Adapting the
Turbo Hydramatic 700R-4 & 4L60-E (early version) Transmissions
to the
Jeep Dana Models 18 & 20 Transfer Cases
Our TH700R-4 to Dana Models 18 & 20 conversion makes for a very strong, and capable assembly both on-road and off-road, and it remains one of our most requested automatic transmission conversions.
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.
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Option I: 700R4 / 4L60, conventional The Adapter
The Novak TH700R-4 / 4L60 to Jeep Dana 18 / 20 transfer case adapter is:
Dana 20 version: 4.5" long for a combined transmission and adapter length of 27.9".
Dana 18 version: 5.25" long for a combined transmission and adapter length of 28.6".
The adapter itself is cast and machined of a high-grade aluminum alloy, featuring thick flanges, a heavy cross-section and strength adding gussets.
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 #4L62 if this describes your transmission.
We offer these adapter kits:
- Option I is for the 700R4 (aka, 4L60), which is the conventional, hydraulically controlled transmission.
- Option II is for the Early 4L60-E, which is the electronically controlled version of the 4L60. This version comes with a pre-installed 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 Jeep 18 or 20 transfer case, 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
4wd versions of the Turbo 700R-4 / 4L60 and early 4L60-E are nearly ready to bolt up to our adapter assembly as the required style of output shaft is already installed.
2wd versions work equally well, but you will need to install a 4wd style transmission output shaft (order, below). This particular 4wd shaft will protrude about 3" from the rear face of the case. We carry good, used GM shafts for this purpose.
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| The 4wd version of the 700R-4 will have ~3" of stickout from the rear face of the transmission. |
This requires disassembly of the transmission, and we recommend the services of a transmission professional. 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.
Dana 20 version: The installation of this adapter kit requires that the GM output shaft be cut shorter by 5/8 ". This should be done with a cut-off wheel and with care to prevent any debris from getting into your transmission, as discussed in the enclosed instructions. This step is required so that we can keep this adapter assembly as compact as possible.
Dana 18 version: No shortening of the transmission output shaft is required.
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. |
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 the Twin-Stix 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. If you are installing against a factory AMC engine with our #437-AMC adapter kit, your factory engine should already have this proper offset.
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.
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| Our RadLock radiators offer an available integrated transmission cooler, to greatly add to the life of your HydraMatic transmission. |
Transmission Cooling
For every ten 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.
We will suggest the use of our RadLock high-performance conversion radiators, which can include an integrated transmission fluid cooler. You may also use a standalone / supplemental transmission cooler depending on your driving style and climate conditions.
Engines & Engine Mounting
A 700R4 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. Carbureted, TBI and TPI engines prior to 1993 will usually be paired with the classic, hydraulically shifted version of the 700R4.
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| Novak's MMX Series engine mounts, featuring excellent vibration dampening, superior strength and impressive adjustability - adjustable even after the engine is installed. The design and strength and affordability of our mounts are second to none. |
The electronic version of this transmission, the 4L60-E, will usually be done with a 1993-1997 powerplant and ideally sourced from the same GM vehicle for the sake of simplicity in wiring and computer programming, if any.
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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| Advanced computer modeling methods were itegral to the design of our #107 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 700R 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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