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NWF BlackBox Underdrive

Black Box Logo

The Blackbox Series is NorthWest FabWorks premier line of shiftable, underdrive gearboxes. Typically mounted between the transmission and transfer case, the BlackBox is a gear reduction unit that has the ability to shift from a 2.72:1 low range back to 1:1 for existing operation.   

Original BlackBox


Released in 2005, our original Blackbox set the benchmark for advanced planetary technology. Since then, the original BlackBox has evolved into a complete product line with dozens of application combinations. The BlackBox offers a gearing solution for everyone; from the weekend warrior, to a top truck challenger.

What Advantages Does The BlackBox Low Gearing Offer?

Going from a vehicle with a stock, or single transfer case will see a massive improvement when adding the BlackBox.  Remember the control and traction you gained from that first locker, or set of new M/T tires when you first started out?  That is the type of substantial increase in capability you can expect after installing a BlackBox.

Operating a vehicle with the right gearing, and thus RPM and wheel speed for the terrain at hand is key; too low of a crawl ratio and your engine is revving high, but the reduction is too deep and you may not build enough momentum to pop up over that rock face or ledge.  Too tall, or not enough gear reduction, and the lack of control leaves you with no choice but to try to bounce off obstacles at speed.

Having an extremely low crawl ratio isn’t the key goal; the ideal 4x4 has not only low gears, but gearing OPTIONS.  Let’s dive into that next...

Having the right gear, at the right time:

There are a few ways to add gearing to your 4x4:
Lower Differential gears: 

Re-gearing your axles for larger tires can be necessity for drive-ability, however installing an axle ratio too low for your engine/tire size can leave your engine screaming on the highway to the trail, however still not offering any real substantial gear reduction.

New Transfer case gears:

You may consider a lower aftermarket gear-set for your existing transfer case.  There are quite a few kits out there to re-gear your current transfer case into a deeper low range, or install an aftermarket transfer case like the Atlas II. While generally good kits, this option leaves you with only one low range, and no gear selection.  

The final choice, the BlackBox:

Gear selection of multiple low range ratios will give your rig the control to tackle any terrain with the precise level of power required. You will have the ability to decide exactly how fast (or slow) to approach obstacles, applying torque smoothly, with less stress and shock loads placed on your drive-train. This means more trails tackled, with less repairs.

How does the BlackBox offer so many ratios?

Adding the blackbox not only offers the 2.72:1 low range, but has the ability to multiply against your existing transfer case low range offering 4 total low range options. 

Lets use a NP205 for a gear ratio example below:

BlackBox & Transfer Case in High range: 1:1, no reduction.

BlackBox in high, Transfer case in low,  ex:  1.96:1 (NP205)

BlackBox in Low, Transfer Case in High, 2.72:1  

Blackbox and Transfer case in Low 5.33:1 comound low. (2.72:1x1.96:1)

As you can see, adding the Blackbox to your drivetrain not only gives you a lower ultimate ratio, but additional ratios along the way. It is this gear selection that the Black Box provides that makes it the clear cut choice and gives the ultimate flexibility. Gear selection is #1 when it comes to building a vehicle that can conquer all types of situations and terrain. 

Competitive Advantage
At NorthWest FabWorks, we're not going to produce a product unless we're sure that we have the best available. The Black Box is no exception, holding a strong competitive advantage over all other underdrive units on the market today:  

Heavy Duty Roller Bearing Shaft Support: 
The Black Box is the original planetary gear box to have a bearing support at both the input and output of the main shaft. Our competitors rely on the input splines and bearing of your transfer case to both center and support all the output load of the gearbox. Not here. We use a massive 80mm roller bearing at the output of the Black Box.
Adjustable Shifter Assembly:
The Blackbox utilizes a versatile shifter mechanism that allows the user to infinitely adjust detent pressure for hi/lo shift. This shifter features hardened detent locks, shifter fork, and serviceable shift fork pads.
Hard Anodized Black:
All of our Black Box Gear Boxes are hard anodized black, giving a lasting consistent surface finish.
The BlackBox uses a 8620 Main shaft that has been case-hardened and hard turned for the ultimate in shaft strength and precision. Looking for a weak link? Look elsewhere.
 Billet Input Retainers:
The Black Box includes a billet input retainer with quad oiling ports. We do not re-use factory cast NVG231/241 retainers. Our retainers parts are purpose built specifically for the Black Box.

Cable Shifter:
The Blackbox comes with the option of a rugged cable shifter for easy operation from hi to low. Couple the Blackbox with one of our dual cable shifter kits and we can provide a triple shift box for an extremely clean setup.
360 Degree Clocking:
The Black Box Will allow you to rotate your transfer case 360 degrees. There is no limitations on orientation with the Black Box. No need to buy a clocking or flip ring, its built in

We've been in the underdrive business for ten years, and we manufacture the vast majority of the BlackBox parts in our manufacturing facility. Our expert employees have the experience and knowledge to guide you from application fitment to trouble shooting. You can rest assured we here for our customers.

The Evolution:


Since conception, we have continuously grown and improved on the technology.  We now have the shortest, strongest, and most diverse underdrive line available on the market today.
The BlackBox line has expanded into these diverse lines, each offering a key innovation:

BlackBox: Original, The classic that started it all.

BlackBox-i: Integrated version, as short as 4” with no drawbacks, fits Dana 300, Bronco Dana 20 and Atlas II.

BlackBox-C: Land Cruiser Edition: All the strength and technology of the original, now Landcruiser specific.

BlackBox – TITAN: The absolute ultimate in strength, NP205 specific.

Eco-Crawl: A DIY builder version.  BlackBox technology on a budget.

BlackBox Warranty Information

Products (Total Items: 8 )
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BlackBox-c Land Cruiser Edition