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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1028 (Transfer Case - NVG 261-NP2) >> Description and Operation >> Transfer Case Description and Operation >> 4HI Mode Power Flow

4HI 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: 4HI Mode Power Flow
GM837771Courtesy of GENERAL MOTORS CORP.

In the 4HI mode, the engine power from the transmission (1) is delivered to the input shaft (2). The engagement teeth on the inside of the input shaft (2) are engaged to the outer teeth on the high/low range sleeve (3). The high/low range sleeve (3) is slipped splined to the rear output shaft (4). During a shift mode from 2HI to 4HI the cam profile on the shift detent lever (14) pushes the 2/4 wheel drive mode shift fork (9) and the synchronizer sleeve. The sleeve, engaging the synchronizer (5) equalizes the front propeller shaft (12) and rear propeller shaft (7) speeds. Then the sleeve engages to the 2/4 wheel drive synchronizer gear (8), which is splined to the drive sprocket (6). The engine power flow for driving the front propeller shaft (12), now travels from the rear output shaft (4) to the synchronizer hub, which is splined to the rear output shaft (4). The power flows from the synchronizer hub to the sleeve and then to 2/4 wheel drive synchronizer gear (8). The power flow is transmitted by a chain (10) to the driven sprocket on the front output shaft (11) and to the front propeller shaft (12). The front and rear propeller shafts are being driven at equal RPMs, therefore giving a four wheel drive mode. This mode should only be used for extra traction. Using this mode on dry pavement causes tire scuffing when turning.