Dual Case Kit, TacoBox (MC09)

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UPDATE Nov 16, 2020: For the first time in more than a decade we are now offering the MC09 TacoBox as a Kit! The demand for this product far exceeds available inventory so we are sorry but the MC09 is not eligible with our current TURKLE Sales Event.

Other items such as the Front Adapter plate, Turbo Input Gear, and (optionally) our Competition 4.70:1 Gear Kit is on sale so it's still a fantastic time to transform your Tacoma, 4Runner, or T100 into a true Rock Crawler with the company who started it all, Marlin Crawler!

Marlin Crawler MC09 TacoBoxMarlin Crawler MC09 TacoBox, rear viewTacoBox installed into an automatic 1st gen TacomaTacoBox installed into an automatic 1st gen TacomaTacoBox installed into a 5-speed 3rd gen 4Runner
1995-2002 2.7L 4Runner (26-spline)
1995-2004 2.7L Tacoma (26-spline)
1993-1994 3.0L T100 (23-spline)
1995-1997 3.4L T100 (23-spline)
1995-2002 3.4L 4Runner (23-spline)
1995-2004 3.4L Tacoma (23-spline)
2000-2006 4.7L Tundra (23-spline)
2000-2007 4.7L Sequoia (23-spline)

What is a TacoBox

The TacoBox is a 2-speed reduction unit based on the famous 27-year time-proven Marlin Crawler Dual Case Crawl Box and is inserted between your transmission and factory chain drive transfer case. The name TacoBox derives from Tacoma + Crawl Box, and originated in the year 2000 as the first-ever Dual T/Case for a Tacoma! In order to accomplish this, two separate adapters are required as follows:

Front Transmission Adapter Kit
sold separately

The front adapter is our updated 25% stronger 5/8" thick USA-made Billet Aluminum MC30 or MC31 Adapter. This adapter converts the bolt pattern of your transmission to accept the venerable Gear Drive T/Case Reduction Housing. This required adapter is available separately (see below).

Rear Transfer Case Adapter Kit
The heart of the TacoBox!

The rear adapter is our 6th gen USA-made Billet Aluminum MC09 Adapter which bolts to the front of your stock chain drive t/case. Featuring our heavy duty double-row maximum-capacity main bearing, our dished chromoly coupler, and a 52% stronger lower idler bearing, it is simply the strongest chain drive t/case adapter available.

This is how it looks assembled:

And this is how it performs on the trail!

The heart of the TacoBox™ is the rear transfer case adapter. This 6th generation Dual Case Adapter features everything you'd expect from the quality and reliability of Marlin Crawler. First we CNC machine a block of solid Billet Aluminum and then install our Maximum-Capacity 32-ball Double Roller Bearing, the largest and strongest mainshaft bearing ever used in a Toyota Dual Case and the bearing that has powered tens of thousands of Daily Drivers, competitive Rock Crawlers, and Desert Race vehicles since 1999. Next we fit a Heavy Duty Oversized Heat Treated Coupler for the ultimate in strength and reliability. Finally, this 6th gen design carries over our Heavy Duty lower cage bearing from our Xtreme Duty adapter line, which is 84% larger with a 52% higher load rating. Unlike other lower cage bearings, our 'XD' bearing has never been reported to have overheated in very deep snow and mud wheeling. A significant amount of oil flow design has been incorporated into this adapter to ensure steady highway operation even while towing uphill in hot climates.

Our MC09 Dual Case Adapter Kit features the same exclusive advanced reliability components and designs as our world famous MC07 and MC08 Hilux Crawler kits. As such, the TacoBox is built atop more than two centuries of Dual and Triple Case research and development. We invented the world's first Dual Case Tacoma at the turn of the century and have been designing and building late-model chain drive type Dual Case setups ever since!

What is included with this MC09 Kit

  • MC09 Dual Case Adapter (pre-assembled as shown)
    • Unique bolt retention system
    • Unique shelved oiling
    • Extensive milling for increased oil capacity, cooling, & weight reduction
  • Our signature Double-row Maximum Capacity Mainshaft Bearing (pre-assembled as shown)
    • Strongest and highest load rating bearing used in any Dual Case setup
  • Our Heavy Duty 52% stronger idler cage bearing (pre-assembled as shown)
    • Imported from our Xtreme Duty adapter series
  • Chromoly Coupler (23- or 26-spline)
    • Radiused Oiling design for improved cooling
    • Longest spline length of any Dual Case coupler
  • Thrust Washer & Snap Ring
    • With proper OEM Detent System
  • Hardware Kit with proper Japanese Industry Standard (JIS) fasteners
    • All hardware required to assemble adapter onto the front of a chain-drive t/case
  • Turtle Shift Knob
  • Ultra Gray Silicone

Additional Required Parts

Front Adapter Kit

2.7L 4cyl
3.0L 6cyl
3.4L 6cyl
4.7L 8cyl
Turbo Input Gear

Product Info

Top Shift T/Case Core

1979-83 (all), or
1985-88 (4cyl EFI)
See T/Case Bible
for more info

A gear drive transfer case core will have a 2.28:1 factory Toyota low range, so from here you can build a 2.28:1 TacoBox which will transform your rig into the following:

