A new 118-horsepower, 2.2-liter 4-cylinder served as base engine, with 5-speed manual shift or electronic 4-speed automatic. That engine was revised in '98 with 2 more hosepower. A 165-horsepower, 4.3-liter V6 was optional (standard with 4WD), and any model might have the 195-horsepower "enhanced" version. With the ZR2 option, that engine could only have manual shift. Available 4WD was again an on-demand, part-time Insta-Trac setup. Automatic-locking hubs were standard and an electronic transfer case was available, using pushbuttons instead of a floor-mounted lever. Output of the regular V6 engine dropped by 10 horsepower (to 155) for 1995, while the enhanced engine dipped to 191 horsepower. Automatic was mandatory on SS models with the 191-horsepower engine. For 1996, both V6 engines were modified internally, becoming part of the Vortec family. The standard V6 now developed 180 horsepower (170 when installed in 2WD trucks). The step-up version was rated 190 horsepower (180 with 2WD).