Differences Between 42RE and 42RH Transmissions

by Rob Wagner

Chrysler produced the 42RE and 42RH four-speed automatic transmissions. The 42RH was a medium-duty transmission, while the 42RE was a heavy-duty version of the same transmission. They featured identical gear ratios, but the 42RE used electronic components to shift gears. The 42RH used a mechanical hydraulic system. Both transmissions matched engines in Dodge Dakotas and Jeep Cherokees, among other Chrysler vehicles.

Background

The 42RE and 42RH derived from the A500 automatic transmission that was essentially a four-speed version of Chrysler’s TorqueFlite three-speed automatic. Chrysler used the transmissions mostly in rear-wheel drive Dodge trucks, vans and its Jeep lineup with engines displacing from 3.9 to 5.2 liters. The transmission family also included the 44RE, 46RE and 46RH automatic transmissions. The two transmissions were available starting in 1989. Both transmissions featured a 10.75-inch diameter torque converter.

42RE

The 42RE used an electronic governor to control the transmission’s first through third gear bands, clutches, planetary gear sets and over-running clutch system. The 42RE’s fourth gear featured an overdrive clutch, the direct clutch, over-running clutch and the planetary gear system. Only fourth gear had the overdrive component. The 42RE also came with a lock-up clutch inside the transmission’s torque converter. The 42RE version had a new valve-body transfer system not compatible with any other Chrysler four-speed automatic. Its governor body and electronic components were also different from other electronically controlled automatic transmissions. The transmission was smaller than the 42RH because it did not need the mechanical governor components and tubes.

42RH

The 42RH operated its bands, clutches and planetary gear sets via hydraulic mechanical components by applying pressure to the governor for shift speed control. It operated the same as the 46RH version that matched the engine’s Powertrain Control Module, or PCM, which adjusted the vehicle’s speed through the torque converter according to its axle ratio and tire size. The transmission also featured a transmission temperature-control system that worked in tandem with the radiator temperature sensor to keep the transmission cool.

Gear Ratios

The 42RE and 42RH had the same gear ratios: 2.74-to-1 for first, 1.54-to-1 for second, direct 1.00-to-1 for third and 0.69-to-1 for fourth.

Applications

The two transmissions transmitted power from the engine to vehicles with a gross vehicle weight rating of 7,800 pounds or less. The transmissions came in the 1989 to 2001 Dodge Ram two-wheel drive 150 and 1500 pickups equipped with a V-6 or V-8 engine and the 1989 to 2003 Dodge Ram Van B150 and B250 vans with a V-6 or V-8. They also matched the 1989 to 2003 Dodge Dakotas equipped with the V-6, the 1993 to 2004 Jeep Grand Cherokee equipped with a 4-liter in-line six-cylinder engine and the 1996 to 1998 Jeep Grand Cherokee equipped with a 5.2-liter V-8. The 42RE, but not the 42RH, matched the NP242 transfer case for the Jeep Cherokee and Wagoneer SUVs, Comanche pickup truck and the Liberty.

About the Author

Rob Wagner is a journalist with over 35 years experience reporting and editing for newspapers and magazines. His experience ranges from legal affairs reporting to covering the Middle East. He served stints as a newspaper and magazine editor in Saudi Arabia and the United Arab Emirates. Wagner attended California State University, Los Angeles, and has a degree in journalism.

Photo Credits

  • photo_camera Scott Olson/Getty Images News/Getty Images