Adapting the

Dana Spicer Models 18 & 20 Transfer Cases


Divorced Mount Transmissions

Divorced mount transfer case adapter

Kit 320-3, divorced mounted conversion for the Dana 18 & 20 transfer cases

Kit Contents:

  • Adapter housing
  • Adapter shaft, 6 spline Dana input
  • Bearings
  • Gasket
  • Yoke, 1310
  • Fasteners
  • Instructions

This kit is preassembled for you.

Our divorced mount Dana 18 & Dana 20 conversion permits the use of a variety of different transmission applications and vehicle platforms.

The Novak divorced mount adapter is 5.75" long, as measured from the transfer case face to the center of the universal joint. The adapter itself is cast and machined high-grade aluminum alloy, featuring a strong flange and generous cross-section. The adapter shaft is machined from triple-alloy gear steel mounted in twin bearings to sustain moment loading from the forces of the transfer case helical, involute input gear.

We strongly recommend our urethane rear mount #RMU in Related Products, below. It is strong, versatile, and can be configured with your crossmember solution. See Related Products, below and remember that hard mounting is never an appropriate option and will void any adapter warranty.

Applications & Compatibility

Transmission Versions


Any transmission you deem appropriate for your project is compatible. We provide a 1310 input yoke to which you will connect a jackshaft from your transmission output.

Transfer Case Versions


All Jeep models of the Dana Spicer 18 and Dana Spicer 20 transfer cases are compatible with this adapter assembly. IH versions of these transfer cases are also compatible. The correct input bore and spline count must be observed. This adapter is not suitable for the Ford Bronco transfer case as it is of an entirely different design in attachment and drop.

Transfer Case Input Gear


Our adapter shaft is splined for six spline input gears.

  • Six-spline gears (shown, right) are most common and usually found behind Jeep T84, T90, T86, T89, T98, T18, T15 & T150.
  • The ten-spline version was only available on the 1966 - 1974 transfer cases against the Jeep T14 transmission
  • Factory Jeep TH400 to Dana 20 combinations had a fifteen-spline input gear, which must be replaced by a compatible six spline version.
  • 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.

All Warn and Saturn type overdrives are compatible with this conversion as long as the spline count is correct. We do not have replacement gears for the overdrive version.

Transfer Case Bore Size


The diameter of the transfer case center input locating bore will be either 3-5/32" or 4".

  • Most Dana 18's have a 3-5/32" bore, including those found against the T84, T90, T89 or T98.
  • Some Dana 18's have a 4" bore, including those found against the T86 & T14 transmissions (Buick V6 engines), 1966-1971.
  • All Dana 20's have a 4" bore, regardless of the transmission they were joined to.

Related Products

Urethane Rear Mount for Crossmember
Gasket and seal kit for the Dana 18 & 20 Transfer Case
Billet aluminum Dana transfer case pan
Dana 20 billet rear bearing cap
Dana 18 & 20 Input Gears

Installation Requirements

Assembly of this kit is can be straightforward. However, overall fabrication, mounting and layout considerations may make a divorced mount conversion a more advanced project.

Clocking Information & Driveshaft Clearance


The Novak adapter maintains factory clocking of your transfer case.

Transfer Case Shifter

This transmission conversion will allow for the retention of the factory Dana 18 twin-stick shifters, Dana 18 single-stick shifter, and many of the Dana 20 shifters. This aspect will depend largely on your installation.

Yoke & Driveshaft Clearance

Use of the factory size driveshaft and yoke is recommended, but there is room for larger units if desired. Our adapter design has maximized clearance between the transmission and yoke. No transmission modifications are required for clearance on this wise.


Driveshaft length changes will be required, as this geartrain combination is longer than most factory Jeep combinations. However, since the transfer case can be divorced mounted, the driveshaft angle can be shared and mitigated between the jackshaft and the rear driveshaft.


Use of factory axles is completely acceptable with this conversion. Axle upgrades are not necessary, but they may be chosen for reasons external to this transmission upgrade.

Also See