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Update 5/22/23 - We have updated inventory and lead times in product descriptions. We are adding instructions/sample manuals to each product and updating published parts lists support. New Ford and GM Install manuals are done!
Update 5/22/23 - We have updated inventory and lead times in product descriptions. We are adding instructions/sample manuals to each product and updating published parts lists support. New Ford and GM Install manuals are done!

6L90 Bolt-Up 4x4 Conversion Kit


Often the most labor-intensive component of converting a van from 2WD to 4x4 is dealing with the transmission. 2010-2022 GM 2500/3500/4500 series vans with the 4.8, 6.0 and 6.6 engines came with the 6L90 transmission. To convert this transmission to 4x4 with an output shaft that will match up with a transfer case used in most GM trucks, removal of the transmission and total disassembly is required to convert it to 4x4. 

We have come up with an easy and extremely durable bolt-up solution that allows you to just unbolt the factory 2WD extension housing, bolt up our steel adapter tube, pop in the Chromoly spline adapter, and a 29 spline input GM transfer case bolts right up without hassle. (The 6L90 2WD output shaft is a 36 spline shaft.)

We prefer to use a New Process 261 transfer case with a 29 spline input found in the 2001-2007 (early) Silverado and Sierra 2500/3500 series trucks. It is the quietest and most durable we've found. We have built vans with the 241 and the Magna style t-cases as well, which do interface with the same Chromoly adapter should you choose to go that route. 

At the time of writing this, we are the only company producing a durable steel version of this adapter. The Chromoly spline shaft is very hard and designed for a tight driveline fit for years of abuse, and our steel tube assemblies are sandblasted and coated with a proprietary plastic composite coating specifically engineered for under-vehicle abuse, rust resistance, and sealing from leaks over time. 

These are the most expensive components of our conversion to produce and we hope to have better pricing on them as production allows. The build process it takes to get them perfectly machined to concentric design, the coating, and the splining is very time-consuming. 

The footer on the tube assembly is designed for a standard Silverado 2500 transmission mount. 

Options available include adapters only, or you may add appropriate torsion bar carriage or standard cross-member. 

Fitment Designed for: 

Van Side - 2010-2021 Chevrolet Express 2500/3500/4500 series vans with 6L90 Transmission (4.8L, 6.0L, 6.6L). 

Footer interfaces with Anchor motor mount for Silverado trucks and works perfectly with our torsion bar carriage system. 

Tools Required:

Standard hand tools, RTV type silicone of your choice for sealant (We can prefer gaskets, but prefer to use silicone). 


Transmission adapter tube assembly, Chromoly spline shaft, tensioning spring. 

Construction Notes:

1/4", 3/16" material CNC cut A36 mild steel, schedule 40 tubing, Chromoly spline shaft, proprietary coating

Tips / Skill Level:

1-10 (10 being most difficult) Level 1

This product may work with other model vehicles. 

Torque spec on M10 transmission case bolts and transfer case nuts is 37 Ft-lbs. 

Other Pertinent Part Numbers -  Anchor 2638 Transmission mount

Shipping, Fulfillment, Taxes, Quality, and Returns
  • Shipping: Our components are carefully wrapped and packaged and ship UPS, USPS, or FedEx, depending on what is available. If you require a particular carrier, please contact us ahead of your purchase.  Customers in Colorado may arrange for in-person pickup within 1-2 business days of purchase taking noted lead times into consideration. 
  • Shipping/Fulfillment time for components: We typically ship within 1-2 business days of your order and we carefully monitor our inventory. In the event that we are unable to meet that timeframe, we will contact you and arrange either a full refund or a timeframe for fulfillment agreeable to the customer. 
  • Taxes: Colorado residents must pay sales tax of 7.5%, no sales tax is collected on out-of-state shipments currently. 
  • Quality and Returns: We are consistently complimented on the quality of our products and the ease of install. Components are hand-built here almost exclusively in Colorado by seasoned professionals who are fanatics about design and execution. If you are in any way disappointed in the components we will issue a full refund less the cost of shipping when the product is returned. If you decide to return any components that didn't apply to your build or you changed your mind about, shipping and a 15% restocking fee will be deducted from the purchase refund.