4WD Mechanix Magazine Home Page 4WD Mechanix Video Network 4WD Mechanix 'Tech and Travel' Forums Illustrated Technical Articles and How-to Site Content Directory Contact Us

Enter your keywords here and click!

Click here for  Access to the Mobile Version  of this Website!                             Click here for direct access to the 4WD Mechanix Magazine Facebook Page!  Join Us at Facebook![NKS_MENU]

Click the4WD Mechanix Video Network button for access to the HD video channel playlists. For a complete list of articles and videos, click the "Site Content Directory" button!


Advance Adapters RubiCrawler for JK Wranglers with 42RLE Transmission

RubiCrawler installation into the Jeep JK Wrangler with 42RLE automatic transmission.

     In the rocks, many Jeep owners want crawl-pace gear ratios to reduce the risk of vehicle damage and powertrain load. By crawling slowly, we can negotiate rough, rocky terrain with better vehicle control. This minimizes wheel spin while delivering exceptional torque.


     The more elaborate methods of gear reduction have involved dual-transfer case installations. Bulky, weighty and requiring chassis and driveline modifications, adding an extra transfer case is a complex approach. For some, simply installing lower ratio, low-range gearing in the transfer case has been popular—but this does not offer the same range of ratios that an extra gearbox does.


     Advance Adapters has provided an ideal solution for owners of 2003-present Jeep Wrangler and Jeep Wrangler Rubicon models equipped with the 42RLE automatic transmission. A “RubiCrawler” gearbox, essentially a two-speed planetary transmission, offers direct drive plus 2.72:1 reduction drive. The gearbox fits neatly between the transmission and transfer case, offering the driver a dramatic reduction ratio by simply moving levers.


     In addition to the Jeep’s original low-range ratio, the RubiCrawler provides an additional reduction that takes gearing down another 2.72:1! This means that the stock Jeep Rubicon low range reduction of 4:1 (NV241 Rock-Trac transfer case) can be multiplied to: 4 x 2.72 = 10.88:1!


 Yes, shifting from high range to low range plus low range of the RubiCrawler, the reduction nearly triples. With the transmission’s 1st gear ratio of 2.84:1, the Rubicon model’s 4:1 low range, the RubiCrawler’s 2.72:1 ratio and a final axle ratio of 4.10:1, the total reduction available is 127:1! Add to this the torque converter multiplication, and the torque available in the lowest gear slots is astounding!


     The RubiCrawler is well conceived. Advance Adapters RubiCrawler system, with either the twin-stick option or a universal style shifter, looks like a factory installation. Actually, the shifter components and fit-up pieces have an even more durable presence than original equipment.


     Better yet, the RubiCrawler fits the exact length and space of the stock transmission-to-transfer case adapter. This means no driveshaft cutting, mounting issues or driveline problems. Install the assembly by the instruction sheet and start enjoying an additional 2.72:1 reduction ratio!



  View the slide presentation (below), and you’ll see why I am impressed with Advance Adapters' RubiCrawler crawl box for TJ and JK Jeep Wranglers. If you need seriously low gearing for oversized tires and severe rock crawling chores, consider this alternative!



Note: The video is an .flv file, which opens automatically with Adobe Flash Player™ and other .flv supported programs. A free, secure download of Adobe Flash Player™ is available at the Adobe website. For convenience, you can click this link to access Adobe Flash Player™:


  You can view this video in either the viewer frame above or in full-screen, lower resolution format...

—Moses Ludel

Note: For current pricing and additional details, visit the RubiCrawler page at the Advance Adapters website catalog—click here for a direct link. The instruction sheets for various RubiCrawler applications are available at the Advance Adapters website or you can click links below. These installation instructions  are courtesy of Advance Adapters. They were produced by Advance Adapters for installing the RubiCrawler crawl box into Jeep TJ and JK Wrangler models equipped with the 42RLE automatic transmission. (Advance Adapters is responsible for all of the information and details described within these instruction sheets.) 

Installation Instructions:

- RubiCrawler for Jeep JK with Integrated Twin Stick Shifter

- RubiCrawler for Jeep JK Universal Style Shifter

- RubiCrawler for Jeep TJ with NP231 Transfer Case Integrated Twin Stick Shifter

- RubiCrawler for Jeep TJ with NP241 Transfer Case Integrated Twin Stick Shifter

- RubiCrawler for Jeep TJ Universal Style Shifter 

Copyright 2010 © Moses Ludel...Enjoy this comprehensive, color-illustrated article and photography by Moses Ludel. The article is available solely at the 4WD Mechanix Magazine website and can be viewed here as often as you like. If you wish to share the article with friends or professional colleagues, please refer them to 4WD Mechanix Magazine website: www.4WDmechanix.com. As copyrighted material, this article and the photography cannot be copied or distributed in any other form.—Moses Ludel