Adapting the

New Process & Dana 300 Flanged Transmissions

to the

Jeep & IH Models 18 & 20 Transfer Cases

Adaptation of newer Jeep four- and five-speed transmissions into earlier Jeeps is now feasible. This kit is only intended for Jeeps that have the length necessary to accommodate these longer transmissions.

Product & Features

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The Adapter

The Novak #152 adapter is 2" long. While this is very compact for a twin-bearing adapter, the mating transmissions may prove long for some early Jeeps. For your reference, some combined lengths include: 

  • AX15, 16-1/2" (+ 7-1/2" bellhousing*)
  • NV3550, 16-1/2" (+ 7-1/2" bellhousing*)
  • NSG370, 24" (integrated bellhousing*)
  • T176, 16-1/2" (+6-3/4" bellhousing*)
  • T5, 17-1/2" (+6-3/4" bellhousing*)
  • TF999, 24-3/4"
  • AW4, 27-3/8"
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Advanced computer modeling methods were integral to the design of our #152 adapter assembly.

Most of these lengths will not be appropriate for early CJs (pre-1972) with short wheelbases, unless the engine is a V6 and has been installed in as far forward a manner as possible.

The adapter is machined from corrosion resistant 6061 aluminum. The included adapter shaft is available as a 23 spline input and 6 spline output only.

*AMC / Jeep bellhousings. May vary slightly when adapted to GM or other bellhousings.

Transfer Case Clocking & Rotation Options 

Our adapter is drilled for multiple clocking locations from near-factory (20 degrees down) to near-flat (3 degrees down). However, pan clearances and front axle width may inhibit the flatter options.

Contents

The 152 kit includes adapter housing, adapter shaft, bearings, seals, correct locator for your transfer case model bore, hardware, and instructions. These parts will come assembled to the extent possible.

Applications & Compatibility

Transmissions

While it is mechanically possible to run the overdriven 700R4/4L60E assembly against a Dana 18 that features a Warn style overdrive, consider that you would have an overall overdrive ratio of .525 (.70 in the transmission and .75 at the transfer case overdrive). Transfer case output speed would be nearly double that of the engine speed. While this is a fascinating thing and excellent for mileage if the engine can sustain the low RPM cruise, the velocities that it could turn within your Dana 18 may be overwhelming. Keep in mind that the D18 and its overdrive were not designed for that type of RPM use. You would likely run into oiling and sheer strength issues at those sustained speeds.

The following transmissions are possibilities for such a conversion:

  • AX15
  • NV3550
  • T176
  • T5
  • TF999
  • AW4
  • TF904

Jeeps 

Again, most of these lengths will not be appropriate for an early CJ (pre-1972) with short wheelbases, unless the engine is a V6 and has been installed as far forward as possible.

However, CJ8 Scrambler Jeeps, other longer Jeeps (especially the full sized trucks and Wagoneers) are ideal candidates if punishing transmission duty is a prime consideration.

Engines

Engines are dependent on the transmission selected for use with this kit. Keep in mind length on shorter model Jeeps.

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 and must be replaced with a 6 compatible spline version.
  • 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.

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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

Dana 18 & 20 6 Spline Input Gears

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Transmission Tunnel Cover

Because the transmission and transfer case shifters are often in a different location than factory in these Jeeps, this new transmission tunnel cover gives the installer a clean slate. There are no screw holes nor transmission & transfer case shifter holes, allowing the installer to drill and cut them as necessary. An easy way to get a perfect fit is to use the old cover as a template, making cuts as necessary, then overlay on the new aluminum piece for perfect holes.

The finish is natural brushed aluminum, which looks pretty terrific, but it can easily be primed and painted to suit, if desired.

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D20 Transfer Case Shifters

The stock transfer case shifter may be used, possibly requiring minor modifications. On the Dana 20 it is often advantageous to use a new twin stick style shifter, especially if you are able to remove the interlock pins during the transfer case rebuild process. Multiple models are available depending on your original transmission mated to the D20. It is also possible to retrofit a longer length shifter by using our replacement tubing and TX20-COM4 sold below. You will likely need to re-bend the shifter levers for correct positioning but this gives a sound starting point. Going this route allows the shifter to be positioned further forward in relation to the transfer case which allows a location closer to stock as the transfer case moves back with the longer length TH350.

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This is the tubing necessary to fabricate a custom length shifter, sold by the inch.


All would require the

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D18 & D20 Rebuild and Gasket Options

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Gasket and seals kit

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Dana 20 Billet Pan and PTO Cover

These rigid and precisely machined billet bottom pans are the answer to a few Dana transfer case dilemmas. The thick, smooth-finished flange replaces the thin, warped factory pans and they virtually assure a drip-free seal. The PTO cover does the same for the back, plus they add a little “bling” to your case.

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Dana 18 & 20 3.15:1 Upgrade Gearset

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Installation Requirements

Tools

The adapter requires typical mechanic's hand tools. Detailed instructions are included for installation of the adapter to transfer case.

Placement

Transmission placement is largely determined by factory engine location. It is not necessary in typical conversions to change the engine position unless an engine is being swapped in at the same time, as will often be the case with these kits. Setting the powertrain to the proper factory or conversion pitch angle - usually tilted down ~5 (3-7 acceptable) degrees - is recommended. Consult our engine conversion guides for more specific recommendations on placement if the engine is being replaced.

Clocking Information & Driveshaft / Yoke to Pan Clearance

Our adapter is drilled for multiple clocking locations check clearance carefully as you complete the installation.

Engines & Engine Mounting

mmtj-g3If converting to a V8 in conjunction with this upgrade, aftermarket engine mounts are available to ease its installation. Because of the broad spectrum of engines and vehicle combinations used with this adapter, it would be difficult to list them all here. Whatever your application, Novak likely has the perfect solution. From a 225 Buick V6 in a CJ2A to an LS3 in your JK, we’ve got you covered. 

Novak's engine mounts, featuring excellent vibration dampening, superior strength, and impressive adjustability - adjustable even after the engine is installed. The design, strength, and affordability of our mounts are second to none.

Engine Placement

Engine placement in these applications is an effort in compromise to find the best position overall as a package. Generally the engine will be about 1” or even more towards the left, (driver’s side in the USA) away from the front differential in a CJ application. This gives the best balance of weight and more importantly clearance for the driveshaft going to the front axle. Your tight spots will be steering to exhaust on the left (hold that as tight as you can) and clearance for the front driveshaft on the right. Fore and aft position will vary with the Jeep model and engine. Have a CJ5 and Gen I with a rear distributor? You’ll be better off a little forward for more rear driveshaft length and clearance for that HEI. If you are in a longer Jeep and using an LS engine with no distributor, you’ll have more fan clearance and better balance if you hold it to the rear. Usually for ground clearance tuck things up nicely for height to avoid damage to oil pans and other life giving parts in the Jeep. Common sense and taking a step back to look at things overall goes a long way.

Driveshafts

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 of our customers, fearful at the perceived expense of new or modified driveshafts, attempt to let the existing driveshafts dictate engine, transmission and transfer case location, usually to the detriment of the project. Our recommendation is to always value the correct position of drivetrain components over saving a few dollars which is usually regretted in the long run with compromised positioning. Sometimes the application allows use of the existing shafts without modification. While that is perfectly acceptable, it should not be the first priority. Driveshaft modifications and rebalancing can be affordable when performed by driveline, RV or tractor implement specialists. New driveshafts are an option, but not necessarily a requirement in regards to the actual successful conversion if your existing driveshafts are in good condition. 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. Novak can also accommodate your needs on this if provided with dimensions for the shafts at a reasonable rate.

Axles

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