4LO Mode Power Flow

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: 4LO Mode Power Flow

Courtesy of GENERAL MOTORS CORP.

During a range shift request to 4LO, a separate cam profile, on the same shift detent lever (12), moves the high/low shift fork (13). The high/low shift fork (13) moves the high/low range sleeve (6) rearward. The high/low range sleeve (6) outer teeth disengage from the input shaft (2) high-speed teeth. The high/low range sleeve (6) outer teeth then engage in the high/low planetary carrier teeth (5). The power flow is now from the transmission (1) to the planetary teeth on the input shaft (2) to the planetary gears (3) in the carrier. Rotating the planetary gears (3), which are engaged in the annulus gear (4), rotates the planetary carrier. The planetary carrier delivers the power to the high/low range sleeve (6). The high/low range sleeve (6) then drives the rear output shaft (7), providing a 2.72:1 gear ratio reduction to the rear output shaft (7). The 2/4 wheel drive synchronizer (8) is still engaged to drive the drive sprocket (9), as in the 4HI position, providing the engine power to the rear propeller shaft (10) and to the front propeller shaft (11).