General Motors' Ypsilanti Transmission Operations is producing a new variant of its Hydra-Matic rear-wheel-drive six-speed transmission. The new 6L90 six-speed electronically controlled automatic transmission is standard in the all new 2007 GMC Sierra and Chevrolet Silverado heavy-duty pickups.
Advantages of the new 6L90 transmission include improved fuel economy, performance and handling:
• The 6L90 transmission has a wide overall ratio spread of 6.04, compared to 3.31 in the previous 4L80 used in the heavy-duty pickup trucks. This allows a "steep" 4.03 first gear, which provides an improved performance launch feel.
• With this wide ratio spread, there are smaller steps between the gears, optimizing the gear ratio for towing, providing good shift quality, and maximized acceleration and fuel economy.
• With two overdrive gears - fifth and sixth - engine rpm is reduced by approximately 19 percent at 60 mph - a reduction of about 400 rpm. A lower engine speed reduces engine wear and improves fuel economy. Engine noise is also lower during cruising.
• The 6L90 has the capability for Driver Shift Control (Tap Up/Tap Down), Tow/Haul Mode, Auto Grade braking and uses DEXRON VI premium fluid, which has been validated to improve durability and provide more consistent shift performance in extreme conditions.
The GM Ypsilanti Transmission Operations (YTO) has produced nearly 200,000 transmissions since it opened in January 2003. The plant employs 500 people. YTO currently produces the 6L80 six-speed transmission for the Cadillac Escalade ESV and EXT; the Cadillac XLR and XLR-V; the Cadillac STS-V; the GMC Yukon Denali; and the Chevrolet Corvette. It also produces the 6L50 six-speed transmission for the Cadillac STS and the SRX.