ExampleR&PTacoBox in HI,
T/Case in 4-LOW

Normal Low Range
TacoBox in LOW,
T/Case in 2 or 4-HI
"TacoBox only"
Also, 2WD Low Range
TacoBox in LOW,
T/Case in 4-LOW

Dual T/Case Ratio!
Low Range
2.7L Manual5.2954:148:1123:1
3.4L Auto4.8835:1
* Manual equivalent when combined with an estimated 2:1 torque converter reduction

Optional Parts

23-spline Comp. 4.70:1 Gear Set

You may also build a 4.70:1 TacoBox by installing our 23-spline 4.70:1 Total-Spline Gear Set during assembly. This results in what we refer to as an Dual Ultimate Setup, or, in the case of the TacoBox, a TacoBox Supreme, which will transform your rig into the following:

ExampleR&PTacoBox in HI,
T/Case in 4-LOW

Normal Low Range
TacoBox in LOW,
T/Case in 2 or 4-HI
"TacoBox only"
Also, 2WD Low Range
TacoBox in LOW,
T/Case in 4-LOW

Dual Ultimate Ratio!
Low Range
2.7L Manual5.2954:198:1253:1
3.4L Auto4.8835:1
* Manual equivalent when combined with an estimated 2:1 torque converter reduction

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 TacoBox 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.

What does the TacoBox do

The TacoBox has three shift positions that may be engaged from a stop at any time:

  • 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, the full ensemble of 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 TacoBox is simply bypassed.

  • Neutral: Neutral is a fully neutral position and allows for such things as unloading the drivetrain to make it easier on the electronic t/case shift solenoid, if applicable. This is nice for many newer vehicles that do not have a Neutral t/case position.

  • Low: Low Range is either the default 2.28:1 core t/case ratio our famous Marlin Crawler 4.70:1 ratio (more info). When engaged, your truck instantly becomes 2.28 or 4.7-times more capable and will blow your mind at how much control the truck has and how easy it gets up and down obstacles.

The end result will look like this:

Engine > Transmission > TacoBox > Transfer Case
... thus transforming your 2-speed (High/Low) factory transfer case into a 4-speed TacoBox-equipped transfer case as follows:
Factory T/Case (2-speed)

High Range (1.00:1)
Low Range (2.57:1)
2.28:1 TacoBox T/Case (basic 4-speed)

High Range (1.00:1) ← TacoBox in High, T/Case in High
TacoBox Single Low (2.28:1) ← TacoBox in Low, T/Case in High
Factory Low Range (2.57:1) ← TacoBox in High, T/Case in Low
TacoBox Dual Low (5.86:1) ← TacoBox in Low, T/Case in Low


4.70:1 TacoBox T/Case ("Ultimate" 4-speed)

High Range (1.00:1) ← TacoBox in High, T/Case in High
Factory Low Range (2.57:1) ← TacoBox in High, T/Case in Low
TacoBox Single Low (4.70:1) ← TacoBox in Low, T/Case in High
TacoBox Dual Low (12.08:1) ← TacoBox in Low, T/Case in Low

In a 5-speed transmission example, the truck will now have 20 different forward gears and 4 reverse, making it a 24-speed truck!

Marlin Crawler TacoBox undergoing installation

Example Vehicle

If you have 33" tires, a 3.50:1 automatic 1st gear, a 4.70:1 Ultimate TacoBox Setup, and a 4.88:1 ring and pinion ratio, then your automatic truck will look like this in first gear...

High Range
Low Range
Single Low
Dual Low
Final drive ratio *   17.08:1   43.90:1   80.28:1   206.31:1
Speed at idle   4.60 MPH   1.79 MPH   0.98 MPH   0.38 MPH
Torque at idle **   171 lb-ft   439 lb-ft   803 lb-ft   2,063 lb-ft

* Static ratios listed. With an automatic, there will be additional reduction from the torque converter when not electronically locked. At low speeds, this adds for an additional 2- to 2.5-times reduction depending on ATF temperature and drivetrain load.

** Torque at idle is calculated from a conservative estimate of 10 lb-ft of torque output generated purely from the stored potential energy of rotating engine components and ignores drivetrain losses. While this is only an estimate, it shows just how drastic of a difference low gearing makes and how that with a TacoBox, no matter how loaded down you are from on-board refrigerators, roof top tent, and recovery gear, when the TacoBox is engaged the amount of required throttle to get up and over obstacles is drastically reduced due to the tremendous increase of torque.

Finally, we can now state the new advantages your truck will have with the TacoBox:

  • Increased Traction

  • Increased Torque

  • Increased Control

  • Increased Reaction Time

John Drives BigMike's Truck at 511:1
Discover how a Marlin Crawler
can make your truck unstoppable!
  • Less Bouncing

  • Less Breakage

  • Less Trail Abuse

  • Less Risk


Back in 1994 Marlin created the phrase, "Crawl Box", derived from our business name, and is the Reduction Unit used to create a Dual Case setup. Therefore, every Marlin Crawler Dual Case setup (including the TacoBox) is known as a Crawl Box.

