The Jeep Wrangler is one of two vehicles still being built with
Mercedes' five-speed automatic (made by Chrysler in Indiana). The reason
for that, according to Allpar sources, is the length of the ZF
eight-speed which would be much better for Wrangler: it may fit into the
Unlimited, but it won't fit into the standard Wrangler.
Even
when the next-generation "JL" Wrangler arrives, that transmission will
be too long, as it's made now. Yet, Automotive News and Allpar have both
heard that the iconic Jeep will indeed have the eight-speed, which is
practically mandatory if one wants to get the most out of the Pentastar
V6 engine - especially if the Wrangler drops down to the 3.2 liter
version, as we expect.
The solution may be to carefully alter the
transmission and transfer case, according to former Jeep engineer, and
current engineer-at-large, Robert Sheaves. See his illustrated article
to learn more about how the eight-speed can be shoe-horned into even
short-wheelbase Wranglers.
As read on: http://www.allpar.com/news/index.php/2014/12/fitting-8-speeds-into-wrangler