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NSG370 manual (6-speed)

The Wrangler's Mercedes-sourced six-speed

When DaimlerChrysler wanted to give the Wrangler a more modern manual, it reached for a Mercedes-sourced box: the six-speed NSG370. It was Jeep's first six-speed manual. It added an extra ratio for relaxed highway cruising without giving up the low gears for off-road.

From the AX-15 to six speeds

The NSG370 was built by Mercedes-Benz at its Stuttgart transmission plant, and it replaced the old five-speed manuals (like the AX-15 and the NV3550) in the Wrangler TJ from 2005, and was the JK's only manual throughout its life (2007–2018). Fifth is direct (1:1) and the tall sixth drops the revs on the highway; the well-reduced first (4.46) still works for the mud.

In the JK it paired with both the 3.8 and the 3.6 Pentastar, the purists' choice over the automatics. Outside the Wrangler it also showed up in the Liberty KJ/KK and even the Dodge Nitro and Chrysler Crossfire.

Maintenance and details

One important NSG370 detail: it calls for a specific Chrysler fluid (MS-9224), because its brass synchros won't tolerate just any oil. Using the wrong lubricant is one of the most common causes of hard shifts and noise. With the right fluid and up to temperature, it's a precise box with a good throw.

It's not indestructible: pushed with very large tires and abrupt downshifts it can suffer in the lower-gear synchros. But for mixed use —highway and moderate off-road— it's a modern, pleasant manual, with the bonus of that sixth gear the old five-speeds never had.

Specifications