1991 model year adapted their own engine control electronics to replace the original Renix systems used with the 2.5 L and 4.0 L engines. Power and torque in both engines improved as a result, with the four-cylinder having an additional 9 hp and 8 lb⋅ft and the six-cylinder improving by 1 lb⋅ft and 13 hp. The 4.0 L was badged "High Output" thereafter. As a result of the power improvements the Aisin-Warner automatic transmission's output shaft was changed from 21 splines to 23, and the "Power-Comfort" switch was deleted. The four-cylinder was no longer available with the automatic in 1991 and 1992. During the production life of the Comanche six different transmissions were offered, manufactured by Aisin, Chrysler, and Peugeot. Chrysler provided the aforementioned TorqueFlite 904 three-speed automatic in 1986 models. In addition to the aforementioned 30-40LE four-speed automatic Aisin also provided the AX-4 (four-speed), AX-5 and AX-15 (five-speed overdrive) manual transmissions. The AX-15 was phased in midway through the 1989 model year to replace the Peugeot BA10/5 five-speed that had been used behind the 4.0 L engine from its introduction in 1987. Comanches were available in either two or four-wheel-drive, with solid axles front and rear (two-wheel-drive Comanches used a simple beam axle with otherwise the same front suspension as four-wheel-drive models). Transfer cases were built by New Process Gear, and the Comanche was available with either part-time "Command-Trac" or full-time "Selec-Trac" systems. In 1986 Command-Trac transfer cases were model NP207 and Selec-Trac were NP228, both with a 2.61:1 low gear ratios. In 1987 the NP207 was replaced with the NP231 and NP228 was replaced with the NP242, both with 2.72:1 low gears. These remained the same through the rest of the Comanche's production. Engines Transmissions Trims By model year availability: 1986 - Custom - The most basic Comanche trim that could be ordered. 1986 - X - One of the more "basic" trims of the Comanche. 1986 - XLS - A "step-up" version of the more "basic" Comanche trims. 1987-1992 - Base (SporTruck) - Became the most basic trim of the Comanche after 1986. 1988- Olympic Edition - Based on the Pioneer trim to commemorate the 1988 Summer Olympics and Team U.S.A. . 1987-1988 - Chief - Added more standard equipment to the base-level Comanche trims. 1987-1990 - Laredo - The top-of-the-line and most "up-level" trim on the Comanche. 1987-1992 - Pioneer - A "step-up" version of the