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Dual Case Kit for 1995+ Chain Drive T/Case

SKU IGTC-1211Category


Availability: In stock

Availability: In stock (can be backordered)

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We are the sole supplier of Inchworm Adapters and are currently building products with them! This adapter kit allows you to mate a 1995 and newer 23-spline Chain Drive transfer case behind a Gear Drive Dual Case Reduction Unit!

Made in USA, this billet adapter allows you to bolt a 1995+ Toyota VF1A Chain Drive Transfer case (23-Spline) behind your 5-speed manual or 4-speed automatic transmission.

Top-shift style 1979-83 or 1985-88 RF1A transfer case core required to assemble into a Crawl Box.

Includes Ultra Grey silicone, Dished MC07 Coupler, Heat Treated Thrust Washer, and high quality OEM JIS Japanese hardware.

This listing is for the rear adapter. Front adapter also required & sold separately.

What does a Dual Case do?

A Dual Case has three shift positions that may be engaged from a stop:

  • High: High Range is 1.00:1 so shaft speed & torque enters and departs at the same rate and is used for normal City and Highway driving. The ECU and all associated systems such as cruise control, traction control, stability control, Toyota Safety Sense, ABS, ATRC, and Crawl Control, function normally. City and Highway Fuel Economy is unaffected. The truck will feel and operate 100% like factory both on-road and off-road, 2WD or 4WD. The Dual Case is simply bypassed.
  • Neutral: A Neutral position which many newer vehicles do not have.
  • Low: Low Range may be either a 2.28:1 or our famous 4.70:1 ratio. When engaged, your vehicle instantly has more traction, more torque, more control, with longer reaction for increased safety, as well as less bouncing, less breakage, less trail abuse, and less risk to vehicle occupants.

The end result will look like this:

Engine > Transmission > Dual Case > Transfer Case

… thus transforming your 2-speed (High/Low) factory transfer case into a 4-speed Dual Case transfer case as follows:

Factory 2-speed T/Case

High Range (1.00:1)
Low Range (2.57:1)

Marlin Crawler Dual Case 4-speed T/Case

High Range (1.00:1)
Factory Low Range (2.57:1)
Marlin Crawler Single Low (2.28:1 or 4.70:1)
Marlin Crawler Dual Low (5.86:1 or 12.08:1)

Required modifications?

Required modifications include contracting with your local driveline shop to lengthen, shorten, and rebalance your front and rear shafts, lengthen the wires of your transfer case shift solenoid (if applicable), lengthen 6mm vacuum hose to shift base and solenoid (if applicable), and install a new shift handle into your interior by cutting a 2.5″ hole in the center of your cab and modifying your center console. For automatic owners this usually involves modifying a cup holder, coin slot, or cubbyhole. For manual owners, a simple modification to your transmission boot is all that is needed. Please see our Interior Shift Handle Installation Picture Gallery for ideas!

No factory crossmember modifications are required, however, modifications to under belly skid plates may be required depending on brand. The Marlin Crawler Dual Case includes provisions for an additional transfer case mount which is optional but when incorporated is a great addition to help lengthen the lifespan of your engine mounts! If desired, we offer a Heavy Duty 6cyl wide-style OEM Toyota mount here.


Below is an example of a fully assembled Marlin Crawler Dual Case Unit
using this rear Inchworm Dual Case Adapter Kit

Weight 23.5 lbs
Dimensions 12 × 12 × 9.5 in
Make Model Year Notes
Lexus GX460 2010 - 2024
Lexus GX470 2003 - 2009
Toyota 4Runner 1996 - 2002
Toyota 4Runner 2003 - 2009
Toyota 4Runner 2010 - 2024
Toyota FJ Cruiser 2006 - 2009
Toyota FJ Cruiser 2010 - 2014
Toyota Sequoia 2000 - 2007
Toyota T100 1995 - 1998
Toyota Tacoma 1995 - 2004
Toyota Tacoma 2005 - 2015
Toyota Tacoma 2016 - 2023
Toyota Tundra 2000 - 2006

Proposition 65 Warning for California Consumers

WARNING: Products we sell can expose you to chemicals which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to p65warnings.ca.gov.

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