GM S10/S15/Sonoma Pick-Ups 1982-1993 Repair Manual



An identification tag, which is usually attached to the rear half of the case (lower portion of case on Borg Warner model), gives the model number, low range reduction ratio and assembly number. Most vehicles covered by this manual use one of two units: the New Process 207 and the New Process 231. Early model vehicles equipped with a floor mounted transfer case shifter are equipped with the 207, while late model vehicles with the floor shift are equipped with the 231. Some later model vehicles covered by this manual (1991-93) may be equipped with an electronic shift transfer case, the New Process 233. The MFI-Turbo was equipped with a Borg Warner 4472 transfer case.

The Model 207 transfer case is an aluminum case, chain drive, 4 position unit providing 4wd High and Low ranges, a 2wd High range and a Neutral position. The 207 is a part-time 4wd unit. Range positions are selected by a floor mounted shift lever. Dexron® II automatic transmission fluid, or equivalent, is usually the recommended lubricant for this unit, though some models may use SAE 80W or SAE-80W-90 GL5. Be sure to check your owners manual to be certain if Dexron®II is correct for your model.

The Model 231 is a part-time transfer case with a built in low range gear reduction system. A front axle disconnect mechanism is used for 2-wheel drive operation. The 231 has three operating ranges - 2-wheel drive High and 4-wheel drive High and Low, plus Neutral. The 4-wheel drive operating ranges are undifferentiated. Dexron® II automatic transmission fluid, or equivalent, is used as a lubricant.

The Model 233 is an electronic shift transfer case that has 3 modes of operation: 2wd range, 4wd High, and 4wd Low. Gear reduction for low range is provided by a planetary gear set. The floor mounted shifter has been replaced by a dash mounted switch for these units.

The Borg Warner 4472 transfer case is a 2-piece aluminum case, chain driven, viscous clutch type transfer case. This produces a system in which all wheel drive is engaged all of the time. Torque is transmitted through a planetary gear set which distributes torque at a ratio of 1 / 3 front and 2 / 3 rear.