Novak's 4L80E transmission to the Jeep New Process (or New Venture) transfer cases conversion makes for one of the strongest geartrains possible for both on-road and off-road, and has become an increasingly popular transmission to transfer case combination.
The adapter is compact at only 3.0" long for a combined transmission and adapter length of 29-1/4" (equivalent to a ~22-5/8" manual transmission). The adapter itself is machined of a 6061 aluminum alloy, featuring thick flanges and a heavy cross-section.
There are two different styles of kits to join a 4L80E to your New Process transfer case:
The 4L81-A adapter is compatible with all versions of the 4L80E. If you have a 2wd 4L80E, a 4wd 4L80E that is undergoing a rebuild anyway, are unsure what 4L80E you have (or will have at the time of the conversion), are missing the rear speed sensor, or your transfer case was just rebuilt (doesnât leak) and youâd rather not open it back up then the 4L81-A kit is your best choice. The new 23 spline 4L80E output shaft is machined from stock material through an extensive process ensuring maximum strength and a precise fit. The new Novak shaft splines directly into the OEM style input shaft of a 23 spline transfer case. The 241OR Rubicon must use the 23 spline output version. This requires disassembly of the transmission, and we recommend the services of a transmission professional.
The basic installation is a 2-2.5 hour bench job and will include at least simple gasket and seal replacements. Be sure that if your transmission is missing the output speed sensor it is added at this time. See below for the correct parts. This is a good time for a more thorough master rebuild and update of the Hydra-Matic.
In about 1997, GM changed the way the rear bushing is oiled in the 4L80E transmission. The shafts are not interchangeable and you will need to identify for sure which version you need.
There is a factory 4wd version of the 4L80E which is ready to bolt up to our 4L81-B adapter kit. It features a 32 spline output shaft which protrudes about 3" from the rear face of the 4L80E transmission main case. If you have this version, disassembly of the transmission is unnecessary but disassembly of the transfer case is necessary to install the provided input gear.
The input gear installation is a 2-3 hour bench job and usually includes either a simple gasket and seal replacement or a full rebuild with chain if the transfer case has many miles on it. Transfer case rebuild kits are available. See Related Products, below.
The NP/NVG input gears are divided into early and late styles around 1993-1994. There are no guarantees that this change was a clean break pre-1993 vs. post-1993, or that your Jeep's transfer case hasn't been swapped by a previous owner.
If in question, the input bearing width on these models is a good indicator. âEâ Early uses a 24mm wide bearing and âLâ late is 16mm wide. The adjacent photos show the differences in width of the bearing location and the stepped shoulder between the bearing and the gear.
The 241JK transfer case is a late cut gear, requiring a specially machined shoulder, provided if you choose this option in the above kit.
The adapter kit is designed for compatibility with 23 spline Jeep NP207, NP231, NP242, NP249, NP241 & NP241OR "RockTrac" transfer cases. Below is a summary of spline counts and lengths usually encountered.
A more detailed discussion of New Process input gears is found here.
The 21 spline shaft is substantially weaker than the 23 spline version. 21 spline versions were only used in the 4 cylinder applications and some very early automatic 6-cylinder versions. Novak does not make a 21 spline version of this adapter kit because of this weakness, vs. the torque created by this transmission.
Our recommendation is to change the transfer case input gear to a 23 spline version. See Related Products, below.
All versions and years of the 4L80E can be adapted to the NP (New Process) transfer cases. Both the 2WD and 4WD versions work equally well with the correct adapter option.
1991 - 1996 4L80E's should feature a speed sensor at the driver's side rear portion of the case (see image, below), whether they are 2wd or 4wd applications. 1997 and later 4wd applications often omit the rear sensor as this data is available from the transfer case output shaft in factory applications. This adaptation requires that this sensor and its internal reluctor ring be installed by a transmission building professional for proper operation.
See Related Products, below.
This conversion is compatible with all longer wheelbase (CJ7 93.4â or longer) or stretched Jeeps. The TH350 is the only real automatic option practical for CJ5 and other short wheelbase Jeeps.
These are exceptionally strong transmissions native to 3/4 ton truck and SUV applications. Full Size Jeeps such as Wagoneers, J-Trucks, etc. are conversion candidates for them. There are numerous upgrades available for the 4L80E should stock strength come into question.
Any engine that can be made to work with the 4L80E will work with this adapter. Natively compatible engines such as the 1997-2006 Vortec / LS / Gen III+ engines are far and away the most popular choices.
Keep in mind that if you depart 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 youâll only have reverse, third gear and max line pressure; probably not the best solution for a Jeep.
Lastly, be aware of Gen III engine crank spacing, 4L80 flexplates, and torque converter heights. This is not much of an issue where installers have pulled a factory matched engine / transmission combo as their donor, whereas those who are mixing and matching LS components should verify accordingly. We've written a helpful guide to GM crank spacing here.
Our adapter is drilled for multiple clocking locations. However, most New Process transfer cases will clock to a near-factory angle.
This transfer case adapter's design features a modular mounting and support system and mounting base, ready to accept our industry standard urethane isolator mount, available in Related Products, below.
The automatic transmission takes more specialized tools, knowledge, gaskets, seals, and snap ring pliers, etc. Installation after the output shaft is in place requires normal mechanics hand tools.
This transfer case adapter's design features a modular mounting and support system and mounting base, ready to accept our industry standard urethane isolator mount. See Related Products, above.
As these usually are installed as part of an engine swap setting the powertrain to the proper pitch angle - usually tilted down ~5 (3-7 acceptable) degrees - is recommended. Offset will be to the right (passengerâs) side because of the driver drop transfer case and front differential usually 1 to 1-1/2â. Consult our engine conversion guides for more specific recommendations on placement if the engine is being replaced.
Our adapter is drilled for multiple clocking locations and driverâs side drop transfer cases usually clear nicely in most all applications. Yoke and driveshaft clearance is usually ample.
Novak engine mounts are available to ease the installation of your GM V6 or V8 engine. Novak has engines mounts for most Chevy, Buick and GM Gen III+ V8's.
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.
Engine placement in these Jeeps should consider the following points:
Since TJ Jeeps have higher hood clearance, clearance for classic Small Block and high Vortec (truck style) intakes and accessories is not a problem. However, XJ / MJ Jeeps have low hoods and will require the use of lower car intakes and accessory packages.
Novak Gen III+ engine mounts for TJ, XJ, & '76-'86 CJs will remove any guesswork from the engine installation location as they are predetermined for the best location and engine clearance margins.
Driveshaft length changes may be required. Chevy engines (with their rear distributors) can install around 3" further forward than AMC engines. It is also recommended that LS family engines be installed 3" further forward than the factory block (using the back face of the block as the datum point) for exhaust clearance, firewall access, etc.
Because of the engine placement and transfer case SYE kits are frequently installed with many of these conversions, you may end up with a longer rear driveshaft (very desirable for lifted Jeeps) and a shorter front driveshaft.
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.
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 âCV styleâ 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.