Not many motor-vehicle companies can claim to have started production with military utility vehicles. According to Rola, a new- and used-car information portal, Jeep of North America is the oldest off-road vehicle manufacturer, and has been producing civilian Jeeps, or Cjs, since the mid 1940s. The Jeep YJ is a late 1980s to early 1990s civilian-model vehicle, most commonly referred to as a Wrangler.
The 2.5-liter YJ engine was a basic 150 cubic-inch AMC motor, commonly used in many Wranglers and civilian Jeeps. From 1987 through 1990, the engine was configured with an output of about 117 horsepower and 135 foot pounds of torque. The engine type was a throttle-body injection, which was a standard carburetor design. Later models of the YJ 2.5L motor received a boost in power, giving an approximate output of 123 horsepower and 139 foot pounds of torque. The main difference between the two engines was not the size, but how fuel reached the engine. From 1991 to 1995, the 2.5-liter engine was a multi-port injection, unlike a carburetor-style engine that injects fuel in a centralized location. This has become the standard method for fuel injection in automobiles, allowing for increased fuel efficiency.
Throughout its production, the 2.5L Jeep YJ used an Aisin-Warner AX5 5-speed, manual transmission. First gear ratio was 3.93:1 from 1987 to 1995, giving the YJ power at low revolutions per minute for acceleration. The NP231 “Command Trac” Transfer Case from Novak was responsible for on- and off-road shifting capabilities.
Since the YJ was a four-wheel drive vehicle, front and rear axles were manufactured by the off-road specialist, Dana Holding Corporation. The front axle from 1987 to 1995 was a Dana 30, while the rear axle was the Dana 35. Until 1989, the rear axle housed 10-inch drums, while in 1990, the 9-inch drum was introduced and production continued.
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