Dana Spicer Models 18 & 20 Transfer Cases
Assembly of this kit is very straightforward. However, overall fabrication, mounting and layout considerations may make a divorced mount conversion a more advanced project.
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 of a high-grade aluminum alloy, featuring a thick flange and a heavy cross-section.
The adapter shaft is mounted in twin bearings to resist moment loading from the forces of the helical, involute input gear.
The kit will come pre-assembled and ready to install to your transfer case.
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 Input Gear
The included adapter shaft is splined for either six-spline input gears, or ten-spline input gears.
Six-spline gears are predominately most common, as found with the Jeep T84, T90, T86, T89, T98, T18, T15 & T150. The rare ten-spline version is only availalble on the 1966 - 1974 transfer cases against the Jeep T14 transmission and this version of the Dana 18 will only have the 4" (or "large case") bore.
All Warn type overdrives are compatible with this conversion. Spline count information is the same.
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.
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.
Transfer Case Strength and Condition
The Dana transfer cases are uncommonly strong, compact and servicable. They are capable of power ranging up through V6s, V8s and even the Chevy Big Blocks.
It is not requisite 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. We've made our Dana 18 & 20 gaskets & seals kits and our all- inclusive master rebuild kits available for this purpose.
Transmission Rear Mount
This transfer case adapter's design is ready to accept our industry standard urethane isolator mount, available for purchase (below). This is our preferred rear mount unit. Our kit is designed for it, and its usage is essential to protect powertrain components from the flex and jar typical of any automobile, but especially Jeeps.
Whether you are assembling onto a stock cross member / skidpan or if you are setting up a high-clearance skid plate, you will find it to be a clean and simple process.
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 upgrade.