Adapting the

New Process 435 Transmission

to the

Dana Spicer Models 18 & 20 Transfer Cases

Adapter kit for NP435 to Jeep Dana transfer cases

Kit 432, adapting Ford or Dodge NP435 transmissions to the small bore Jeep & IH Dana Spicer Model 18 & 20 transfer cases

Our NP435 to Dana 18 & Dana 20 conversion creates a robust geartrain assembly for broad use in severe terrain or tame roads. It is one of more popular manual shift transmission conversions into Jeeps, providing a compact geartrain, an extremely low crawling gear, compatibility with several engines, and straightforward installation.

np435_2wd_gasket np435_4wd_gasket

The Novak NP435 to Jeep transfer cases adapter is 3.5" long for a combined transmission and adapter length of 14.2". The adapter itself is cast and machined of 356-T6 aluminum alloy, featuring thick flanges, a heavy cross-section, and strength-adding gussets.

Kit Contents

  • Adapter housing
  • Transmission main shaft, 6 or 10 spline
  • Fasteners
  • Seal
  • Gaskets
  • Instructions

Applications & Compatibility

Compatible Transmissions

NP435 transmission with Novak adapter

All Ford versions and most Dodge versions of the NP435 can be adapted to these transfer cases. GM NP435's and Dodge NP435's (early) are not compatible due to their input shaft ball bearing and snap ring mainshaft design. There are no inherent advantages to the 2wd vs. 4wd transmission. Note that divorced 4wd applications of the NP435 often (but not always) used a 2wd style tail housing and yoke. More details concerning this are discussed here.

Mainshaft replacement is feasible by the home mechanic. Good work is within easy reach of the careful home mechanic and instructions are included. We also recommend our basic gasket & seal kit, or this is a good time for a more thorough master rebuild and update of the transmission.

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

dana_18_20_input_gearOur 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.

Compatible Jeeps


This kit is compatible with most Jeeps that originally featured the D300 transfer case. If you are retrofitting both, keep in mind length and shifter location to ensure clearance for both. With a properly set-up short tail D300, this is as short as it gets for a 4 speed into a Jeep.

Compatible Engines

Any engine that can be made to work with the NP435 will work with this conversion. They include:

Ford and AMC engines are the two most natural and recommended choices for this transmission.

Rear Mount Provision

This transfer case adapter's design features a modular mounting and support system and mounting base, ready to accept our industry standard urethane isolator mount, available for purchase below.

The new Novak manufactured 6 or 10 spline output shaft is machined from premium alloy steel and hardened for maximum strength and longevity ready to be installed in your Borg-Warner transmission and then the D18 or D20 input gear attaches directly to it.

Related Products

Urethane Rear Mount for Crossmember
Shifter Retention Kit, SM420, SM465, T176, NP435
Dana 18 & 20 Rebuild Kit
Billet aluminum Dana transfer case pan
1976-1986 Jeep floor tunnel cover
Dana 20 billet rear bearing cap
Dana 18 Billet PTO Cover
Billet PTO Cover
Ford Engine Mounts for Jeeps

Installation Requirements


The transmission shaft installation takes more specialized tools, heavy snap ring pliers, a press to remove and replace bearings, etc. Normal mechanics tools are required for the balance of the installation.

Engines & Engine Mounting

GM Engine Mounts for Jeeps

Factory engine placement on CJ Jeeps is good for the NP435 transmission, whether using an AMC I6 or V8 engine. If installing an AMC or other V8, your engine mounts should permit about a 1-1/4" offset towards the driver's side. Novak's engine mounts, feature vibration dampening, superior strength.

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. Some tube-mounted Dana 20 shifters may need to be modified, or replaced with a twin-stick shifter kit. Dana 18 shifter clearance on some versions may require some grinding of an SM465 gusset for clearance.


Driveshaft length changes are often required. Most conversions to these transmissions will require that the rear driveshaft be modified to be shorter and front driveshaft longer.

Some installers, concerned about the expense of new or modified driveshafts, attempt to let the existing driveshafts dictate engine, transmission and transfer case location, often to the detriment of the project. Our recommendation is to prioritize the correct position of drivetrain components over saving a few dollars which is usually regretted in the long run with compromised positioning.

Jeeps that require extensive travel or specialty-built driveshafts have this option available through several fabricators across the nation. These are normally specified after placement of the new transmission and measured at vehicle ride height. As the rear driveline gets shorter, it is often advantageous to us a Double Cardan or “CV style” rear shaft with the correct geometry at the axle to minimize vibrations and possible binding.


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