Last year, GMC upgraded horsepower and torque for the 4.8-liter and 5.3-liter V8s. For 2001, the V6 and all three V8s have received further refinements, enhancing economy and durability while reducing maintenance requirements. But you can bet that the V8s will be sold in much higher volumes than the V6s.Similarly, while a five-speed manual is available in basic SLs, we expect the automatic option will be far more popular. The 4L60 and 4L65 four-speed automatics feature a delayed upshift when switched into the tow/haul mode, improving performance while helping the gearbox keep its cool.
All 2WD models with V8s and automatic transmissions can now be ordered with electronic traction assist.
Optional Autotrac four-wheel-drive combines a conventional, truck-style two-speed transfer case with electronic controls. This system allows the driver to lock the axle speeds together in low range for maximum off-road traction; or to select an automatic mode that sends power to the wheels with the best grip whenever the system detects wheel slip.
All Sierras are built on the stiffest and lightest truck frame General Motors has ever produced.