How A Mercedes-Built Manual Transmission Became The Jeep Wrangler's First Six-Speed

The infamous Daimler-Chrysler "merger of equals" only lasted nine years, from 1998 to 2007, and never quite lived up to its billing. Instead, at least on the Chrysler side of the ledger, drivers were mostly treated to Mercedes-Benz hand-me-downs like the R170 platform. It first underpinned the MB SLK before finding a second life beneath the Chrysler Crossfire — and under the occasional project car like the Mercedes SLKarmann Ghia. Meanwhile, Jeep fanatics may know that the brand's very first six-speed manual transmission came from the German parts bin, too

The NSG370 gearbox actually had been used earlier in the Crossfire, and it would be used in Jeep models like the Liberty, too. But the transmission was manufactured at the Daimler plant in Stuttgart, Germany. The "NSG" stood for "Neues Schaltgetriebe," which translates into something like "new manual-shifting transmission." And to be clear, not only was the NSG370 the first six-speed manual for the Wrangler, it was the first six-speed gearbox of any kind ever featured by the nameplate.

That's because the Wrangler seems to have skipped the six-speed automatic entirely. The brand jumped from the five-speed slushbox for the 2012-2017 models directly to the eight-speed unit introduced in the 2018 JL Wrangler. Note that the Wrangler is still out there saving the manuals with a six-speed transmission. However, the debut of the JL series also saw the debut of a new manual transmission source, Aisin — which was actually an old source. Aisin had made the Wrangler's five-speed manual before it was replaced by the six-cog NSG370.

The NSG370 launched as part of the upgrades for the 2005 Wrangler, including the Wrangler Unlimited. Mechanical highlights started with triple-cone synchronization for first and second gears and double-cone synchronization for third and fourth gears, taking advantage of synchromesh technology to make changing gears smoother and easier. The fifth and sixth gears had a single cone for synchronizing the shifting process. As for the physical gears themselves, they were hard-finished to help reduce noise, vibration, and harshness (NVH).

The gearbox further boasted a multi-rail shift system made from steel, for extra strength, and it relied on an aluminum case to lower its weight without sacrificing stiffness. For off-road action, the transmission was upgraded with a steep first-gear ratio of 4.46:1. As a result, when the Wrangler was specced with its 4.10:1 axle ratio and 4.0:1 transfer case, owners could enjoy a crawl ratio of 73:1. The 2026 Wrangler Rubicon, for comparison, can manage a 100:1 crawl ratio. Higher is better since the numbers basically represent how many engine revolutions are required to rotate the wheels a single time. In other words, you can gain access to more torque without worrying about increasing your speed too much and getting out of control.

At the other end of the spectrum, the sixth gear in the NSG370 is an overdrive for efficient highway cruising with a ratio of 0.84:1. Of course, "efficient" in this case was relative. The '05 Wrangler's best EPA ratings, with the manual transmission and base 2.4-liter four-cylinder engine, were the same 16 mpg city/19 mpg highway/17 mpg combined as those for the similarly equipped 2004 model with one fewer gear.