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42RLE automatic (4-speed)

The overdrive that retired the Wrangler's three-speeds

In the Wrangler TJ, the 2003 restyle retired the three-speeds and brought the four-speed 42RLE with overdrive. It's an Ultradrive adapted to rear-wheel drive: more modern, with an electronically locking converter and a tall fourth for relaxed cruising.

An Ultradrive for the Jeep

The 42RLE descends from the Ultradrive family (the front-wheel-drive 42LE), reworked to a longitudinal layout for rear-drive and 4x4 Jeeps. It backed the 4.0 straight-six in the TJ (2003–2006) and carried into the JK with the 3.8 V6 (2007–2011); it was also the Liberty KJ/KK's automatic with the 3.7. In 2012, with the 3.6 Pentastar, the JK moved to the five-speed W5A580.

Its overdrive fourth (0.69) is tall and its first (2.84) reasonably short; for off-road use on big tires it still pays to compensate with the axle ratio.

Details and maintenance

The 42RLE uses an electronically modulated converter clutch (EMCC): instead of locking all at once, it applies lockup progressively to smooth things out. That makes it more refined than the old TorqueFlites, but also more dependent on the electronics and on healthy fluid.

It doesn't have an AW-4's unbreakable reputation, but cared for it does its job. The usual: ATF+4 on schedule, good cooling if you work it, and check the sensors before blaming the transmission.

Specifications