Adapting the

Borg Warner T18 & T19 Transmissions

to the

Jeep Models 207, 231, 242, 249, 241J & 241OR Transfer Cases

Adapter kit for T18 to Jeep transfer cases

Kit 181-23, adapting the T18 & T19 transmission to 23 spline Jeep NP 207, 231, 241, 241OR, 242 and 249 transfer case

Kit Contents:

  • Adapter housing
  • Transmission mainshaft, 23 spline output
  • Seal
  • Gaskets
  • Fastening hardware
  • Steel mounting base foot
  • Instructions

Our T18 to the Jeep New Process (or New Venture Gear) transfer cases conversion makes for a strong and capable assembly both on-road and off-road, and it remains one of our preferred manual transmission to transfer case combinations.

The Novak T18 / T19 to Jeep New Process transfer case adapter is very compact at only 3.2" long for a combined transmission and adapter length of 15.2". The adapter itself is cast and precision-machined of aluminum alloy, featuring thick flanges, a heavy cross-section, and strength-adding gussets. The adapter itself is cast and machined of 356-T6 aluminum heat treated alloy, featuring thick flanges, a heavy cross-section, and strength-adding gussets. It is drilled for over 20 degrees of transfer case clocking locations, though the provided factory angle will suffice for most New Process transfer cases.

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 in Related Products, below.

The new Novak manufactured 23 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 spline directly into your 23 spline transfer case - a 21 spline version is not available. Details below.

Compatible NP & NVG Transfer Cases

The adapter kit is designed for compatibility with 23 spline Jeep NP207, NP231, NP242, NP249, NP241 & NP241OR "RockTrac" transfer cases. Below is a summary of spline counts and lengths usually encountered.

Transfer case seal spacer
New Process input gears come in varying spline counts and lengths. Whichever you have, we've got you covered. A seal spacer sleeve is included and pre-installed in your Novak adapter in the event your transfer case has a short input gear.
  • NP 231 - The NP231 may have 21 or 23 splines and a long or short style input gear
  • NP 242 - The Jeep version NP242 may have 21 splines for the 1987-1990 versions. When connected to the 4.0L HO engine (1991- ) the 242 will have 23 splines as will the Dodge and later V8 Grand Cherokee, AMG versions are 32 splines long
  • 249 - The NP249 always has 23 splines, but may have a long or short style input gear
  • 241OR - The RockTrac will always have a 23 spline, short style input gear. Its gear is unique and not interchangeable with any of the other versions due to the lower 4:1 ratio
  • NP207 - The NP207 may have 21 or 23 splines. Many versions feature extra-long input gears whose stick-out lengths (as measured from the front edge of the input gear to the transfer case front mounting face) longer than 2.2". These will require shortening with a cut-off saw and/or lathe and finished with edge breaking chamfers. New 23 spline NP207 input gears are available in Related Products below.

A more detailed discussion of New Process input gears is found here.

No 21 Spline Version?

The 21 spline shaft is substantially weaker than the 23 spline version. 21 spline versions were only used in the 4 cylinder applications and some very early automatic 6-cylinder versions. Novak does not make a 21 spline version of this adapter kit because of this weakness, vs. the exceptional torque created by the compound low gear of this transmission.

Our recommendation is to change the transfer case input gear to a 23 spline version. See Related Products, below.

Applications & Compatibility

Compatible Transmissions

Any Ford, Jeep, IH - 2wd or 4wd (either works equally well) versions and year of the Borg Warner can be adapted to these transfer cases.

Mainshaft replacement is largely straightforward. 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.

Some installers consider one of our complete Novak remanufactured and upgraded transmission packages. This is a professionally built and dyno-tested transmission, delivered ready to bolt into your Jeep build.

Compatible Jeeps

This kit is compatible with any Jeeps in which the Dana 300 was available, and most thereafter. This is one of our shortest 4-speed combinations and they fit nicely into the tunnel of most Jeeps.

Compatible Engines

Any engine that can be made to work with the T18 or T19 will work with this conversion. They include:

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

Chevy bellhousing T18 transmission Dana adapter
A T18 to Chevy / GM bellhousing: this combination works better than most people would think.

Related Products

Urethane Rear Mount for Crossmember
T18 Parts
T18 Shifter Stick
1976-1986 Jeep floor tunnel cover
Billet PTO Cover
NP231 transfer case parts
NP242 transfer case parts
NP242 transfer case parts
Transfer Case Input Gear, 23 Spline
Transfer Case Input Gear, 23 Spline
NP207 Input Gear 23 Spline
TurnKey T18 Transmission Package

Installation Considerations


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

Engine placement in these Jeeps should consider the following points:

  • Left-right offset location is similar to factory at ~1-1/4" to the driver's side
  • Avoid installing the engine too low (axle clearance and other issues)
  • Avoid installing the engine too high (transmission tunnel interference, etc.)
  • Set your engine to 4-7 degrees of tilt rearwards, like the factory engine & powertrain
  • It is usually best that Chevy and Gen III+ V8 engines install approximately 3" further forward, using the back of the engine block face as the datum
  • When mocking up your engine installation location, pay special attention to radiator and fan clearance.
  • Firewall modifications are not expected.

Since Jeeps featuring the T18 transmission are "high-hood", clearance for classic Small Block and high Vortec (truck style) intakes and accessories is not a problem.

GM Engine Mounts for Jeeps

Novak engine mounts are available to ease the installation of your engine.

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


Driveshaft length changes may be required. Chevy engines (with their rear distributors) can install around 3" further forward than AMC engines. It is also recommended that LS family engines be installed 3" further forward than the factory block (using the back face of the block as the datum point) for exhaust clearance, firewall access, etc.

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