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Adapting the

GM 4L60-E (later version) Transmission

to the

Jeep & IH Models 18 & 20 Transfer Cases

Our 4L60E (later version) to Dana Models 18 & 20 conversion makes for a very strong and capable assembly both on-road and off-road. Because of the assembled length, 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.

Product & Features

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About the Adapter

The Novak 4L60-E to Jeep NP / NVG transfer cases adapter is 5.5" long for a combined transmission and adapter length of 26.5" (equivalent to a 19.5" manual transmission).

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Advanced computer modeling methods were integral to the design of our #4L62 adapter assembly.

The adapter is comprised of two main components. The transmission half is machined of a 6061T6 billet aluminum alloy, featuring thick flanges and a heavy cross-section. The transfer case half is comprised of cast and machined high-grade aluminum alloy, featuring thick flanges, a heavy cross-section, and strength-adding gussets. The adapter shaft is machined from triple-alloy gear steel and provides superior strength as it is carried by two bearings unlike the other single bearing versions on the market. The Dana 18/20 input is completely supported by this shaft and, due to the helical cut, is subject to side loading. The two bearing design is much better equipped to handle these loads.

Contents

The 4L62 Kit includes adapter housings, adapter shaft, bearings, seals, correct locator for your transfer case model bore, sensor with reluctor, hardware, and instructions. These parts will come assembled to the extent possible. 

 

Applications & Compatibility

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The 4wd version of the 700R-4 will have ~3" of stick out from the rear face of the transmission.

Transmission Versions

All versions and years of the TH700R4 and 4L60E can be adapted to the Dana 18 & 20. The classic Chevrolet V8, 90 degree V6 pattern, the less common 60 degree pattern used with the 2.8L in earlier Camaros and S-10 model trucks, and 3.8L Buick in some later 90’s era Camaros will all accept the adapter. Either transmission version requires a 4x4 version output shaft be installed if it is not already there and cut to proper length. Those are available below and correct cut procedure with lengths needed are addressed in the instructions and noted below. The basic installation is a 1.5-2 hour bench job and will include at least simple gasket and seal replacements. This is a good time for a more thorough master rebuild and update of the transmission. Many consider one of our complete Novak remanufactured and upgraded transmission packages. The advantage of a superior, professionally built transmission, tested and ready to bolt in delivered to you is definitely worthy of consideration.

4L60-E Versions

This kit is for use with the 4wd version (short output shaft) version of the 4L60E. However, a 2wd version transmission can be used if a 4wd style shaft is installed. Once the 4wd shaft is installed, 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 1999 and earlier versions have a four-bolt pattern tailhousing and non-removable bellhousing. See our Kit #107 if this describes your transmission.

The 4L60E is an electronically controlled transmission and requires a computer to control it. If you are transplanting a complete engine/transmission package then the controller is likely there. If not, you will need to purchase a control module for proper operation. We have two versions available below if you need one of those.

Jeeps

While it is mechanically possible to run the overdriven 700R4/4L60E assembly against a Dana 18 that features a Warn style overdrive, consider that you would have an overall overdrive ratio of .525 (.70 in the transmission and .75 at the transfer case overdrive). Transfer case output speed would be nearly double that of the engine speed. While this is a fascinating thing and excellent for mileage if the engine can sustain the low RPM cruise, the velocities that it could turn within your Dana 18 may be overwhelming. Keep in mind that the D18 and its overdrive were not designed for that type of RPM use. You would likely run into oiling and sheer strength issues at those sustained speeds.

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. 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 Transmission should stock strength come into question. 

The TH350 is the only real automatic option practical for CJ5 and other short wheelbase Jeeps. Our 103 kits are best for these versions. 

Engines

Any engine that can be made to work with the 4L60E will work with this adapter. All of the above mentioned native engines along with others that can be adapted via a front adapter such as our 437 series kits open up numerous possibilities.

There were also a lot of other combinations available to the 4L60E that may not be perfect candidates for a Jeep swap. The Atlas series inline engines, 3.8L in the 90’s era Camaro, a rear configuration for the Corvette, and there is even a Bellhousing available in Australia for the Holden that will allow a High Feature DOHC V6 to mate to the 4L60E. Sometimes just because it’s possible doesn’t make it a good idea, but we’ll leave that part up to you.

Keep in mind that if you stray from a native configuration on the engine, you will need an aftermarket controller for the transmission as these are electronically controlled both in the shifting and pressure. Without a controller you’ll have reverse, third and max line pressure, which is probably not the best solution for a Jeep.

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. The correct input bore and spline count must be observed. This adapter is not suitable for the Ford Bronco transfer case as it is of an entirely different design in attachment and drop.

Transfer Case Input Gear

dana_18_20_input_gearOur adapter shaft is splined for six spline input gears.

  • Six-spline gears (shown, right) are most common and usually found behind Jeep T84, T90, T86, T89, T98, T18, T15 & T150.
  • The ten-spline version was only available 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 and Saturn type overdrives are compatible with this conversion as long as the spline count is correct. We do not have replacement gears for the overdrive version.

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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.

