The Following Post Details the DIY Conversion of a Jeep Cherokee From Automatic (Aw4) to Manual (AX15) Transmissions. Mechanical Work And Drivetrain Conversions Should Be Attempted Only By Those With Proper Training/Experience. Drivetrain Modifications May Cause A Vehicle to Handle Differently, Affect Emissions Testing, Etc. Craftsman Collaborative Accepts No Liability For Any Issues/Damages Surrounding Tech Write-Ups. Wrench at your own risk.
Introduction & Tech Write-Up:
The elusive AX15 Swap. Some say it’s a quick conversion. Others – that you’re better off to buy a new Jeep with the transmission you want. Our experience converting a 2000 XJ from auto to manual split right down the middle – It’s doable with the right methods, parts and time in the garage.
Choosing a Manual Transmission:
Why The AX15?
There are multiple transmissions out there that could be dropped into the Cherokee XJ – A few OEM options and countless swap possibilities from other vehicles/platforms. That said, most folks will opt for the proven AX15 swap – and for good reason.
Non-OEM transmissions can require extensive conversion kits to match up the engine, bell-housing, transfer case, etc. These tend to fetch a pretty penny and longer parts list than the AX15.
For those reasons alone, sticking with an OEM solution will make for a more-or-less guaranteed fit. The AX15 is the most direct swap, while other OEM XJ transmissions have a rough history of unreliability – read more here.
Less time in the garage and more time on the trail – never a bad tradeoff.
AX15 Variations & Factory Options:
There are a few variations when it comes to the AX15 manual transmission platform. Although offered in multiple different Jeep models through the year, it is best practice to source an AX15 directly from an XJ Cherokee.
A successful automatic to manual transmission swap will require more than the transmission itself – so having a full donor vehicle to source matching factory transfer case, driveshafts, pedals, etc makes quick work of a parts list.
Converting 2WD Jeep Transmission To 4WD
Working on a 4×4 vehicle? You’ll need a 4×4 specific transmission. Steer clear of any 2wd donor vehicle, as this transmission is not compatible with 4×4. The output shaft on the 2wd AX15 goes direct to the driveshaft, while the 4×4 transmission has an output shaft that mates up to the transfer case. The 2WD AX15 cannot be converted to 4WD – they are two separate builds.
Which Year AX15 Is Best?
Through the production-life of the AX15, few major changes took place.
The most notable comes in the shift from an internal slave cylinder (1989-1993) to a more conventional external slave cylinder (1994-1999). We went with the 1994+ style AX15 as the external slave cylinder is much easier to service. The slave cylinder can be serviced or replaced without having to tear into the transmission/bellhousing, the key issue with the pre-1994 AX15.
Which Transfer Cases Work With The AX15?
The next big question when converting a 4wd transmission is which transfer case should be used. The AX15 came factory-mated to the NP231 transfer case, and is the go-to OEM option for Jeep Cherokee XJ’s and many other Jeep vehicles.
There is a bit of Jeep forum talk out there on swapping in an NP242, the other common factory option on Jeep Cherokees, but in our experience sticking with a matching manual-transmission NP231 brings peace of mind and reliability on the trail.
What Is The Difference In Manual vs. Automatic Transfer Cases?
There is a notable difference in the length of input shafts from manual to automatic transmission. The AX15 typically is paired with a 23-spline short input NP231, while the post-1990 AW4 (XJ automatic transmission) is paired with a 23-spline medium input 231.
It is easiest to source a matching transfer case with the donor manual transmission and save the headache of verifying input length matches. Any time a model-year or transmission mismatch is present, it is crucial to ensure both the spline count and shaft length of the transmission and transfer case align.
Key Takeaway: The Golden Donor
Based on the specs and options outlined above, the ideal donor for our Jeep Cherokee Manual Swap was a 1994-1999 Jeep Cherokee XJ with a factory AX15 manual transmission and 4WD. The donor should have an NP231 transfer case that matches up with the manual transmission.
This would give us the robust build of the AX15, with the easy-to-service external slave cylinder. Sourcing a vehicle with a matching transfer case means one less headache in matching up parts, and seeing that the full assembly comes from an XJ Cherokee, it should be a direct swap for our build.
