Adapting the
Turbo Hydramatic 700R-4 & Early 4L60E Transmissions
to the
Jeep Models 207, 231, 242, 249, 241J & 241OR Transfer Cases
Our TH700R4 / Early 4L60-E overdrive transmission to the Jeep New Process (or New Venture) transfer cases conversion makes for a very strong, and capable assembly both on-road and off-road. It is one of the most persistently popular transmission swaps into Jeeps, providing a very compact geartrain, compatiability with excellent engines and ease of installation.
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Option I: 700R4 / 4L60, conventional The adapter kit is designed for compatibility with the Jeep NP207, NP231, NP242, NP249 & NP241OR "RockTrac" transfer cases.
The Adapter
The Novak 700R to Jeep New Process transfer cases adapter is very compact at only 1.1" long for a combined transmission and adapter length of 24.6" (equivalent to a 18.1" manual transmission). Especially important for short wheelbase YJ & TJ Wrangler Jeeps, the Novak kit provides an excellent and popular transmission conversion combination.
The adapter itself is machined of a high-grade aluminum alloy, featuring thick flanges and a heavy cross-section.
700R-4 Versions
These kits are for the square, four-bolt tailhousing 700R-4 / 4L60 or 4L60-E, typically made through 1995. Some 1996 and later versions have a hex, six-bolt pattern tailhousing and removable bellhousing. See our Kit #4L61 if this describes your transmission.
We offer two adapter kits:
- Option I is for the 700R4 (aka, 4L60), which is the conventional, hydraulically controlled transmission. See kit #171, shown above.
- Option II is for the 4L60-E, which is the electronically controlled version of the 4L60. See kit #171-E, shown above. This version permits you to use the electronically controlled 4L60-E (four-bolt version) with your NP / NVG transfer case. Note that you will need to mildly modify the 4L60-E tailhousing (instructions included) to install the included vehicle speed sensor (VSS). Also, make sure to plan on connecting your transmission to the GM ECM (if doing a GM engine swap) or get a standalone electronic transmission controller, available from GM, TCI, Jet, B&M and others.
Any version and year of the TH700R-4 can be adapted to the NP transfer cases, 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.
Transmission Output Shaft Replacement
This #171 kit comes with a new output shaft to be installed in your 700R transmission that was originally a 2wd or 4wd version - either works equally well. The Novak output shaft is of a premium alloy steel, precision splined and specially hardened for strength and against wear, providing a superior interchange. This shaft connects the transmission output directly into the existing 21 or 23 spline NP / NVG input gear for the strongest connection. Transfer case disassembly is not typically required. However, please note our 21 vs. 23 spline discussion below and its warranty caveat.
Installation requires disassembly of the transmission for which we recommend the services of a transmission professional, though good work is within reach of the home mechanic. The basic installation is 3-4 hour bench job and may include simple gasket and seal replacements. Some choose this as the time for a more thorough master rebuild and update if necessary.
Transfer Case Input Gears
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New Process input gears come in varying spline counts and lengths. Whichever you have, we've got you covered. |
 21 vs. 23 splinesWe're often asked about whether the 21 spline style connection is strong enough, vis a vis the 23 spline version. In most situtations, 21 splines will be adequate.  This is due to the fact that we don't use friction welding on our shafts, and that much of the punishing torque multiplication takes place within the transfer case low range, which occurs after the input portion of the transfer case. However, we have seen limited instances where 21 spline shafts have failed where 23 would not have. As such, our parts warranty extends only to our 23 spline version shaft. If you are certain that you must have maximum strength, then you may purchase from us a 23 spline input gear for your NP2xx in conjunction with the 23 spline version of our kit. However, this may not be money best spent in some situations. |
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231 Rebuild Components
It is not requisite that you rebuild your Jeep 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 NP 231 rebuild components available for this purpose.
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Transmission Rear Mount
This transfer case adapter's design is based on Novak's Universal Series adapters that feature a modular mounting and support system. Included with the adapter kit is a steel base that is a highly configurable mounting foot, and is ready to accept our industry standard urethane isolator mount, available for purchase (below). This is our preferred rear mount unit. Our #171 kits are 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.
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| The Novak #SK2X shifter assembly as attached to our #171 adapter kit with a GM automatic. |
Transfer Case Shifter
This transmission conversion will allow for the retention of the factory shifters, or allow you to upgrade to the Novak #SK2X shifter assembly for a simpler conversion and a clean shifting, direct linkage system.
Transmission Shifter
A broad variety of transmission shifters are compatible with this conversion, ranging from console shifters (i.e.; Art Carr, B&M, etc.), to direct-mount stick shifters (i.e.; Gennie, Lokar, etc.).
Driveshafts
Driveshaft length changes are often required, as this geartrain combination is typically longer than factory Jeep combinations. However, some GM engine installations will allow for the transfer case to remain in its OEM location.
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| A 231 transfer case with the Ultra SYE kit installed in a TJ Wrangler. |
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, sometimes to the detriment of the project. Driveshaft modifications are usually inexpensive when performed by driveline, RV or tractor implement specialists. New driveshafts are an option but seldom a requirement in regards to the actual successful conversion. Jeeps that require extensive travel or specialty-built driveshafts have this option available through several fabricators across the nation.
Since driveshaft modifications may be indicated for the conversion, it may be a good time to convert the transfer case to a heavy duty mainshaft and ultra-short tailhousing assembly. The #231XS Slip-Yoke Eliminator is the ideal solution to capture 7" of driveshaft length, significantly reducing u-joint strain and vibration.
Transmission Cooling
For every 10 degrees cooler you can keep the transmission, you can add 25,000 miles to its service life. Therefore, use of a transmission oil cooler is advisable for this automatic transmission.
Use of a transmission temperature gauge is also a good idea. These are widely available and generally inexpensive.
With the increase in popularity of the newer, hotter burning, fuel-injected engines, it is increasingly wiser to run a stand-alone, dedicated transmission fluid cooler.
Engines & Engine Mounting
A Turbo 700R-4 installation is typically done in conjunction with an engine conversion into the Jeep. These engines include the Chevrolet Small Block V6 & V8, from Generations I, II, & III, 1955-2006.
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| Novak's MM Series 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. |
Novak offers what we have found to be the most intelligent engine mounting system for Jeeps available, allowing the installer to make an easy and satisfying decision as to powertrain placement with the TH700 and the Jeep transfer case both considered.
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.
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| We’ve seen three shafts broken like this one, and heard our customers speak of more failures of output shafts made by other adapter companies. This is why we go through the trouble and expense of making our output shafts from a solid bar of alloy steel, instead of friction welding salvage GM shafts. A second, sometimes less obvious but pernicious problem is the issue of warpage during friction welding and heat treating - which cannot be corrected when the shaft journals are already ground and worn at or below factory specifications. The Novak shaft in our #171 kit is produced faithfully to factory specifications, and using even better steel. Our 4-axis CNC cut of the spiral gear and other features are no small tasks, and likewise, no small benefit to our customers dedicated to putting their Jeeps together right. |
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| Advanced computer modeling methods were itegral to the design of our #171 adapter assembly. We were able to push the bounds of product and process well beyond the status quo. |