check valve unseats to allow for a quick exhaust of servo apply fluid and release of the forward band assembly (688).
Forward Servo Assembly (15-22)
Applies and holds the forward band (688) during all forward gear drive ranges.
Forward Band Assembly (688)
Wraps around and holds the 1-2 support outer race (687) during all forward gear drive ranges.
1-2 Shift Solenoid (SS) Valve (315A)
Energized (ON) by the PCM, high pressure in the 1-2, 3-4 signal fluid circuit holds the 12 shift valve in the downshifted position. 1-2, 3-4 signal fluid also is routed to the 3-4 shift valve, but is not effective.
2-3 Shift Solenoid (SS) Valve (315B)
Energized (ON) by the PCM, high pressure in the 2-3 signal fluid circuit holds the 2-3 and 3-4 shift valves in the downshifted position.
Input Clutch
Remains applied from NEUTRAL to DRIVE and becomes effective as the forward band applies. The input sprag holds at this time.
1-2 Support Roller Clutch
The 1-2 support roller clutch holds when the forward band is applied.
Overdrive Range, First Gear - With Touch Activated Power
Overdrive Range, First Gear - With Touch Activated Power:
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.