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Parts back in stock! We have just about everything available for purchase now and have ironed out our production! Stay tuned as products are updated and populated this week! (Update 6/6/22)
Parts back in stock! We have just about everything available for purchase now and have ironed out our production! Stay tuned as products are updated and populated this week! (Update 6/6/22)

4x4 Conversion Adapter for 4L80 to NP261


Often the most labor-intensive component of converting a van from 2WD to 4x4 is dealing with the transmission. 2003-2009 GM 2500/3500/4500 series vans with the 4.8, 6.0, and 6.6 engines came with the 4L80 transmission.

To convert this transmission to 4x4 with an output shaft that will match up with a transfer case used in many GM trucks, removal of the transmission and total disassembly is required. Often there can be issues with choosing the right reluctor ring and sensor, etc. 

We have an easy and extremely durable bolt-up solution that allows you to just unbolt the factory 2WD extension housing, bolt-up our billet aluminum adapter, attach a standard 4L80 4x4 extension housing (steel or aluminum), and an NP/NV 261 transfer case with the 32 spline input shaft commonly found on many models, years 1999-2006. There are no further modifications required, you've still got your original output shaft, reluctor, and sensor, and power is just now transferred to the t-case. 

We prefer to use a New Process 261 transfer case in our builds because we've found it to be the quietest and most durable. The quiet component of it is pertinent because, in a van, you're just sitting right on top of the t-case with a hole through the floor where the shifter lever comes through (see tips below for additional details)

In addition to the ease of install, the adapter also re-clocks the transfer case just slightly up to make room for our torsion bar carriage support bar, and to provide additional ground clearance in the center of the vehicle while still keeping a pretty straight shot to the front carrier yoke. 

There is a technique to mount the t-case the the 4L80 by just cutting 3" off the output shaft and the t-case input shaft, but the driveline angle is steep which may cause vibrations as well as clearance issues past the wiring harness. 

Fitment Designed for: 

Van Side - 2003-2009 Chevrolet Express 2500/3500/4500 series vans with 4L80 Transmission (4.8L, 6.0L, 6.6L). 

Note - The 4L80 transmission was used as early as 1991 and as late as 2013. We have designed this unit for the years described, but it will likely work on many applications.

Truck Side - This unit is designed to work with a standard 4L80 4x4 extension housing available here, as well as the NP261 transmission. It may work for other models, but this is how we've designed it. 

Tools Required:

Standard hand tools, threadlocker


Transmission adapter assembly, M10 hardened grade 10 studs, and grade 10 locknuts.

Construction Notes:

Machined solid billet aluminum, Grade 10 hardware

Tips / Skill Level:

1-10 (10 being most difficult) Level 2

This product may work with other model vehicles. 

Torque spec on M10 transmission case bolts and transfer case nuts is 37 Ft-lbs, use threadlocker!

Tip - When installing shift boot for your transfer case, find a heavy piece of rubber slightly larger than the hole, and cut a slit down the middle. Sandwich that between the floor of your van and your floor covering, then install your shift boot over it. This will significantly cut down on road noise and heat loss/gain. 

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. 
  • 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.