Adapting the
GM 4L60-E (later version) Transmission
to the
Jeep & IH Models 18 & 20 Transfer Cases
Our 4L60-E (including the 4L65 & 4L70) to the Jeep New Process (or New Venture) transfer cases conversion makes for the most refined assembly both on-road and off-road, and has become a more common conversion in recent years.
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This kit is only intended for longer wheelbase Jeeps, and other specialty conversions, such as Land Rovers, Land Cruisers and other vehicles in which Jeep transfer cases would be useful.
The Adapter
The Novak 4L60-E to Jeep NP / NVG transfer cases adapter is 6.5" long for a combined transmission and adapter length of 27.5" (equivalent to a 20.5 " manual transmission).
The adapter is of billet and cast and machined of a high-grade aluminum alloy, featuring thick flanges, a heavy cross-section and strength-adding gussets.
4L60-E Versions
This kit is for use with the 4wd version (short output shaft) version of the 4L60E. However, a 2wd version tranny can be used if a 4wd style shaft is installed.
Once the 4wd shaft is installed, all versions (2wd or 4wd) and year of the HydraMatic transmission can be adapted to these transfer cases and there are no inherent advantages to the 2wd vs. 4wd transmission.
These kits are for the hexagonal, six-bolt tailhousing 4L60-E, typically made starting in 1996. Some 1997 and earlier versions have a four-bolt pattern tailhousing and non-removable bellhousing. See our Kit #107 if this describes your 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.
Transfer Case Input Gear & Overdrives Information
Our transmission mainshaft is splined for either six-spline input gears, or ten-spline input gears.
Six-spline gears (as seen, right) are predominately most common, as found with the Jeep T84, T90, T86, T89, T98, T18, T15 & T150. - The rare ten-spline version is only availalble 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 type overdrives are compatible with this conversion. Spline count information is the same.
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.
Transfer Case Strength and Condition
The Dana transfer cases are very well matched to the 700R4. They are uncommonly strong, compact and servicable. They are capable of power ranging up through V6s, V8s and even the Chevy Big Blocks.
It is not requisite that you rebuild your 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 Dana 18 & 20 gaskets & seals kits and our all- inclusive master rebuild kits available for this purpose.
Novak's optional #RM103 stainless steel mount base and urethane isolator assembly, as show attached to the adapter housing. This mount offers a strong and easy to configure crossmember mount for essentially all Jeeps. |
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Transmission Rear Mount
You may configure your rear mount using the base of the TH700R case in conjunction with the transfer case side mount. Or, you can install the Novak #RM103 foot and isolator assembly.
This mount will sit onto your stock cross member / skidpan, into which you will drill two attachment holes. Some height spacing may be required. You will find it to be a clean and simple process.
Any installation should use a urethane rear isolator. Its usage is essential to protect powertrain components from the flex and jar typical of any automobile, but especially Jeeps.
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 essentially all of Dana 20 shifters, including this twin-stick shifter kit.
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.).
Yoke to Pan Clearance
Use of the factory size driveshaft and yoke is recommended. Our adapter design has maximized clearance between the transmission pan and yoke, but it is necessary that you install your GM engine offset 1-1/4" to the driver's side.
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| The Lokar direct linkage transmission shifter offers a smart method of shift operation, especially for installers replacing a Jeep manual transmission with the automatic where use of the factory console and boot will contribute to a clean installation and a very factory look. Image courtesy of Lokar - TH350 shown. 4L60-E shifter similar. |
Driveshafts
Driveshaft length changes are nearly always required for this conversion, as this geartrain combination is typically longer than factory Jeep combinations.
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.
Vehicle Speed Sensor
The Novak adapter assembly integrates the Vehicle Speed Sensor (VSS) necessary for the operation of the 4L60-E's computer. This greatly simplifies the installation process and eliminates the need for a transfer case range switch circuit and logic, making all GM 2wd and 4wd engines, transmissions and their PCM's great candidates for the installer.
The Jeep speedometer cable or VSS can then be connected to the Jeep speedometer or gauge panel as per factory.
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 4L60E installation is typically done in conjunction with an engine conversion into the Jeep. These engines include the Chevrolet Small Block V6 (1997-2005) Gen. III+ V8 (1997- ).
In any scenario, it is critical that the engine be installed (as the Jeep engines usually are) with an offset of 1" to 1-1/2" to the driver's side. Other engine mounts on the market - especially the bolt-in versions - do not take this into account and make other placement decisions for the installer that do not take the full powertrain into account. 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 700R4 and the Dana transfer case both considered.
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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. |
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| Advanced computer modeling methods were itegral to the design of our #4L62 adapter assembly. |
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.
| While it is mechanically possible to run the overdriven 4L60E assembly against a Dana 18 that features a Warn style overdrive, consider that you'd have an overdrive ratio of 50% (25% + 25%). While this is a fascinating thing, theoretically, the velocities that it could turn within your Dana 18 could be overwhelming. You might try it for the sake of science, but don't expect to get much life out of your Dana 18 - or any other power transmission component within or behind it. |
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