Drive Range, Seventh 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.

Drive Range - Seventh Gear is used to maximize engine efficiency and fuel economy under most driving conditions. Input signals from the transmission speed sensors (input and output), throttle position (TP) sensor, and other vehicle sensors, are used by the TCM to determine the precise moment to shift the transmission into Seventh gear. In Seventh gear, the planetary gear sets rotate as a unit (direct drive), allowing the transfer gears to provide a 1.000: 1 gear ratio to the front differential carrier (238).

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. 5-7-Reverse Clutch Assembly Applied

The 5-7-reverse clutch plates (578-582), splined to the 5-7-reverse and 6-7-8-9 clutch housing (530) and the 3-8 and 5-7-reverse clutch hub (534), are applied and drive the 3-8 and 5-7-reverse clutch hub (534).

5. 6-7-8-9 Clutch Assembly Applied

The 6-7-8-9 clutch plates (570-577), splined to the 5-7-reverse and 6-7-8-9 clutch housing (530) and the reaction carrier hub (532), are applied and drive the reaction carrier hub (532).

6. Overdrive Carrier Driving

With both the 3-8 and 5-7-reverse clutch hub (534) and the reaction carrier hub (532) driving at converter turbine speed, the overdrive carrier pinions act as wedges and provide direct drive to the overdrive internal gear (output carrier assembly) (555).

7. Input Carrier Assembly Driven

With both the input internal gear (overdrive carrier assembly) (546) and the input sun gear (551) driving at converter turbine speed, the input carrier pinions act as wedges to obtain direct drive through the input carrier assembly (552).

8. Output Carrier Assembly Driving

With both the overdrive carrier (546) and the input carrier assembly (552) driving at converter turbine speed, the output carrier assembly (555) rotates as a unit, providing direct drive to the output carrier transfer drive gear hub (502).

9. 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).

10. 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).

11. Driven Sprocket Driven

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

12. 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.