Novak TH400 to Jeep Model 18 & 20 Transfer Case Adapter

Upgrade your Jeep's drivetrain with the Novak TH400 to Model 18 & 20 Transfer Case Adapter, designed for maximum durability and precision. This compact adapter measures just 2.5 inches in length, providing a shortest-in-class combined transmission and adapter length of 26.9 inches. Built with high-grade aluminum alloy, the adapter features thick flanges and a heavy cross-section for superior strength and performance.

The twin-bearing design of this adapter is unique, offering the most robust and flexible solution in the industry. It prevents flex within the assembly, ensuring gear stability and minimizing the risk of lateral gear movement that could otherwise lead to gear or case failure. Double seals ensure a leak-free and reliable performance over the years.

Designed to work with all TH400 transmissions, including those from Chevy, Buick, GM, AMC, and other models, this adapter is compatible with both 2wd and 4wd versions. The kit includes a new output shaft made from alloy steel, precision splined, and hardened for superior strength. Whether you have a 2wd or 4wd transmission, this output shaft connects directly to the adapter shaft for the most secure and powerful setup.

Installation typically requires disassembly of the transmission, and while a professional transmission technician is recommended, the basic installation can be done in about 3-4 hours with some simple gasket and seal replacements. Many enthusiasts use this opportunity to perform a full rebuild and update of their transmission system.

Note: Most Dana 18 & 20 transfer case input gears are 6-splined, which aligns with the adapter shaft configuration. However, if you’re using an International Harvester Dana 20 with a TF-727, you’ll need to replace the input gear with a compatible 6-spline version. Check our Dana gears interchange chart for guidance.

This adapter does not require a transfer case rebuild to complete the conversion, but if your transfer case is worn out or leaking, now may be the perfect time to give it a refresh.

Kit Includes:

• Adapter casting
• Bearing retainer
• Output shaft
• Adapter shaft
• Deep ball roller bearings
• Snap ring
• Oil seals
• Gasket
• O-ring
• Input gear nut & washer
• Fastening hardware
• Detailed instructions

Fits all TH400 transmissions and is designed for Jeep Model 18 & 20 transfer cases with a 4-inch bore.

Upgrade your drivetrain today with the Novak TH400 to Model 18 & 20 Transfer Case Adapter, engineered for strength, precision, and long-lasting reliability!