Advance Adapters RubiCrawler for Jeep TJ and JK Wrangler 42RLE Models

Advance Adapters RubiCrawler for Jeep TJ and JK Wrangler with 42RLE Transmission

     Note: This tour of the RubiCrawler with Steve Roberts at Advance Adapters explains the function and fit of the Rubicrawler. The ingenious gearbox occupies the factory tailhousing space on the Jeep TJ and JK Wrangler models equipped with the 42RLE automatic transmission. Without driveline modifications, this is a “bolt-in” swap with immediate and significant gearing advantages for big tires and the OE or aftermarket axle gearing.

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!

TJ Wrangler with 42RLE automatic accepts the RubiCrawler.

     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!


       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

For the complete coverage of the Advance Adapters facility, manufacturing process and product insights, see these HD 1080P videos:

     1) In this candid talk, Moses Ludel and Mike Partridge discuss 4WD industry trends and the Advance Adapters role within the 4WD aftermarket. The conversation includes new 4×4 products, popular consumer interests and keeping production in the United States. Click here for direct access to the interview! 

     2) Advance Adapters produces a variety of transfer case, transmission, overdrive and engine conversion components. The Atlas transfer case, Saturn overdrive, Rubicrawler, Ranger Torque Splitter and SYE kits are well known and produced in-house at Paso Robles, California. See the modern Advance Adapters manufacturing and machine processes that produce these components. Click here for direct access to the HD video tour! 

     3) High performance and long life products require quality engineering and testing. Advance Adapters Senior Design Engineer Chuck Althausen shares the processes, standards and unique testing that make the Atlas transfer cases, Rubicrawler, Saturn overdrive, Ranger Torque Splitter, V-8 conversions, SYE kits and other Advance Adapters products superior.  Click here for direct access to the engineering tour! 

     4) Moses Ludel and Advance Adapters Sales Manager Steve Roberts discuss details on popular engine and transmission conversions, including Atlas and Rubicrawler upgrades and meeting the challenges of emission controls. The goal is how to get maximum reliability from an upgraded 4×4.  Click here for direct access to the HD video interview with Steve Roberts! 

     5) Advance Adapters builds the Atlas transfer case, Saturn overdrive, Rubicrawler, engine conversion kits and many other specialty 4×4 parts. To design and test these components, the company has several Jeep TJ and JK Wrangler “mules”. See the Advance Adapter prototype vehicles and testing rock pile…Click here to see the Advance Adapter 4×4 fleet on the test rocks! 

     6) Advance Adapters produces the unique Rubicrawler gear reduction box for Jeep Wrangler models with the 42RLE automatic transmission. This reduction or “crawl” gear box has an easily understood shift method that Steve Roberts demonstrates in this HD video how-to. Click here for direct access to the HD video details on the Rubicrawler! 

     7) Steve Roberts at Advance Adapters shares close-up details on the Atlas transfer case. He describes the function, design and attributes of both the two- and four-speed Atlas transfer cases. Learn more about this popular and rugged upgrade for Jeep, light truck, Land Cruiser, off-road 4×4 buggy and other heavy duty applications.  Click here for insight into the Atlas transfer case design and shifting! 

     8) In this close-up video, Steve Roberts shares the Advance Adapters Jeep TJ Wrangler with a 5.3L G.M. Generation 3 V-8 swap. See how Advance Adapters makes this a 50-State emissions legal engine and transmission conversion. Click here for insight into an LS swap for a Jeep Wrangler! 

Click here for direct access to the Advance Adapters website!