Drive Range, First Gear (Mechanical Powerflow): Notes

WARNING: This page is about a different car, the 2020 Buick Regal and 2019 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.

In Drive Range (D) - First Gear, torque from the engine is multiplied through the torque converter and transmission gear sets to the vehicle's drive axles. The planetary gear sets operate in reduction to achieve a First gear starting ratio of 4.689: 1.

1. Power From The Engine

Torque from the engine is transferred to the transmission through the engine flywheel which is bolted to the torque converter assembly (14).

2. Turbine Shaft Driven

As the torque converter turbine rotates, the 5-7-reverse and 6-7-8-9 clutch housing (530) and the turbine shaft (547) which is splined to the torque converter turbine, is also forced to rotate at turbine speed.

3. Input Sun Gear Driving

The input sun gear (551), which is splined to the turbine shaft (547), drives the input carrier assembly (552) pinion gears.

4. Input Carrier Assembly Driven

The input carrier assembly pinions walk around the input internal gear (overdrive carrier) (546) and drive the input carrier assembly (552).

5. 1-2-3-4-5-6 Clutch Assembly Applied

The 1-2-3-4-5-6 clutch plates (591-600), splined to the output sun gear (522) and the 1-reverse and 1-2-3-4-5-6 clutch piston housing (590), are applied and hold the output sun gear (522) stationary.

6. Output Sun Gear Held

With the 1-2-3-4-5-6 clutch applied, the output sun gear (522) is held stationary to the 1-reverse and 1-2-3-4-5-6 clutch piston housing (590).

7. Output Carrier Assembly Driven

The output internal gear (input carrier assembly) (552) drives the output carrier assembly pinions, which then drive the output carrier assembly (555) around the stationary output sun gear (522).

8. 1-reverse and 1-2-3-4-5-6 clutch piston Holding

The input carrier assembly (552) pinion gears attempt to drive the overdrive carrier (546) in the direction opposite of engine rotation, but the carrier is held stationary by the 1-reverse and 1-2-3-4-5-6 clutch piston housing (590). When the throttle is released, however, the 1-reverse and 1-2-3-4-5-6 clutch piston housing (590) will overrun, allowing the vehicle to coast, at least briefly, until the TCM determines that engine braking is required. At that time, the 1-reverse and 1-2-3-4-5-6 clutch piston will apply and hold the 1-reverse and 1-2-3-4-5-6 clutch piston housing inner race.

9. Overdrive Carrier Held

The overdrive carrier (546) is held by the 1- Reverse and 1-2-3-4-5-6 Clutch Piston housing (590).

10. Output Carrier Transfer Drive Gear Hub Driven

The output carrier transfer drive gear hub (502) is splined to, and driven by, the output carrier assembly (555).

11. Drive Sprocket Driving

The drive sprocket (234), splined to and driven by the output carrier transfer drive gear hub (502), drives the drive link (233) which drives the driven sprocket (241).

12. Driven Sprocket Driven

The driven sprocket (241), driven by the drive link (233), is splined to the front differential carrier sun gear (240).

13. Front Differential Carrier Sun Gear Driving

The front differential carrier sun gear (240), is in mesh with, and drives, the front differential carrier (238), thus transferring power to the front differential carrier and to the drive axles.