Related Products

Novak’s RM103 mount is optional, but highly recommended. As shown in the photo it is a strong and easy way to attach the rear mount. Hard mounting is not acceptable. If you don’t have other plans then this really is an essential part.

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Dana 18 & 20 6 Spline Input Gears

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Transmission Tunnel Cover

Because the transmission and transfer case shifters are often in a different location than factory in these Jeeps, this new transmission tunnel cover gives the installer a clean slate. There are no screw holes nor transmission & transfer case shifter holes, allowing the installer to drill and cut them as necessary. An easy way to get a perfect fit is to use the old cover as a template, making cuts as necessary, then overlay on the new aluminum piece for perfect holes.

The finish is natural brushed aluminum, which looks pretty terrific, but it can easily be primed and painted to suit, if desired.

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D20 Transfer Case Shifters

The stock transfer case shifter may be used, possibly requiring minor modifications. On the Dana 20 it is often advantageous to use a new twin stick style shifter, especially if you are able to remove the interlock pins during the transfer case rebuild process. Multiple models are available depending on your original transmission mated to the D20. It is also possible to retrofit a longer length shifter by using our replacement tubing and TX20-COM4 sold below. You will likely need to re-bend the shifter levers for correct positioning but this gives a sound starting point. Going this route allows the shifter to be positioned further forward in relation to the transfer case which allows a location closer to stock as the transfer case moves back with the longer length TH350.

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This is the tubing necessary to fabricate a custom length shifter, sold by the inch.


All would require the

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D18 & D20 Rebuild and Gasket Options

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Gasket and seals kit

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Dana 20 Billet Pan and PTO Cover

These rigid and precisely machined billet bottom pans are the answer to a few Dana transfer case dilemmas. The thick, smooth-finished flange replaces the thin, warped factory pans and they virtually assure a drip-free seal. The PTO cover does the same for the back, plus they add a little “bling” to your case.

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Dana 18 & 20 3.15:1 Upgrade Gearset

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Transmission Shifters for the TH350

Your TH350 will require a shifter assembly to work properly. If equipped with an automatic shifter on the column and you would like to keep that method of shifting, we recommend this kit:

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We also offer two cable shifter kits that work well. This will be best determined by your personal preference depending on the Jeep it is going in, certain shifters work better. We have special brackets for the TJ to accept a special shifter version in the console. Other quality shifters made for the TH350 will also work well. We have found that the cable versions are usually easier to install and position correctly.

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Transmission Cooling

Transmission Cooling is critical to the life of all automatic transmissions. Conventional in the radiator tank coolers are simply not adequate for long life on a Jeep’s transmission. Here are the products we recommend for best performance and ease of installation.

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Installation Requirements

Tools

Tools required will vary depending on which kit is selected. The automatic transmission takes more specialized tools, knowledge, gaskets, seals, snap ring pliers, etc. The adapter requires typical mechanic's hand tools.

Transmission Output Shaft Length

The 4x4 version output shaft needs modification as follows: 

  • Dana 20 version: The installation of this adapter kit requires that the GM output shaft be cut shorter by 1-1/4 ". 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: 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.

Placement

Transmission placement is largely determined by factory engine location. It is not necessary in typical conversions to change the engine position unless an engine is being swapped in at the same time as will often be the case with these kits. Setting the powertrain to the proper factory or conversion pitch angle - usually tilted down ~5 (3-7 acceptable) degrees - is recommended. Consult our engine conversion guides for more specific recommendations on placement if the engine is being replaced.

Clocking Information & Driveshaft / 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. 

Engines & Engine Mounting

If converting to a V8 in conjunction with this upgrade, aftermarket engine mounts are available to ease its installation. Because of the broad spectrum of engines and vehicle combinations used with this adapter, it would be difficult to list them all here. Whatever your application, Novak likely has the perfect solution. From a 225 Buick V6 in a CJ2A to an LS3 in your JK we’ve got you covered.

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Novak's 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. 

Engine placement in these applications is an effort in compromise to find the best position overall as a package. Generally the engine will be about 1” or even more towards the left, (driver’s side in the USA) away from the front differential in a CJ application. This gives the best balance of weight and more importantly clearance for the driveshaft going to the front axle. Your tight spots will be steering to exhaust on the left (hold that as tight as you can) and clearance for the front driveshaft on the right. Fore and aft position will vary with the Jeep model and engine. Have a CJ5 and Gen I with a rear distributor? You’ll be better off a little forward for more rear driveshaft length and clearance for that HEI. If you are in a longer Jeep and using an LS engine with no distributor, you’ll have more fan clearance and better balance if you hold it to the rear. Usually for ground clearance tuck things up nicely for height to avoid damage to oil pans and other life giving parts in the Jeep. Common sense and taking a step back to look at things overall goes a long way.

Driveshafts

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 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, usually to the detriment of the project. Our recommendation is to always value the correct position of drivetrain components over saving a few dollars which is usually regretted in the long run with compromised positioning. Sometimes the application allows use of the existing shafts without modification. While that is perfectly acceptable, it should not be the first priority. 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. Novak can also accommodate your needs on this if provided with dimensions for the shafts at a reasonable rate.

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.

Also See