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Does Ram need lower axle ratios?

by David Zatz on

Across various Internet forums, truck buyers have been commenting that the new Ram 1500 Hemi, with the eight-speed automatic, is only available at many dealers with the 3.21:1 ratio. Many buyers are used to ordering the 3.92 ratio.

There is more to the story, which explains why the 3.21 is a popular choice — and why a 3.92 might not be desirable for most buyers.

The six-speed Chrysler automatic, which can trace its roots right down to the legendary TorqueFlite three-speeds, still has a higher ratio. The reason for the change is because the new eight-speed has a very low first gear — with a 4.71:1 ratio (lower gears have higher numbers). The wide range of the eight speed lets it have a 0.70:1 top gear (gearing has been changed for the Ram eight-speeds).

Meanwhile, the six-speed 65RFE has a 3.00:1 first gear ratio (and the same top gear of 0.67). The heavier duty versions, the 66RFE and 68RFE, have lower first gears (3.23:1), and even taller top gears (6.25:1).

If one puts together that low first gear, one finds that the overall ratio, including both transmission and axle, ends up at 12.30:1 with the six-speed automatic and a 4.10 axle. With the 3.92:1 axle, the six-speed automatic can only muster a multiplication of 11.76. By contrast, the eight-speed is much lower even with the 3.21 ratio — at 15.12.

The wide range delivers better fuel economy and lower noise, without sacrificing a very low first gear — and allows Rams to have relatively high axle ratios, for better highway economy.

So, to answer the title question — no, it probably does not, especially now that the 3.92 is available.

While the eight speed’s primary benefit for truck owners will be ease of moving from a stop with a heavy load, it also reportedly cuts a third of a second from 0-60 times, compared with the same engine connected to the six-speed automatic.

The V6 is available with the 3.21 and 3.55 ratios; the diesel, with the 3.55 and 3.92;  the Hemi six-speed with all three; and the Hemi eight-speed with the 3.21 and 3.92. (We received feedback that the 3.55 is available with the Hemi eight speed, but it does not appear in materials we’ve seen. This would not be inconsistent with past discrepancies between what is available and what is shown as being available.)

Axle ratios are different for the heavy duty pickups and the chassis cabs; these models all come with six-speed transmissions of varying capacity, including manual transmissions (diesel only).

Thanks, RamMan.

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