Adapting the

GM 6L80E Transmission

to the

Jeep Dana 300 Transfer Case & FSJ NP Transfer Cases

Novak's 6L80 & 6L90 transmissions to the Jeep Dana 300 & FSJ New Process 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 Novak 6L80 / 6L90 to Jeep NP / NVG transfer cases adapter is compact at 3-1/4" long for a combined transmission and adapter length of 26-1/2” for the 6L80 and 27-3/4” for the 6L90 (equivalent to a ~19-1/2” or 20-3/4” manual transmission). The adapter itself is machined of aluminum alloy, featuring thick flanges and a heavy cross-section.

Dana 300 Version

Adapter kit for 6L80E to Jeep transfer cases

Kit 6L83-B, adapting 6L80 transmissions to Jeep Dana 300 transfer cases

The Dana 300 version of this kit comes with a new 32 spline input shaft that will require disassembly of the Dana 300 input assembly. The input shaft installation is a 1-2 hour bench job and usually includes either a simple gasket and seal replacement or a rebuild if you belive your transfer case is due. Bearings and pre-load are involved with the input service job. We do sell a 300 input service kit that includes a new bearing retainer, bearing, seal, and shims - and we'll set it all up for you and press your new input shaft into it if you order them at the same time. See Related Products, below.

Novak also has Dana 300 gaskets, a premium master rebuild kit and various other parts at the ready. See Related Products, below.

The adapter kit contains:

  • Adapter housing
  • Transfer case input shaft
  • Transfer case to adapter gasket
  • Transmission to adapter sealing ring
  • Fastening hardware
  • Modular steel mounting base
  • Instructions

New Process 208, 219, 228 & 229 Transfer Cases Version

Adapter kit for 6L80E to Jeep transfer cases

Kit 6L83-C, adapting 6L80 transmissions to Jeep Full-Size NP208 transfer cases, input gear version

The FSJ NP version of this kit comes with a new 32 spline input gear to replace the 23 or 31 spline input gear from the factory. This will require disassembly of the transfer case, which is a few hours as a bench jo 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 adapter kit contains:

  • Adapter housing
  • Transfer case input gear, 32 spline
  • Transfer case to adapter gasket
  • Transmission to adapter sealing ring
  • Fastening hardware
  • Modular steel mounting base
  • Instructions

Applications & Compatibility

Note that with the exception of transmission length and output spline count / diameter, all of the information discussed herein applies to both the 6L80 and 6L90 transmissions. Some references may be made to "E" suffix transmissions in various places (e.g., 6L80E), but GM refers to them without it, as all their transmissions are now 'E'lectronically controlled.

Compatible Transmissions

There are two versions of the 6L80E transmission output shaft that will work with the Novak adapter. The 4wd version 6L80 is ready to bolt up to our 6L83 adapter kit. The stock 2wd truck version will work with by cutting the output shaft off with a separating disc. Once the output shaft is shortened 3/4", this 2wd version 6L80 is ready to bolt up to our 6L83 adapter kit. Disassembly of the transmission is unnecessary as the 32 spline 4wd style output shaft which protrudes about 3" from the rear face of the 6L80E transmission main case is correct for this kit version.

Other 6L80 versions require the output shaft of the transmission be replaced with the short 4wd version and the rear of the unit sealed.

The 2wd style output shaft, shortened

Jeep New Process 208, 219, 228 & 229 Transfer Cases

Because of parts availability and comparative reliability issues, We've been known to recommend replacing the older style FSJ New Process transfer cases (like the 219, 228 and 229) with a newer, more modern version such as the part-time 231J with HD SYE kit installed and upgrades as appropriate.

However, if you like your transfer case is in good condition, then move forward with the conversion.

Compatible Jeeps

This conversion is compatible with all longer wheelbase (CJ7 93.4” 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 1/2 and 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.

Compatible Engines

Any engine that can be made to work with the 6L80 will work with this adapter. Natively compatible engines such as the 2006+ Vortec / LS / Gen III+ engines are good choices. The nature of GM Generation IV communications to run the 6L80 is complex, given the networked CAN bus and keyed TCM (or TECM) and only an ECM and TCM which are specifically coded to each other are compatible. Therefore, the following three options are available:

  • Run a matched ECM & TCM set pulled from the same donor vehicle
  • Have a specialty programmer or GM recode a GM ECM & TCM pulled from different donors
  • Run an aftermarket 6L80 controller. Brands such as Zero Gravity, Holley, TCI & PCS may work for your situation.

Lastly, be aware of Gen III engine crank spacing 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.

Transfer Case Clocking & Rotation Options

Our adapter is drilled for multiple clocking locations ranging 23 degrees. However, most New Process chain drive transfer cases will favor near factory clocking.

Rear Mount Provision

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.

Related Products

Spacer for 6L80 6L90 transmission
Urethane Rear Mount for Crossmember
Auto transmission cooler
Dana 300 twin stick shifter
1976-1986 Jeep floor tunnel cover
Dana 300 Rebuild Kit
6L80E cooling lines AN adapter
6L80 rear seal kit
Billet aluminum Dana transfer case pan
Dana 300 Super Short Tailhousing
TurnKey 6L80E Transmission Package

Installation Requirements


The New Process transfer case requires hand tools, large snap ring pliers and RTV to reseal. Rebuilds are a little more involved but not much.

Engine Placement

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.

Clocking Information & Driveshaft to Pan Clearance

Our adapter is drilled for multiple clocking locations and driver’s side drop transfer cases usually clear nicely in most all applications.

Engines & Engine Mounting

GM Engine Mounts for JeepsNovak 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:

  • Left-right offset location is similar to factory at ~1-1/4" to the driver's side
  • Avoid installing the engine too low (axle clearance and other issues)
  • Avoid installing the engine too high (transmission tunnel interference, etc.)
  • Set your engine to 4-7 degrees of tilt rearwards, like the factory engine & powertrain
  • It is usually best that Chevy and Gen III+ V8 engines install approximately 3" further forward, using the back of the engine block face as the datum
  • When mocking up your engine installation location, pay special attention to radiator and fan clearance.
  • Firewall modifications are not expected.

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 “CV style” rear shaft with the correct geometry at the axle to minimize vibrations and possible binding.

Also See