This conversion kit joins the popular AX15 and NV3550 overdrive transmissions to the series of AMC bellhousings made between 1976 and 1986 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 effective.
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.
Included are the adapter, bearing retainer (which serves as a centering index for the 76-86 AMC bellhousing and clutch release bearing sleeve) and required hardware.
This adapter assembly is compatible with the following AMC bellhousings:
The Jeep T150/T18 Bellhousing
If you don't have one of the above bellhousings, but have the factory 1994-2004 4.0L to AX15 / NV3550 bellhousing, Novak recommends this installation method.
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.
AMC I6 & V8's
All AMC engines made from 1972-2006 are compatible with the above bellhousings and therefore this conversion, including the 232, 258 & 4.0L I6 as well as the 304, 360 & 401 V8's.
The Jeep / GM Iron Duke 2.5L bellhousing is also compatible with this conversion; some ancillary pieces will vary a bit but the adapting process is the same.
The factory flywheels on all of the above engines are acceptable. Most will accept the recommended 10-1/2” clutch. There are instances of larger clutches in some trucks. If you have one of these applications the clutch diameter will need to match. The Iron Duke will also need the clutch matching its flywheel.
Novak’s hydraulic release slave cylinder kit.
The factory pressure plates, whether three-finger or diaphragm, are compatible with this adaptation. However, 1976-1979 (T150 & T18) clutch disc hubs have a 1-1/16" spline diameter that is not compatible with the 1-1/8" input shafts of the AX15 & NV3550. The proper clutch disc will be required and can be purchased separately below, or combined with a new pressure plate.
The factory clutch release arms and their linkages can be retained, including mechanical bellcrank style linkages, or hydraulic clutch release systems, whether factory or aftermarket retrofit.
All versions of the AX15 & NV3550 are compatible. However, 1994 and later AX15's and all NV3550s will require a minor modification to their input bearing retainer. Earlier AX15s that featured the concentric internal throwout slave bearing do not require this modification. This is also compatible with Novak’s new, upgraded, stronger AX15 transmissions which come assembled to the extent possible with all parts ordered together. 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. Adapter thickness is just under 1” and the transmission is 16.5” long giving a 17.5” overall length from the front face of the adapter to transfer case mounting flange. The OEM AX15 bellhousing and associated shaft stickout of 7.5” is 1” longer than a standard 6.5” AMC bellhousing which lines things up perfectly with the adapter plate installed giving standard dimensions to the front of the adapted assembly. 10 input splines at 1-1/8” diameter and a pilot diameter of either .59 (early) or .75” (late) are accommodated by the correct pilot bushing and clutch specified below.
One of the following Pilot Bushings is required for all installations. Please choose your applicable engine and transmission combination:
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.
This popular clutch assembly from 1980-1986 Jeeps is our preferred kit for holding power yet reasonable pedal pressure. The disc's spline hub features the correct 1-1/8" x 10 spline configuration for these transmissions.
The disc can be purchased separately for those early applications natively using the 10 spline 1-1/16” disc
While usually not needed in this application, it is priceless when clearances dictate its use. 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, do recommend its use. Further information is here.
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:
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.
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.
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.
A drill, 29/64” bit, and various smaller bits are required, in addition to typical mechanic's hand tools.
Note 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.
If converting to a V8 in conjunction with this upgrade, aftermarket engine mounts are available to ease its installation.
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.