The Novak Guide to the

Aisin-Warner AX15 Transmission

ax15_transmissionThe Aisin-Warner AX15 transmission is a very successful, medium-duty, standard shift, five-speed transmission. It was introduced in the 1988 (mid-year) YJ Wrangler and XJ / MJ Cherokee / Comanche Jeeps, and found in 1989*-1999 Jeep XJ, YJ, and TJ models. Its only year in the ZJ Grand Cherokee was 1993, and only with the six-cylinder.

The AX15 is found behind the AMC 258 and the Mopar 4.0L (242 ci) I6 engine. The AX15 is also found in Dakota trucks and is closely related to the Toyota R154 as found in the Supra Turbo, though the case rear halves and gear ratios vary. It is also related to (or referred to) as the AN5, AR5, MA5 in GM and Isuzu applications.

The AX15 was available in Jeeps in both 2wd (typ. XJ / MJ applications) and 4wd versions.

*The AX15 was a mid-year upgrade from the weak Peugeot BA10/5, installed in Jeeps built after March 9, 1989.


The AX15 is a split-case, top shifting, overdrive transmission with the shifter being located in the rear section of the transmission. The AX15 is fully synchronized in all gears. All gears are helically cut.

Gear ratios for the AX15 are: 3.83, 2.33, 1.44, 1.00, 0.79, for first through fifth, respectively.


The 4wd version of the AX15 transmission case is 16-1/2" long. It features a cast aluminum case with a cast-aluminum mid-plate. The case is generously ribbed and features the shifter in the rear quarter of the assembly. In the vein of newer transmissions, the AX15 uses dowel pins for bellhousing alignment.

The 4wd version of the Jeep AX15 has a 23 spline output shaft for connecting to the transfer case input shaft. This shaft protrudes about 1/2" past the rear face of the transmission.

AX15 front bearing retainer, 1994-1999

The AX15 was used with an internal slave/throwout assembly up through the 1993 model year. In 1994, a more conventional slave cylinder and cross-arm were used. The input shaft is a 10 spline x 1-1/8" and its stickout length is 7-1/2".

1989 to 1991 AX15 input shafts have a smaller (~19/32") pilot tip. 1992-1999 AX15's have a larger (~3/4") pilot tip. 1994 saw the next change with a revised input bearing retainer for the move awap from the concentric, integrated hydraulic throwout bearing to the better, external slave cylinder style bellhousing introduced that year. These later retainers (Jeep part #4636382) can be easily interchanged and are available new, here.

Differentiating From the AX5

The AX15 looks similar to the AX5 and they are occasionally confused in identification as well as interchange.

Transfer Case Compatibility

Jeep NP207

Marrying the AX15 to the NP207 transfer case as found in earlier YJ and XJ Jeeps requires that the 207's longer input gear be shortened with a hard saw or lathe to 2.1" of stickout length. This prevents bottoming of the input gear in the spline lead-outs of the AX15's mainshaft.

Adapting the AX15 to the Jeep Dana 300

Jeep NP231

The Jeep AX15 was factory-married to the Jeep New Process (aka New Venture) Model 231 transfer case.

Jeep Dana 300

Adapt the AX15 to the Jeep Dana 300 transfer case in passenger side and driver side drop by using Novak kit #153.

Jeep & IH Dana 18 & 20

Adapt the AX15 to the Jeep Dana 18 & 20 transfer cases using Novak's #152 kit.

Ford Bronco Dana 20

Join the AX15 to your Bronco Dana 20 transfer case using Novak's #1520 kit.

Adapting the AX15 to the Bronco Dana 20 transfer case

Bellhousing Adaptability

AMC / Mopar Jeep

gmax15_trans_adapter_bellAdapting the AX15 to GM Bellhousings

As the AX15 was married to the Jeep engines mentioned above, it is OEM compatible with them. It can also be adapted to 1972-1991 AMC I6 & V8 engines following this procedure.

Individuals, hoping to replace their AX5 occasionally assume the AX15 will replace it directly. The bellhousing patterns and spline counts between these similar appearing transmissions are deceivingly close, but not compatible.


The AX15 actually makes a very clean conversion to most GM engines and because it is a stronger transmission, it is well matched for the Chevy V6 and Chevy Small Block V8 andGen. III+ V8 engines. Details on these conversions can be found here. You may also find the following articles of interest:

- GM Engine Conversions in the Jeep YJ Wrangler
- GM Engine Conversions in the Jeep TJ Wrangler
- GM Engine Conversions in the Jeep XJ / MJ

A turn-key, factory new, AX15, professionally adapted (optionally) and delivered to your door - ready for a variety of engines and Jeep transfer cases. Read more...


Adapt the AX15 to Windsor Ford V8 and Ford I6 bellhousings that feature the "butterfly" Ford transmission bolt pattern using this Novak kit.

AX15 Transmission Mount

Crossmember mounting for the AX15 in factory situations means using a factory style mount. For many aftermarket and upgrade builds, Novak makes an adjustable, configurable rear mount assembly that can make difficult mounting situations easier. See them here.

Transmission Fluid

For the AX15 transmission, Synchromesh oil is our top recommendation. It's specifically designed to provide superior gear protection and smoother shifts, reducing wear and ensuring reliable performance across various conditions. Opt for Synchromesh oil to enhance your transmission's longevity and efficiency.


The AX15 is one greatest successes in Jeep transmissions. They are generally regarded as the best five-speed transmission ever installed into a Jeep. They are an excellent gearbox, and remain in production by Aisin-Warner and are available from Novak, new, in their most improved version.