Adapting the

Chevrolet & GM Standard Shift Engine Bellhousings

to the

Jeep AX15 & New Venture 3550 Transmissions


This conversion kit joins the popular AX15 and NV3550 overdrive transmissions to the standard GM pattern bellhousings for a variety of OEM transmissions. This affordable and straightforward method allows the installer to retain the bellhousing they already own, and in many cases, the existing clutch and its release system. Its implementation is simple and extremely effective.

Product & Features


The adapter is precision designed and expertly CNC machined from 6061 T6 aluminum. Its thick cross-section provides ample thread engagement and high structural integrity. Precision indexing is achieved through locating dowels to the transmission and bearing retainer to the bellhousing.


Include GMAX15 adapter plate, bearing retainer (which serves as a centering index for the GM bellhousing and clutch release bearing sleeve) and required hardware.

Applications & Compatibility



Chevrolet Gen I/II bellhousing showing the appropriate pattern for the GMAX15 adapter

This conversion is compatible with CJ7 and longer Jeeps. CJ5 Jeeps do not have a long enough wheelbase for the longer, five-speed transmissions.

These are strong transmissions, and full Size Jeeps such as Wagoneers, J-Trucks, etc. are conversion candidates for them unless used for more aggressive driving or heavy work situations.


Nearly all GM Generation I-III engines are compatible with this conversion, including Chevrolet Small Blocks, Gen III+ V8's, Chevrolet V6's and Chevrolet I6 engines. Buick, Olds, Pontiac, and other GM engines are compatible with this adapter assembly if you have a standard shift classic GM bellhousing and flywheel for your engine. Even some of the front wheel drive and odd application engines could be made to work with this adapter using certain factory or aftermarket bellhousings sharing this common rear pattern.


The factory flywheels on all of the above engines are acceptable with some notable exceptions. The LS architecture (Gen III & IV GM V8) engines have a crank offset of 0.400” forward that necessitates a special flywheel available below. There are a few rare exceptions to that rule in the 4.8L & 6.0L engines (from the heavier 3/4+ ton truck applications) to be wary of as they are special cases in themselves and very specific in their flywheel requirements. The 400 small block and some Gen II examples are externally balanced and require special consideration. Make sure the flywheel matches the engine, fits in your bellhousing and will accept an appropriate clutch.


hcrc_top_rear_quarterThe factory pressure plates, whether three-finger or diaphragm, are compatible with this adaptation. However, the clutch will need to match both the flywheel and be compatible with the bellhousing. Not all bellhousings and flywheels will accept the larger clutches. 153 tooth flywheels are limited to the more difficult to source 10-1/2” clutch and changing over requires the appropriate bellhousing, flywheel, clutch and starter. Our advice is to plan ahead and not get stuck with difficult to source parts simply because you may have one piece of the puzzle.

The factory clutch release arms and their linkages can often be retained, including mechanical bellcrank style linkages, or hydraulic clutch release systems, whether factory or aftermarket retrofit.

Transmission Versions

ax15_transmissionAll versions of the AX15 & NV3550 are compatible. However, 1994 and later AX15's and all NV3550's will require a minor modification to their input bearing retainer. Earlier AX15's that featured the concentric internal throwout slave bearing do not require this modification.

This is also compatible with Novak’s new and upgraded, stronger AX15 transmissions which come assembled to the extent possible with parts ordered. They can be seen here and purchased below.


The adapter is precision designed, and expertly CNC machined from 6061 T6 aluminum. Its thick cross-section provides ample thread engagement and high structural integrity. Precision indexing is achieved through locating dowels to the transmission and bearing retainer to the bellhousing.


Include GMAX15 adapter plate, bearing retainer (which serves as a centering index for the GM bellhousing and clutch release bearing sleeve) and required hardware.

Related Products

Pilot Bushing

One of the following Pilot Bushings is required for all installations. Please choose your applicable engine and transmission combination:

Transmission Rear Mount

The AX15 and NV3550 feature a threaded base for support and isolation of the transmission and transfer case. Factory style isolator mounts are difficult to work with in any situation other than as a direct factory replacement. Novak has engineered a universal style rear mount that is easy to affix to a variety of Jeep crossmembers and is very strong and highly adjustable. We recommend it in any retrofit situation. More info on this mount can be seen here.


