The 42RLE transmission is a true testament to American engineering. This advanced, 4-speed transmission was manufactured by the Chrysler car company. Commonly associated with different Jeep Wrangler, the 42RLE automatic transmission is also known as the Chrysler 42RLE, Ultradrive, or A606 transmission. In addition to being used for the Jeep Wrangler, the 42RLE was used in the Jeep Liberty, compatible for 2003 to 2006 TJ/TJ Jeep Wranglers, 2007 to 2013 Jeep JK Wranglers, the Dodge Charger, Ram 1500, and Dodge Challenger. Predecessor and associated transmissions of the 42RLE include the 41TE/A604, 42LE/A606, 40TE, 41AE, 62TE, and 40TES/41TES.

The 42RLE is based on the older 42LE and was typically found in FWD domestic cars. In these vehicles, the transmission was mounted sideways. It wasn't until the Original Equipment Manufacturer 42LE was modified in 2003 and started being utilized in RWD traditional applications that it became the 42RLE. Once modified, the transmission was used in the newly-minted Jeep Liberty — at the time. Let it be known that when it comes to stock transfer case compatibility depends on the make and model of the vehicle it was in; However, the most common transfer cases to be paired with this transmission from the factory are the NV144D, NP231 (NP231J), NP241 (NP241J), and the NV244.

The modification was made by removing the transfer chain, removing the integral differential, and altering the transmission case. These instrumental changes were performed at the factory to ensure superior performance and to route power flow through the rear of the transmission.

One of the most fascinating advancements of the 42RLE transmission was the introduction of the Ultradrive. As one of the first electronically controlled automatics, the Ultradrive technology included adaptive shifting memory that works to learn the driver's habits controlled by the Transmission Control Module (TCM). At the same time, the 42RLE featured an Electronically Modulated Converter Clutch (EMCC) that is housed within the automatic torque converter. This feature is engineered to serve as a shock absorber for brash and harsh shifting.

Unfortunately, the Ultradrive feature failed due to significant unreliability. The problems associated with the Ultradrive can largely be attributed to the rush to get it to market —namely, labeling issues. Even though the fluid dipstick and owner's manual suggested the use of Dexron transmission fluid, this fluid caused the transmission to malfunction. And when owners no longer used the fluid, those issues ceased to exist shortly after.

Another problem associated with the 42RLE transmission was that owners assumed the unit was malfunctioning when it was actually the limp mode feature. Whenever the computer received an incorrect reading from one of the sensors, the transmission would be forced into second gear only. Working as designed, this innovation would enable the vehicle to “limp" to the closest repair shop, while mitigating further damage to the transmission.

The issue caused owners to assume the transmission failed, which often led to premature replacement of the powertrain. And if the problem did originate from the second gear, the limp mode would completely disable the transmission and not allow it to move at all.