Novak's TH400 transmission to the Jeep Dana 300 or Early New Process transfer case conversion makes for one of the strongest geartrains possible for both on-road and off-road, and it remains one of our most requested automatic transmission to transfer case combinations.
The Novak TH400 to Jeep Model 300 / FSJ NP transfer cases adapter is very compact at only 1.4" in length. This adapter assembly is the shortest Turbo 400 adapter in the industry, providing a combined transmission and adapter length of only 25.9" (equivalent to a 18.9" manual transmission / bellhousing combination). The adapter itself is machined of a 6061 billet aluminum alloy, featuring thick flanges and a heavy cross-section.
Billet adapter housing, transfer case input or transmission output depending on kit selection, seal, transfer case to adapter gasket, transmission to adapter gasket, fastening hardware, steel mounting base, and instructions.
AMC Jeep style transmissions from 1976-1979 featured a tilted transmission case casting, and for this we make an optional "R" variation. This adapter configuration is unique on the market in that it levels the adapter's base foot for square mounting on the rear isolator mount and crossmember. This is useful in that the adapter allows installation without clocking your transfer case down, or having your transmission mount sit crooked. Customers should choose this version only for AMC TH400s of the above era. Earlier Jeep units featured "universal" cases that were level as conventional. These earlier cases are identified by their use of a factory 400 transmission to Buick or AMC engine block adapter.
All versions and years of the TH400 can be adapted to the Dana 300 and NP (New Process) transfer cases. Chevrolet, Buick/Oldsmobile/Pontiac, Universal versions all work equally well. Many manufacturers sourced the TH400 from GM; even companies like Ferrari and Jaguar used them. 2 or 4WD versions all work equally well with the correct adapter option.
The 134-A adapter is compatible with all versions of the TH400. If you have a 2wd TH400, a 4wd TH400 that is undergoing a rebuild anyway, are unsure what TH400 you have (or will have at the time of the conversion), or your D300 was just rebuilt (doesn’t leak) and you’d rather not open it back up, then the 134-A kit is your best choice. The new 23 spline TH400 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 300 transfer case. 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. This is a good time for a more thorough master rebuild and update of the Hydra-Matic. 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.
One 4wd version of the TH400 is ready to bolt up to our 134-B adapter kit. Disassembly of the transmission is unnecessary as the 32 spline 4wd style output shaft is correct for this kit version. Partial disassembly of the transfer case is necessary to install a new matching 32 spline Dana 300 input shaft machined from triple-alloy gear steel which provides a superior upgrade.
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.
The NP203 version of the TH400 output shaft features a very short 32 spline sections measuring 1-1/4”. The extended length Novak input shaft engages this shaft perfectly. No other TH400 output shaft is compatible with this kit.
One 4wd version of the TH400 is ready to bolt up to our 134-C adapter kit. Disassembly of the transmission is unnecessary as the 32 spline 4wd style output shaft is correct for this kit version. Disassembly of the transfer case is necessary to install a new matching 32 spline NP input gear.
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 superior quality NP208 master rebuild kits along with a top quality chain are the perfect solution for the job and are available below.
Jeep New Process 208, 219, 228 & 229 transfer cases use the same output shaft style adapters as the Dana 300. Used in 1980+ full-sized Jeep applications, they may be retained using these adapters and are fully compatible using the output shaft version. The simpler and more reliable NP208 can be a particularly worthwhile swap.
Our usual recommendation is to replace the older style transfer case (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. Also the 242 full-time case (particularly the AMG version as it is extremely strong) has the correct side drop and allows a mechanical speedometer output. Certain part-time Dodge 241 applications will also work. These more modern transfer cases allow the use of our cable shifter assemblies for a cleaner installation, have lower low range ratio, helical cut gearing, fluid pump, and are a newer more refined design. Read more about the differences here.
Drivetrain Length & Compatible Jeeps
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 and similar length Jeeps 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.
Any engine that can be made to work with the TH400 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. Yes, it would be possible to put that Jag or Ferrari engine in your Cherokee Chief. Not sure of the practicalities of it, but it would be possible with this adapter.
This transfer case adapter's design is based on Novak's Universal Series adapters that feature a modular mounting and support system. Included with the adapter kit is a steel base that is a highly configurable mounting foot, and is ready to accept our 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.
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
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.
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.
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.
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.
These good used 4x4 output shafts are available for those needing or wanting to go that route with your build up.
If your input is worn or you would like a new input shaft with longer spline engagement to match your Novak output this part is an excellent choice.
Tools required will vary depending on which kit is selected. The automatic transmission takes more specialized tools and knowledge, gaskets, seals, 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.
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.
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, 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.