AMC I6 & V8 Engines

to the

Chevrolet & GM Hydramatic Transmissions

Widely considered to be the best automatic transmissions in the world, General Motors HydraMatics make for outstanding upgrades into Jeep powertrains. This adapter assembly brings the Jeep / AMC 232, 258, 304 & 360 engines together with Chevrolet style automatic transmissions, including the TH350, TH400, TH700R4, 4L60, Early 4L60-E* and 4L80E transmissions.

The Adapter

This plate style adapter is precision laser cut and machined. Dowel locators and fastening points assure total concentricity for long transmission life. The adapter is plated in black zinc for corrosion resistance and appearance.


Kit contains: zinc plated adapter, flexplate, flexplate reinforcement ring, flexplate spacers, dowel locators, crank spacer, a shield plate with a convenient access port for your torque converter bolts, hardware, and instructions.

Compatible Transmissions

The Chevrolet style HydraMatic transmissions, including the:

  • TH350
  • TH400
  • TH700R4
  • 4L60
  • Early one piece case 4L60E*
  • 4L80E‡

*The electronically controlled early 4L60E and the 4L80E will require a transmission control unit, which - while effective - can be expensive. The installer could consider the conventionally controlled 700R4. In the case of the 4L80E in a Jeep seeing truly hard service, it may be well worth the extra expense.

‡ The 4L80E can be compatible with this kit, but only if the installer procures a modified factory 4L80E torque converter that features the TH350 pads / bolt pattern for the provided flexplate. AMC flexplates do not have the diameter required for the large hole / pad pattern native to the factory 4L80E.

The later style 4L60E (removable bellhousing, hex rear bolt pattern) are not candidates for this conversion.

The TH350 is the only candidate for 1972-1983 CJ5 Jeeps due to their length, and these Jeeps must not have excessive lifts.

Adapting AMC Engines to GM Automatics
  • Kit 437AMC-1, adapting the AMC I6 engines to GM HydraMatic transmissions

  • Kit 437AMC-2, adapting AMC 304 engines to GM HydraMatic transmissions

  • Kit 437AMC-3, adapting AMC 360 engines (1972-1987) to GM HydraMatic transmissions

  • Kit 437AMC-3B, adapting AMC 360 engines (1988-1991) to GM HydraMatic transmissions

  • Kit 437AMC-4, adapting AMC 401 engines to GM HydraMatic transmissions

Compatible Engines


All 1972-on AMC engines, including the:

  • 232 (1971 & later)
  • 258
  • 304
  • 360
  • 401

*NOTE: Some AMC engine cranks were inconsistent in their flange stickout from the engine rear face. Typical AMC I6 and V8 crank flange protrusion from the rear block should be just over 1/2". Some non-standard cranks are nearly flush with the rear block face and in some cases used a crank spacer from the factory to make up the discrepancy.

Because many AMC engines are assembled from varying on-hand parts and because the above-mentioned spacers occasionally get lost, your engine may not conform to this Novak conversion kit and custom work may be required.

On some V8 installations the passenger side exhaust flange on rear-dump manifolds or headers may interfere slightly with the transmission flange in a small area, so deburring this flange may be necessary for your installation.

A TH350 married up to a 258 engine. It offers a lighter, stronger, and cooler running transmission than factory options. The 700R4 and TH400 are also great candidates.

Torque Converter

The majority of these transmission torque converters have the standard size three-bolt pattern that is 10.7" in diameter. Some factory or aftermarket heavy-duty TH400 and 4L80E torque converters, often seen in RV and heavier truck applications, may use a larger bolt pattern diameter or 6 bolts which is not compatible with our flexplate included with this kit. you may exchange this converter towards one with the standard diameter bolt pattern. The transmission portion of the TH350 and TH400 are identical and interchangeable. 4L80E converters are available in the smaller pattern as well. The converter can be rated at any duty or stall you wish.

Installation Requirements

Transmission Shifters for the TH350

The installer can consider a handful of shifters, such as those by Lokar, Winters, B&M and Gennie. They come in a variety of styles and your research on them is encouraged. We've used many Lokar floor shifteres, both direct linkage and cable style.

We often use the #ACA-1802 (see Related Products, below) shift arm to set up hard linkages, using off-the-shelf threaded rods and beaing ends when retaining an existing Jeep column shifter. They can also work with factory cable shifters. Aftermarket cable shifters and add-on column shifters already come with this arm or one similar, so know your options.

The adapter installs onto the engine, then transmission. The installer will need to pay attention to the flexplate-to-torque converter spacing and shim as appropriate (shims included). Instructions are provided.

you will use your existing AMC starter. Some adaptations require a different version of the AMC starter. Refer to the instructions provided.

Related Products

Auto transmission cooler

Engines & Engine Mounting

GM Engine Mounts for JeepsIf 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 Drivers Drop

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 right, (passengers’s side in the USA) away from the front differential in a Wrangler or similar application. This gives the best balance of weight (and more importantly clearance) for the driveshaft going to the front axle. Clearance is usually quite good in these applications; both the steering and front driveshaft push things towards 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 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.

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