Turbo Hydramatic 400 Transmission
Jeep Dana Model 300 Transfer Case
Our TH400 to Dana 300 conversion makes for an absolutely strong and capable assembly 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 / 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 from a billet of high-grade aluminum alloy, featuring thick flanges and a heavy cross-section.
These kits are for all years and versions of the popular HydraMatic 400, including Chevy, Buick and other GM, AMC Jeep, etc. and work with 2wd & 4wd versions.
Transmission Output Shaft
Every #134 kit comes with a new output shaft for the TH400, whether for 2wd or 4wd transmissions. 2wd versions work equally well as 4wd versions. The Novak output shaft is of an alloy steel, precision splined and hardened for a superior interchange. This shaft connects the TH400 output direct to the existing 23 spline Dana 300 input shaft for the strongest combination. Installation requires disassembly of the transmission main assembly, and we recommend the services of a transmission professional. The basic installation is 3-4 hour bench job and may include simple gasket and seal replacements. Some choose this as the time for a more thorough master rebuild and update.
|AMC Jeep style transmissions from 1976-1979 featured a tilted transmission case casting, and for this we make an optional variation of our #134 kit. 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 thier use of a factory 400 transmission to Buick or AMC engine block adapter.|
Transfer Case Input Shaft
The included Turbo 400 output shaft splines in directly into the OEM Jeep Dana 300 input shaft, and transfer case disassembly is not required.
It is not requisite that you rebuild your Dana 300 to successfully complete the conversion, but it may be a good time to do so if your transfer case leaks or has many miles of service. We've made our Dana 300 gaskets & seals kits and our all inclusive master rebuild kits available for this purpose.
Transmission Rear Mount
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 (below). This is our preferred rear mount unit. Our #134 kits are designed for it, and its usage is essential to protect powertrain components from the flex and jar typical of any automobile, but especially Jeeps.
Whether you are assembling onto a stock cross member / skidpan or if you are setting up a high-clearance skid plate, you will find it to be a clean and simple process.
Transfer Case Shifter
This transmission conversion will allow for the retention of the factory shifters, or allow you to upgrade to a twin-stick or other known aftermarket shifters.
A broad variety of transmission shifters are compatible with this conversion, ranging from console shifters (i.e.; Art Carr, B&M, etc.), to direct-mount stick shifters (i.e.; Gennie, Lokar, etc.).
Transfer Case Clocking
The adapter features an integrated transfer case clocking / rotation flange that allows the installer (driveshafts permitting) to choose the best angle for the Dana 300 from near-factory (20 degrees down) to near-flat (3 degrees down). However, transmission pan clearances and front axle width may inhibit the flatter options. No purchase of a separate clocking ring - and the associated additional expense and geartrain length - is required.
Use of the factory diameter 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 an AMC TH400 or a GM TH400 using our #437-AMC adapter kit, your factory engine should already have this proper offset.
|The length of the Hydramatic 400 makes its placement into an 80" wheelbase Jeep (CJ5) prohibitive, but is an excellent fit into CJ7s, Utility Series Trucks and Wagons, as well as all of the Full Size Jeeps.|
Driveshaft length changes are often required, as this geartrain combination is typically longer than factory Jeep combinations. However, some GM engine installations will allow for the transfer case to remain in its OEM location.
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, sometimes to the detriment of the project. Driveshaft modifications are usually inexpensive when performed by driveline, RV or tractor implement specialists. New driveshafts are an option but seldom a requirement in regards to the actual successful conversion. Jeeps that require extensive travel or specialty-built driveshafts have this option available through several fabricators across the nation.
For every 10 degrees cooler you can keep the transmission, you can add 25,000 miles to its service life. Therefore, use of a transmission oil cooler is advisable for this automatic transmission. Use of a transmission temperature gauge is also a good idea. These are widely available and generally inexpensive.
With the increase in popularity of the newer, hotter burning, fuel-injected engines, it is increasingly wiser to run a stand-alone, dedicated transmission fluid cooler.
Engines & Engine Mounting
A TH400 installation is often done in conjunction with an engine conversion into the Jeep. These engines include the Chevrolet Small Block V6 & V8, from Generations I, II, III & IV, 1955-2013+.
|Novak's MM Series 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.|
In any scenario, it is critical that the engine be installed (as the Jeep engines usually are) with an offset of 1" to 1-1/2" to the driver's side. Other engine mounts on the market - especially the bolt-in versions - do not take this into account and make other placement decisions for the installer that do not take the full powertrain into account. Novak offers what we have found to be the most intelligent engine mounting system for Jeeps available, allowing the installer to make an easy and satisfying decision as to powertrain placement with the TH400 and the Dana 300 both considered.
|Advanced computer modeling methods were integral to the design of our #134 adapter assembly. We were able to push the bounds of product and process well beyond the status quo.|
Use of factory axles is completely acceptable with this conversion. Axle upgrades are not necessary to the conversion itself, but they may be chosen for reasons external to this transmission upgrade.
The TH400 is a prime building block to an indestructible Jeep powertrain, offering also GM engine compatibility and good parts and service availability.
|32 Spline Input / Output Shaft Mythology
We've seen companies offer a 32 spline output shaft for the TH400 to Dana 300, purporting greater strength. In 28 years and thousands of customers later, our 23 spline TH400 shafts have no reported failures. No breaks, twists, shears, etc. This is due to great manufacturing and smart planning. The installer should consider two things: