Regular-wheelbase models comes standard with a naturally aspirated 2.5-liter 4-cylinder and 3-speed automatic transmission. It provides 100 horsepower at 4800 rpm and 135 pound-feet of torque at 2800 rpm. The optional engine is a 3.0-liter V6 that provides 142 horsepower at 5000 rpm and 173 pound-feet of torque at 2400 rpm. A 3.3-liter V6 is standard on Grand Voyagers and optional on regular-length SE and LE models. Manual transmissions were dropped for 1991, then returned as the standard gearbox for base-model Voyagers equipped with 2.5-cylinder engines for 1992-94. The manual transmission is then dropped again for 1995. The 4-cylinder Voyagers come with a 3-speed automatic in 1991 and 1995; in short-wheelbase models, the V6 engines are available with either a 3- or 4-speed automatic, while all Grand Voyagers have the 4-speed gearbox. The permanently engaged 4-wheel-drive models require the 3.3-liter V6. For 1992, the Grand Voyager is available with a lower-cost, 142-horsepower 3.0-liter V6 and 3-speed automatic in place of the standard 150-horsepower 3.3-liter V6 with its 4-speed automatic. For 1994, a 3.8-liter V6 is a new option for Grand Voyager LE models. It delivers 162 horsepower at 4400 rpm and 213 pounds-feet of torque at 3600 rpm. Horsepower and torque for the 3.3-liter V6 that comes standard on the Grand SE have been upgraded as well, to produce 162 at 4800 rpm and 194 pound-feet of torque at 3600 rpm. For 1994, an overdrive lock-out switch comes on all 4-speed automatics paired with Chrysler's three V6 engines. For 1995, a 3.3-liter V6 is engineered to run on compressed natural gas and comes packaged in a new CNG version of the Plymouth Voyager. The CNG engine produces 135 horsepower.