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TH400 to Dana 20 and Dana 18 Adapter Kit with 4-inch Bore in Transfer Case

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Product Details

The Novak TH400 to Jeep Model 18 & 20 transfer case adapter is compact at 2.5-inches in length. This adapter assembly is the shortest in the industry, providing a combined transmission and adapter length of 26.9-inches. The adapter itself is cast and machined of a high-grade aluminum alloy, featuring thick flanges and a heavy cross-section.

The adapter features the only twin-bearing design available in the OEM and other aftermarket versions. This prevents flex within the assembly that would allow lateral gear movement within the transfer case, which could cause case or gear breakage. Double seals ensure fluid-tight operation for many years.

These kits are for all years and versions of the popular HydraMatic 400, including Chevy, Buick and other GM, AMC Jeep, etc. and work with 2wd & 4wd versions.

Every kit comes with a new output shaft for the TH400, whether for 2wd or 4wd transmissions. 2wd versions work equally well as 4wd versions. The Novak output shaft is of an alloy steel, precision splined and hardened for a superior interchange. This shaft connects the TH400 output direct to the included adapter shaft for the strongest cobination. Installation requires disassembly of the transmission main assembly, and we recommend the services of a transmission professional. The basic installation is 3-4 hour bench job and may include simple gasket and seal replacements. Some choose this as the time for a more thorough master rebuild and update.

Dana 18 & 20 transfer case input gears are most commonly i.d. splined to 6 splines, and this is the configuration of the majority of our included adapter shafts.

International Harvester Dana 20's that had the TF-727 automatic had a 23-spline input gear, which must be replaced by a compatible six-spline version. Consult our informative Dana gears interchange chart if necessary.

It is not required that you rebuild your transfer case to successfully complete the conversion, but it may be a good time to do so if your transfer case leaks or has many miles of service.



  • Fits All with TH400 Transmission
  • 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 and instructions
  • 4-inch Bore in Transfer Case

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