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Notice! Fulfillment staff will be off site 9/30-10/6. Orders will be processed the following week of 10/9/23. Please excuse any delays.
Notice! Fulfillment staff will be off site 9/30-10/6. Orders will be processed the following week of 10/9/23. Please excuse any delays.

4L80 4x4 Extension Housing GM OE Aluminum


This is a GM performance or ACDelco OE Aluminum 4x4 extension housing compatible with 1999-2007 Silverado 2500 + 3500 vehicles & Suburban 2500s which share the same transmission body as the 2003-2009 Chevrolet Express and GMC Savana 2500 and 3500 vans.

When converting your G-series van with a 4L80 transmission to 4x4, one option is to trim the output shaft by 3" and attach an NP261 directly to this extension housing. Please note that while this method is possible, we recommend using this housing in conjunction with our billet adapter for various reasons outlined on that part page.

Both 2WD and 4x4 4L80 transmissions feature a 32-spline output with extended splines on the longer 2WD shaft, making it a common practice among custom builders to trim it down.

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 transfer case. It may work for other models, but this is how we've designed it. 

Tools Required:

Standard hand tools


Transmission adapter assembly (attaches with original vehicle M10 hardware)

Construction Notes:

Cast Aluminum

Tips / Skill Level:

1-10 (10 being most difficult) Level 1

This product may work with other model vehicles. 

Torque spec on transmission bolts is 37 Ft-lbs, recommended thread locker.

Shipping, Fulfillment, Taxes, Quality, and Returns
  • Shipping: Our components are carefully wrapped & packaged and shipped via 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 a 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 installation. Fabricated components are generally hand-built here in Colorado by seasoned professionals. Replacement or aftermarket parts are only offered in high-grade options.

    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 within 30 days of receipt. If you decide to return any components that didn't apply to your build or you changed your mind about, a shipping+15% restocking fee will be deducted from the refund.