The Oldsmobile Bravada, a four-door SUV, was offered with four-wheel drive during all model years. Three generations of the Bravada were produced. Each generation used a different series of transfer cases.
1991 to 1994 Bravada
All first generation Bravadas -- 1991 to 1994 -- were produced with Smart-Trak all-wheel drive. The Borg Warner 4472C (BW4472C) transfer case is utilized in these trucks. Both axles remain engaged. The viscous clutch of the BW4472C compensates for the varying speed of the front and rear axles, allowing the four-wheel-drive to stay engaged at all times without damage, even on dry pavement. Its planetary gear transmits torque at a ratio of 35% front and 65% rear and directs power to the wheels with traction whenever slip is detected. This is a two-piece case, and it is chain-driven.
1996 to 2001 Bravada
Second generation Bravadas were equipped with either the BW4472 or the New Process Gear 136 transfer case. The second generation Bravada began production in 1996 -- there were no Bravadas produced in 1995. After 1998, Bravadas with Smart-Trak use the New Process Gear 136 transfer case. This is an "active on demand" computer-controlled transfer case. The vehicle normally uses rear-wheel drive, and when wheel slippage is detected, an electrically actuated clutch engages the front axle. No driver input is needed to engage the all-wheel-drive system -- the vehicle has sensors to detect the speed of each axle.
2002 to 2004 Bravada
The third generation Bravada, built on the new GMT360 platform, had more drive choices for the buyer. All-wheel-drive Bravadas use the New Process Gear 126, a slightly smaller, but similar computer-controlled transfer case than the NP136 used in prior years. It functions the same way as the NP136. Other Bravadas use one of the two-speed New Process Gear transfer cases -- the NP226, NP236 or NP246. This setup allows the driver to operate the vehicle in rear-wheel drive only, in computer-controlled all-wheel drive or in driver-activated four-wheel drive. The driver may select between the 4HI, 2HI and 4LO modes using an electronic switch on the dashboard. The 2002 to 2004 Bravada could also be ordered as a rear-wheel drive vehicle without four-wheel drive capability.
Transfer Case Replacement
According to Gears magazine, there are numerous variations of most transfer cases, even when the model number is the same. The same transfer case may have been engineered differently to fit in GM, Chrysler and Ford vehicles. When selecting a replacement transfer case, it is important to check all components for a match, including the shifter pattern and input spline count.
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