Adapting the

TH700R-4 & Early 4L60-E Transmissions

to the

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

Our TH700R4 / Early 4L60-E overdrive transmission to the Jeep New Process (or New Venture Gear) transfer cases conversion makes for a strong, and versatile assembly both on-road and off-road. It is such a popular transmission swap into Jeeps, providing a reasonably compact geartrain, compatibility with excellent engines, and ease of installation.

The adapter is compact at only 1.1" long for a combined transmission and adapter length of 26.5", and is precisely machined from aluminum. Its design features a modular mounting and base, ready to accept our industry standard urethane isolator mount, available for purchase in Related Products, below.

your transmission can be either a 2wd or 4wd version, as your chosen kit comes with a new output shaft.

Option I: Conventional Non-Electronic 700R4 /4L60 Transmissions

Adapter kit for 700R4 / 4L60 to Jeep transfer cases

Kit 171-23, adapting TH700R4 transmissions to Jeep NP 207, 231, 241, 241OR, 242 and 249 transfer cases, 23 spline version

This version of our kit is for 1982-1992 700R4 /4L60 transmissions which are conventionally controlled. A new 23 spline output transmission shaft is provided, made from 300M steel and precision-machined and hardened for a long life of service. It features a governer worm gear cut into the shaft so the transmission can control its shift points.

Kit contents:

  • Adapter plate
  • Transmission output shaft, 23 spline
  • Seal
  • Gasket
  • O-ring
  • Fastening hardware
  • Steel mounting base foot
  • Instructions

Option II: Electronically 4L60E Transmissions

Adapter kit for Early 4L60E to Jeep transfer cases

Kit 171-23E, adapting the early 4L60E transmission to the Jeep NP 207, 231, 241, 241OR, 242 and 249 transfer cases, 23 spline version

Novak 131 adapter

This version of our kit is for the 1993-1996, Early 4L60-E which are electroincally controlled. A new 23 spline output transmission is provided, made from 300M steel and precision-machined and hardened for a long life of service. It comes with a reluctor ring and electronic VSS pickup to give the PCM the feedback needed for it to shift the transmission.

If you are transplanting a complete engine / transmission package then the controller is integrated with your PCM. If not, you will need to purchase a standalone control module from one of various vendors for proper operation.

Do not confuse this transmission with the 1997+ 4L60E which has a removable bellhousing and a hexagonal rear adapter bolt pattern. The conversion kit for this later 4L60E can be seen here.

Kit contents:

  • Adapter plate
  • Transmission output shaft, 23 spline
  • Seal
  • Gasket
  • O-ring
  • Fastening hardware
  • Steel mounting base foot
  • Reluctor ring, 40 tooth
  • Sensor, vehicle speed
  • Instructions

Applications & Compatibility

Compatible Transmissions

Any version and year of the TH700R-4 can be adapted using the 171 kit, including "90 degree" (Gen. I, II, III V6 & V8 Small Block or Big Block engines) and "60 degree" (early S10 Blazer 2.8L engine style) versions of the 700, as determined by your choice of engine.

Compatibility is for the 700R4 up through the early 4L60E with the four-bolt rear face.

The basic output shaft installation is a bench job best done by a skilled automatic transmission builder. It will include at least simple gasket and seal replacements, but may include fixes, updates and can even include radical upgrades.

Some customers ask us for one of our complete Novak remanufactured and upgraded transmission packages. The advantages of these professionally built and dyno-tested transmissions is worth consideration.

Compatible NP & NVG Transfer Cases

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

  • 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) is longer than 2.2". These will require shortening with a cut-off saw and/or lathe and finished with edge breaking chamfers

Compatible Engines

Any engine that can be made to work with the 700R4 will work with this adapter. Natively compatible engines such as the Small Block Chevy, Chevy V6, Big Block Chevy, and even the 1997-2006 Vortec / LS / Gen III+ engines popular choices. However, be aware of engine crank spacing issues with Gen III+ engines when used against Gen I transmissions such as the 700R4. It really is best to run the matched, later 4L60E when using a Gen III+ powerplant.

AMC engines can be adapted via a front adapter such as our 437 series kits.

Compatible Jeeps

This conversion is compatible with all longer wheelbase or stretched Jeeps. The TH350 is the only real automatic option practical for CJ5 and other short wheelbase Jeeps.

These are strong transmissions, and Full Size Jeeps such as Wagoneers, J-Trucks, etc. are conversion candidates for them. There are numerous upgrades available for the TH700R4 should stock strength come into question.

Related Products

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NP207 Input Gear 23 Spline
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NP231 transfer case parts
NP242 transfer case parts
TurnKey TH350 Transmission Package

Installation Requirements


Tools required will vary depending on which kit is selected. The automatic transmission shaft installation takes more specialized tools, knowledge, gaskets, seals, snap ring pliers, etc. We recommend the services of a professional to do this. Normal mechanics tools are required for the balance of the installation. The “E” kit requires drilling and tapping the transmission in the appropriate location per the included instructions.

Powertrain Placement

As these usually are installed as part of an engine swap setting the powertrain to the proper pitch angle is recommended - usually tilted down ~5 (3-7 acceptable) degrees. Offset will be to the right (passengers’) side because of the driver drop transfer caseand front differential (usually 1 to 1-1/2”). Consult our engine conversion guides for more specific recommendations on placement if the engine is being replaced.

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 JeepsNovak 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 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.

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.


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