Adapting the

GM 6L80E Transmission

to the

Jeep Dana 300 Transfer Case & FSJ NP Transfer Cases

Novak's 6L80E transmission to the Jeep Dana 300 or Early 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.

Product & Features


The Adapter

The Novak 6L80 to Jeep transfer cases adapter is compact at only 3-1/4" long for a combined transmission and adapter length of 26-1/2" (equivalent to a ~19-1/2" manual transmission). The adapter itself is machined of a 6061T6 billet aluminum alloy, featuring thick flanges and a heavy cross-section.

Transfer Case Clocking & Rotation Options 

Our adapter is drilled for multiple clocking locations from near-factory (20 degrees down) to near-flat (3 degrees down). However, pan clearances and front axle width may inhibit the flatter options.

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 for purchase below.


Billet adapter housing, transfer case input, transfer case to adapter gasket, fastening hardware, steel mounting base, and instructions.

Applications & Compatibility


There are two versions of the 6L80E transmission output shaft that will work with the Novak adapter. The stock 4WD version will work with a minor modification to the transmission - shortening the output shaft by 3/4". The stock 2wd truck version will work with several modifications done externally. Other versions require the output shaft of the transmission be replaced and the rear of the unit sealed. All years of the 6L80E are compatible with the kits. More specific information on the modifications needed is provided below. 

Once the output shaft is shortened 3/4", the 4wd version 6L80E is ready to bolt up to our 6L81 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. Disassembly of the transfer case is necessary to install a new matching 32 spline input gear.

The input shaft installation is a 1-2 hour bench job and usually includes either a simple gasket and seal replacement or preferably a full rebuild of a tired D300. Bearings and pre-load are involved with this job. It is not requisite that you rebuild your Dana 300 to successfully complete the conversion. However, it is certainly worth consideration especially if your transfer case leaks or has many years of service. Our superior quality Dana 300 gaskets & seals kits and our all-inclusive master rebuild kits with stronger Novak manufactured center pin are highly recommended for this purpose.

If working with an NP208, the input gear installation is a 2-3 hour bench job and usually includes either a simple gasket and seal replacement or preferably a full rebuild of a tired transfer case, especially a chain replacement. It is not requisite that you rebuild your transfer case to successfully complete the conversion. However, it is certainly worth consideration especially if your transfer case leaks or has many years of service. You will be going all the way into the front of the transfer case to install in the input gear. Our NP208 master rebuild kits along with a top quality chain are the perfect solution for the job and, available below.

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

We've been known to recommend replacing the older style FSJ New Process transfer cases (especially the troublesome 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 your transfer case is in good condition, then move forward with the conversion.


Because this is a longer transmission, it is not compatible with most short wheelbase Jeeps if they have much lift, due to driveshaft angles. CJ7's may be feasible if the lift is mild. However, CJ8 Scrambler Jeeps, other longer Jeeps, especially the full sized trucks and Wagoneers are ideal candidates if punishing transmission duty is a prime consideration. 


Because of the complex nature of the communication between engine and transmission on these transmissions we recommend that the native engine be used with its matched transmission. The 6L series transmissions have an internal TCM (transmission control module) and take a signal via the can bus along with other inputs to calculate the best shifts and control. These units use clutch to clutch shifting on all but one of the forward gears and are extremely exact in their control. See our knowledge page linked below for more information. 

While possible, separate control of the 6L series transmissions is a complicated proposition and not something for which we provide support.

Related Products

Transmission Rear Mount

This transfer case adapter's design has a structural base for an industry standard urethane isolator mount, available for purchase. This is our preferred rear mount unit. Our kits are designed for it, and its usage is essential to protect powertrain components from the flex and movement typical of any automobile, but especially Jeeps.

Whether you are assembling onto a stock crossmember/skidplate or if you are setting up a high-clearance skid plate, you will find it to be a clean and simple process.



Some 6L80 output shafts have a long un-splined neck that requires a spacer for the transfer case input shaft splines to mate correctly. Our 163 is a 1.5" thick spacer that allows for these longer shafts to still be adaptable. This spacer locates between the transfer case and your Novak adapter.


6L80E 2WD Seal Kit

Any of the 2WD transmissions need to be sealed up with the following kit that includes the rear seal and necessary plugs. The output will also need to be cut as specified in the instructions to the 4WD length.

D300 Transfer Case Shifter

The stock D300 shifter may be used, possibly requiring minor modifications. Often it is 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. For the Jeep Dana 300, we recommend two twin stick shifters. One features an adjustable length.


Another great option for the D300 is our Dana 300 Transfer Case Twin-Stick Shifter Kit which is a solid, high quality option but lacks the forward adjustability of the transfer case shifters. It has the option of billet knobs showing the engraved shift pattern.



All would require the


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. More information can be found here…



The 6L80E & 6L90E require a special fitting at the transmission to use the braided lines


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.

This tunnel cover is compatible only with 1976-1986 CJ Jeeps.



D300 Rebuild and Gasket Options


Gasket and Seals Kit

Dana 300 Billet Bottom Cover Pan


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.

Two designs are available for the Dana 300: The shallower depth, low-profile version for Jeeps requiring greater ground clearance. This version increases fluid capacity over the factory pan by about 6 oz. The extended depth version that maximizes the fluid capacity for the most punishing service. This version increases fluid capacity over the factory pan by about 16 oz.


 Dana 300 Ultra-Short HD Rear Output Assembly

If you can accommodate the electronic speedometer or don’t need a speedometer option, this kit will give you the ultimate in strength and short length. Full details are here.


208 Rebuild Kit and Chain


Installation Requirements


The automatic transmission takes more specialized tools and knowledge, gaskets, seals and snap ring pliers, etc. The D300 input will require bearings be pulled and pressed on the input, in addition to typical mechanic's hand tools. The 208 requires hand tools, large snap ring pliers, and RTV to reseal. Rebuilds are a little more involved but not by much.


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. Our adapter is drilled for multiple clocking locations from near-factory (20 degrees down) to near-flat (3 degrees down). However, pan clearances and front axle width may inhibit the flatter options.

mmtj-g3Engines & 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.

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.


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 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.

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. 


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