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Adapting the
Turbo Hydramatic 350
to the
Jeep Dana Model 300 Transfer Case

Our TH350 to Dana 300 conversion makes for a very strong, and capable assembly both on-road and off-road. It is one of the most persistently popular transmission conversions into Jeeps, providing a very compact geartrain, compatiability with excellent engines and ease of installation.

Turbo 350 Adapter

Kit 135, adapting the TH350 transmission (4wd version) to the Jeep Dana Spicer Model 300 transfer case
Part #: 135
Weight: 11.35
Price: $508.00
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Adapter casting, transfer case input / adapter shaft, seal, gasket, seal ring, fastening hardware, steel mounting base and instructions.
Kit 135-S, adapting the TH350 (2wd version) to the Jeep Dana 300 or Jeep NP208, 219, 228 or 229 transfer cases
Part #: 135-S
Weight: 10.44
Price: $567.00
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Includes: adapter casting, transmission output / adapter shaft, seal, gasket, seal ring, fastening hardware, steel mounting base and instructions.

The Adapter
The Novak TH350 to Jeep Model 300 transfer case adapter is very compact at only 3.1" long for a combined transmission and adapter length of 24.8". The adapter itself is cast and machined of a high-grade aluminum alloy, featuring thick flanges, a heavy cross-section and strength-adding gussets.

TH350 Versions
Any version and year of the TH350 can be adapted to the Dana 300, from Chevy, to Buick / Olds / Pontiac and Unicase versions of the TH350, as determined by your choice of engine.

Option I: Transfer Case Input Shaft Version
4wd versions of the Turbo 350 are all ready to bolt up to our adapter assembly. Disassembly of the transmission is unnecessary as the required style of output shaft is already installed; however, partial disassembly of the transfer case is necessary to install the new input shaft. The 4wd version of the TH350 (all years) uses our #135 adapter kit (above, upper), which includes a new 27 spline input shaft for the Dana transfer case. This shaft is compatible with and splines directly to the OEM 4wd style output shaft that protrudes 3/4" from the rear face of the TH350 transmission main case. The included Dana 300 input shaft is machined from triple-alloy gear steel and provides a superior upgrade.

The input shaft installation is a 1-2 hour bench job and may include simple gasket and seal replacements. It is not requisite that you rebuild your Dana 300 to successfully complete the conversion while installing the new input shaft, 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.

The 4wd version of the TH350 will have a ~3/4" output shaft stickout length.

Option II: Transmission Output Shaft Version
2wd versions work great when you choose our #135-S kit and install the new, included 4wd style transmission output shaft. This included, 23 spline TH350 output shaft is machined from 300M alloy gear steel and provides a superior upgrade. This shaft is compatible with and splines in directly to the OEM style input shaft in the 300 transfer case. This requires disassembly of the transmission, and we recommend the services of a transmission professional. The basic installation is a 2-4 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 of the HydraMatic.

Installers using a 4wd TH350 can also use this #135-S kit, noting that the included transmission output shaft will replace the OEM style 4wd shaft. Individuals that are unsure what TH350 they have (or will have at the time of the conversion) can choose this option.

TH350 4wd output shaft
If necessary, we offer a good, used version of the 4wd output shaft for your TH350


Shaft, output, TH350, 4x4, used
Part #: 8641088
Weight: 4.00
Price: $49.50
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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 (box, left). This is our preferred rear mount unit. Our #135 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.

Jeep transmission crossmember mount
Mount, rear, transmission, polyurethane Chevy, Jeep, Novak style
Part #: RMU
Weight: 1.60
Price: $30.82
Buy:

 

Transfer Case Shifter
This transmission conversion will allow for the retention of the factory shifters, or allow you to upgrade to a twin-stick shifter.

Transmission Shifter
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.).

Novak adapter with Lokar shifter

 

A broken, friction-welded shaft
We’ve seen a handful of shafts broken like this one, and heard our customers speak of more failures of output shafts made by other adapter companies. This is why we go through the trouble and expense of making our output shafts from a solid bar of exceptionally strong 300M alloy steel, instead of lower grade alloys or friction welding salvage GM shafts. A second, sometimes less obvious but pernicious problem is the issue of warpage during friction welding and heat treating - which cannot be corrected when the shaft journals are already ground and worn at or below factory specifications.

The Novak shaft in our #135-S kit is produced faithfully to factory specifications, and using even better steel. Our 4-axis CNC cut of the spiral gear and other features are no small tasks, and likewise, no small benefit to our customers dedicated to putting their Jeeps together right.

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.

Driveshafts
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.

Installers should note a possible benefit of the TH350 - usually done in conjuction with a Chevy Small Block engine conversion - of possibly not having to change or modify driveshafts in some 1980-1986 CJ Jeeps. The TH350/Novak adapter combo is about 3" longer than the stock SR4, T4, T5 transmissions. However, most Chevrolet engines install 3 or more inches ahead in the engine bay, offsetting that difference.

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.

TH350, adapted to a Dana 300

 

Transmission Cooling
Transmission Oil CoolerFor 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.

A complete, adapted TH350 ready to ship
A turn-key TH350, professionally built, adapted and delivered to your door - ready for a variety of engines and Jeep transfer cases. Read more...

 

Engines & Engine Mounting
A Turbo 350 installation is typically done in conjunction with an engine conversion into the Jeep. These engines include the Chevrolet Small Block V6 & V8, from Generations I, II, & III, 1955-2006.

Novak's Jeep Motor Mounts
Novak's MM Series 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.

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 consideration. 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 TH350 and the Dana 300 both considered.

A digital model of our TH-350 adapter
Advanced computer modeling methods were itegral to the design of our #135 adapter assembly. We were able to push the bounds of product and process well beyond the status quo.

 

Axles
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.

 

Turbo 350 to Jeep Dana Transfer Case