LS flywheel

This is a beautiful piece and necessary for proper operation on LS based engines. They must have the LS crank offset to work properly. These will accept both the 11” and 12” clutch listed below. The page is here with details.


Bolts necessary for installation


Clutch Kit

Many common GM applications used the 10 spline 1-1/8” hub and as such, it is usually a matter of selecting the correct version. Three sizes are listed below. Most common is the 11” listed in the middle but all are serviceable depending on your needs. Generally the 10-1/2” is used on the smaller 153 tooth flywheel and is exclusive to that application. The 11” and 12” are usually interchangeable with large bellhousings and standard 168 tooth flywheels. Non-standard applications will need to watch for compatibility.


The disc can be purchased separately for those applications natively using a different spline count


Adjustable release bearing

While sometimes not needed in this application, it is priceless when clearances dictate its use. You may get lucky and find a correct height release bearing but this product will guarantee correct height when set up properly. Further information is here.

While sometimes not needed in this application, it is priceless when clearances dictate its use. With all the variabilities in flywheel and clutch height, we highly recommend its use. Further information is here.


And adjustable pivot is an additional noteworthy option allowing even more flexibility to this critical setting.


Bellhousings and adapter rings 

Most stock bellhousing will work with the GMAX15. Large 5-1/8” bore versions require a ring to adapt to the 4-11/16” size of the GMAX15.


If you need a bellhousing, would prefer a new enhanced casting version or would like the LS specific version they can be purchased here:

Chevrolet pattern, Gen I & II small 4 ­11/16” bore

Chevrolet pattern, Gen I & II large 5­ 1/8” bore

Chevrolet pattern, Gen III & IV small 4 ­11/16” bore

Chevrolet pattern, Gen III & IV large 5 ­1/8” bore

Hydraulic Clutch Actuation

Though not required on all applications, now is an excellent opportunity to upgrade from the likely worn mechanical system. These mechanical systems are usually full of play which is aggravated by years of wear and much more affected by flex in the body/frame relationship, especially when in a twist off-road. You will find that your clutch release point will vary as things twist. With a hydraulic system, that is not the case. All flex is taken up by the braided stainless line which is unaffected by changes in frame to body relationship. If your Jeep has the master cylinder, that part can be reused. More information can be found here. Parts to do this swap are:


Transfer Case Adapter


Novak's #153 adapter kit is recommended for joining the AX15 & NV3550 to the popular Dana transfer case as found in 1980-1986 Jeeps. The AX15 can be adapted to the Jeep Dana 20 transfer case using:


Novak's #152 adapter kit. *Warning* Watch closely the overall length of the 152 combination.


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.


Transfer Case Shifter Kits

Many of these transmission retrofits end up in earlier Jeeps and they often require a modified transfer case shifter kit. For the Jeep Dana 300, we recommend the Adjustable Length twin stick kit with these transmissions. The TX300 can be used but is positioned further back and requires modification to the shifters to clear as well as the pan and tub.



Installation Requirements

Installation Requirements 


A drill, 33/64” bit, and various smaller bits are required, in addition to typical mechanic's hand tools.

NV3550 Installation Caveat

gm_to_3550_adapter_quarterNote that NV3550 transmissions have a shift rail boss that protrudes through the adapter, and will require that the bellhousing be milled for clearance. The adapter can be used as a template to mark for this operation.


Transmission placement is largely determined by factory engine location. It is not necessary in typical conversions to change the engine position. Setting the powertrain to the proper factory or conversion pitch angle - usually tilted down ~5 degrees (3-7 acceptable) is recommended.

Engines & Engine Mounting

mmtj-g3If 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. On a driver’s side drop transfer case, usually the later Jeeps, things often get a little easier as steering and front driveshaft are pushing you the same direction. 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 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, usually to the detriment of the project. Our recommendation is to always value the correct position of drivetrain components over saving a few dollars which is usually regretted in the long run with compromised positioning. Sometimes the application allows use of the existing shafts without modification. While that is perfectly acceptable, it should not be the first priority. 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. Novak can also accommodate your needs on this if provided with dimensions for the shafts at a reasonable rate.


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