Adapting the

AMC 2.5L (150cid) Engine


GM Transmissions

This guide will show you how to replace your light-duty AX5 as found behind the AMC 2.5L I4 engine with something completely substantial, like the SM420 or SM465 transmissions. This is a more advanced swap, but the thoughtful installer will be able to do excellently reliable work.

Product & Features

Applications & Compatibility

The Novak Kit 

* This kit is currently deprecated and not available for sale *

Novak can provide the following specialty parts to assist in completion of this conversion: 

  • Bracket, mounting, crank position sensor
  • Pivot ball, specially modified for adjustable height
  • Adjustable pivot bolt, 10mm & lock nut


The kit includes the specially machined pivot ball, crank position sensor (CPS) bracket with hardware, and pilot bushing.

Parts Required


The installer will need to source the following parts. These are suggestions only and do not constitute a guarantee of fitness or applicability:

  • Bellhousing, Chevy S10 Blazer. GM #15679692. This is the bellhousing that was used with the 2.8L, 60 degree V6 engine from 1985-1989. GM no longer manufactures this bellhousing, but salvage sources are an option
  • Plate, cover, bellhousing lower, GM #15602627
  • Pressure plate, & Disc, 9-1/8" diameter x 10, 1-1/8" splines available below
  • Bearing, throwout, BCA #614037 is one possibility, but the best option is to use Novak's adjustable release bearing, #TB1 available below
  • Arm, clutch release, GM #15704443
  • Cylinder, hydraulic slave clutch release. Try #SC103471 or Centric #13862003
  • Starter motor, gear drive style. Consider the Mean Green #3212
  • Adapter, hydraulic clutch release line (below)

CPS Provision

You may use your existing CPS (Crank Position Sensor). You will need to drill or otherwise machine your bellhousing to accept this sensor. The Novak CPS bracket and your CPS will offer you a good template for doing this modification.

sm420_to_150_3Suggested Transmissions 

The ultra-low geared SM420 or SM465 transmissions will add fantastic off-road and crawling abilities to your Jeep powertrain. These are the most often requested transmissions and will offer the best overall performance.

The SM465 is more difficult to install in that it requires that the bellhousing bore be machined to precisely accommodate the 5-1/8" retainer locator. Also, use of the suggested slave cylinder will require that one rib be machined off the SM465 on the driver's side. As such, the SM420 is usually an easier choice for installation.

We recommend that you run a 33 inch or greater tire or change your axle gearing to compensate for the loss of your overdrive gear. See our gearing page for more about this.

Transfer Case Shifter

This transmission conversion will work best with our #SK2X transfer case shifter kit. Factory shifters could be modified, but this usually results in a bigger mess than even the factory created with their shifter system. Available below.

Transmission Shifter


Use of the OEM style transmission shifter for the transmission is easily done. The installer may opt to bend the stick to fit the particular Jeep application. The transmission shifter sits further ahead in the Jeep than the AX5 and will need to be modified accordingly.


Note that you will be able to shorten your drivetrain length and lengthen your YJ or TJ rear driveshaft for better angularity and less strain and vibration. The front driveshaft will be lengthened a corresponding amount.

Engines & Engine Mounting

Your engine will remain in its factory location.

Related Products

Clutch pressure plate and disc 2.5L engine to 10 spline 1-1/8”

Optional Adapters for Later Model Jeeps 

These useful adapter fittings permit the adaptation of 1991-present Jeep master cylinders that use O-ring style fittings -- our #HCR8 line and other standard fittings. These adapters feature a male 1/4" (tube size) DOT threaded end so that the installer can use standard hydraulic lines and hoses for the particular situation. The tip inserts into your 1991-1995 Jeep YJ (and 1991-1996 Jeep XJ) or 1997-present Jeep TJ & XJ master cylinder using the factory style O-ring and retaining pin. We recommend that you verify your particular fitting with the image and descriptions below prior to ordering.

Note that 1980-1986 CJ's and 1987-1990 YJ's master & slave cylinders already feature a female DOT fitting and do not require these adapter fittings.



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.


Transfer Case Shifter

Often the shifters are linked to your old transmission, body, or both. As things move or even just to have a better setup these shifter solutions prove invaluable and extremely popular.


Installation Requirements

Installation will be as described above and in any instructions accompanying the individual kits.

Also See