Standard Dual Case: A standard Dual Case uses a 2.28:1 reduction that provides around an 80:1 final drive ratio. This would be a Standard TacoBox setup.

The Dual Ultimate: In our 27 years of Rock Crawling experience, we've found that the ideal ratio, a ratio that makes your truck nearly unstoppable, is around 120:1 for automatics and 220:1 for manuals. For this, Marlin created the phrase, "Dual Ultimate", where this is truly the Ultimate setup. To achieve an Ultimate, you'll need a Marlin Crawler Crawl Box with a Marlin Crawler 4.70:1 reduction. When a TacoBox is built in this configuration, it becomes an Ultimate, and as a play on TacoBell's popular burrito, is known as a TacoBox Supreme!

Additional Benefits

Incredibly safe in downhill descents and drop-offs:

A gear ratio greater than 1.00 is considered a gear reduction because the output speed is reduced by a factor equal to the ratio. For example, a 2.00:1 ratio will have an input shaft speed equal to twice that as it's output. While this is true for energy sent downstream from engine to tire, the opposite occurs in the upstream direction: That is the engine spins twice for every one revolution of the tire.

Consider what happens to the engine when a force acts against a tire. With a factory low range of about 40:1, for every tire revolution the engine must rotate 40 times. Now the gear ratio is providing resistance to motion through which is known as Engine Compression Braking. Imagine if you shut your engine off, shifted into first gear, jacked one tire off the ground, and tried turning it by hand. For you to rotate the tire manually by hand you must also overcome energy required to move each piston through its compression stroke. Using the same above example vehicle, consider this:

High Range
Low Range
Single Low
Dual Low
Engine rotations per 30° tire rotation       1.4     3.7     6.7     17.2
No. Compression Strokes, 4cyl engine     5     14     26     68
No. Compression Strokes, 6cyl engine     8     22     40     103
No. Compression Strokes, 8cyl engine     11     29     53     137
What this means is that for your tire to rotate 30° or one hand of a clock from 12:00 to 1:00, in the case of a 6cyl truck in TacoBox Dual Low, 103 engine compression strokes must be made compared to only just 22 for the factory low range. Compared to the factory low range, the TacoBox creates 4.7-times more Engine Compression resistance to movement providing 4.7-times more control, reaction time, and safety while also 4.7-times less required brake force when going down even the steepest drop-offs and ledges.

Think of it this way: Your truck can weigh nearly 5 times more than factory and yet will still descend down hills equally as safe as a factory truck, traction limited of course. Going downhill is EXTREMELY safe with a TacoBox which provides UNPARALLELED driver control with no brakes required!

2WD Low Range:

The TacoBox also provides a new Low Range that can be used independently of your factory transfer case, meaning you can now have Low Range even while in 2WD! This is very useful if you are backing a boat down a ramp, moving a trailer around your yard, or repositioning your truck in a tight camp ground and don't want to hassle engaging 4WD. Also, on the trail you can make sharp corners without having the issue of the front end binding with the rear end due to sharp corner radii. The new ways you may manipulate your truck is very useful with cutting brakes and performing other slow and controlled maneuvers on the trail.

Extra Drive train Mount (optional):

As mentioned, the TacoBox includes provisions for a 1979-1995 style Toyota 4cyl or 6cyl crossmember mount which may be used for additional drive train support! This is entirely optional but is a great feature that spreads the drivetrain torque helping prolong the lifespan of your engine mounts. For this, we offer a Heavy Duty 6cyl wide-style OEM Toyota mount here. Depending on application, exhaust modifications may be required. Click to view an example image of a HD OEM 6cyl mount installed.

Full List of Benefits:

In conclusion, here is a comprehensive list of benefits for both Automatic and Manual Transmission owners that you get from the Marlin Crawler TacoBox. Click the image for a larger view, and consider scrolling down to watch our many YouTube action videos below!

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 www.p65warnings.ca.gov.

Marlin Crawler Dual Case Explained

Watch as BigMike explains how our Dual Transfer Case System works
at the 2017 FJ Summit in Ouray, Colorado (conversation begins at the 50-second mark)

How our TacoBox improves your truck's off-road capability

Short TacoBox Demonstration at Outer Limits

Automatic TacoBox Demonstration in 3rd Gear (91:1)

Rock Crawling Throttle Finesse with an Automatic

Using a Starter to verify Dual Case Load Reduction

Walking The Crawler up "The Wall" @ 580:1

Climbing "The Wall" at Poughkeepsie Gulch
with No Throttle in a 2016 Toyota Tacoma

Downhill with NO driver in a 2016 Toyota Tacoma

Dual Case Engine Compression Braking Demonstration

580:1 Triple Case TacoBox Demonstration