GMC's version of the Chevrolet Silverado gets no major changes for 2006 as both trucks await redesigned replacements for 2007. This report covers the half-ton Sierra 1500 and 1500HD models. They come in regular-, extended-, and Crew Cab versions. Extendeds have rear-hinged back doors that don't open independently of the fronts. Front seating is via a bench or buckets. Extendeds and Crews include a three-person rear bench seat. Regulars and extendeds offer 6.6- and 8-ft cargo beds. For '06, extendeds are available with the Crew Cab's 5.8-ft bed.

Trim levels ascend from Work to Denali Crew Cab. Denali has all-wheel drive without low-range gearing. Other Sierras are available with rear-wheel drive or one of two 4WD systems. The basic 4WD system should not be left engaged on dry pavement, GM's Autotrac can. Both include low-range gearing. Engine choices range from a 195-hp V6 to a 345-hp V8, depending on model and option selection. Same for available manual and automatic transmissions.

Sierra is also available as a Hybrid model. It's a 6.5-ft-bed extended cab with a V8 and 2WD or 4WD. This uses an electric motor to provide 120-volt power for electrical accessories. However, the electric motor does not propel the vehicle. Its batteries are charged by the gas engine; no plug-in charging is necessary. Sierra's performance and accommodations mirror those of comparable Silverados.