Sourcing A Donor: Jeep Cherokee Manual Swap
There’s a few options when it comes to sourcing a donor. Purchasing an entire donor vehicle is one route, with an often higher cost up front but the potential to recoup costs on selling off other components. The next most accessible route is to pull the parts from a pick-and-pull junkyard. Finally, it may be possible to source out the parts individually online or from other suppliers, but this often comes with a much higher price tag.
On the 2000 Cherokee Camper Build, we held out for just the right junkyard donor. After a year or so of casually looking, we came across the perfect option: a 1998 Jeep Cherokee with all the works. An AX15 transmission, NP231 Transfer Case, and a complete assembly of all other conversion parts to check off our list. One goldmine of an XJ – we set off for the junkyard with a packed toolbag and went to work before bringing it home to the 2000 Cherokee Build.
Common Issues With The AX15:
Top Things To Check For & Avoid
When sourcing a used AX15 transmission there’s a few key things to look out for. Firstly, check the casing ID to verify it is in fact an AX15 and not the lesser-supported AX5. Next, inspect the transmission case and bell-housing for any cracks/damage or otherwise. With the transmission removed from the vehicle, cycle through each gear while turning the input shaft by hand to verify all gears engage and spin freely.
While sourcing our AX15 from a donor 1998 Jeep Cherokee, we were able to pass each of the above tests and felt comfortable in pulling this transmission for our Manual XJ Swap. As a 20-year old transmission, we still had plans for a full rebuild but these tests saved us the unforeseen costs of replacement gears and drive parts. Details – Sourcing & Rebuilding AX15:
Full Parts List:
What’s Required For Jeep Cherokee AX15 Swap?
Beyond sourcing a transmission (above) the complete conversion of a Jeep XJ from an automatic to manual transmission requires an involved parts list. Differences in everything from transfer case and driveshaft lengths to pedal assemblies and steering columns add up quickly. Get the right parts the first go around – and the swap will go much, much smoother.
Full AX15 Swap Parts List:
Sourced From Manual Transmission Donor Cherokee:
Jeep XJ Manual Transmission: AX15 (Pref. 1994-1999)
(Complete with transmission, bellhousing, shifter assembly, etc)
Jeep XJ 4×4 Transfer Case (Matching NP231/Manual Spec)
Manual Trans Front Driveshaft (Length Is different Than Automatic)
Rear Driveshaft (Rec. Aftermarket Upgrade To Double Cardan DriveShaft)
Manual Donor Crossmember & Transmission Mount
Pedal Assembly W/ Clutch Pedal (Clutch/Brake Combined Assembly)
Clutch Assembly, Master & Slave Cylinder
Throwout Bearing & Shift Fork Assembly
Flywheel, Flywheel Hardware, Flywheel Cover, Etc.
Steering Column (May be able to modify Auto column to work – see below)
Interior Shift Boot/Trim Fitting
Manual Transmission PCM/ECU (Needs to Match Your Vehicle’s Year & Reflash, See Below)
Replacement/Service Parts:
Transmission Mount, AX15 Rebuild Kit, Proper Pilot Bearing, NP231 Rebuild Kit, Clutch Kit, Master & Slave Cylinder Kit, Ax15 Oil (10W-30), NP231 Transfer Case Fluid (ATF+4), Gaskets & Tube of Gasket Maker. Replacement shift boot, shift knob, etc.
Aftermarket/Upgrade Parts:
Rear Driveshaft – Double Cardan Upgrade
Slip Yoke Eliminator Install (Recommend for all lifted / 4×4 builds)
AX15 Swap – Install
With the parts list above, the transmission install itself follows a few straight forward steps. Pull the old AW4 assembly down to the engine and install the AX15 rebuild complete with clutch assembly & matching pilot bearing.
A factory service manual makes easy work of assembly and torque specs here. As the AX15 is a factory swap on the XJ, with the right parts install should be straight forward, including pedal assemblies, clutch kit, etc.
PCM Install & Check Engine Light
Swapping an auto to manual Jeep without a re-flashed PCM presents a few key issues: the PCM/TCM will throw check engine codes for the torque converter and shift solenoids, as well as cause a no-start issue from the neutral safety switch. There’s some info on wiring workarounds on Jeep forums, but if the vehicle build allows, an OEM flashed PCM is the call.
Transmission Control Module Bypass
With a proper OEM manual reflash, the Cherokee’s TCM should be bypassed, at least in model years like our 2000 XJ that have a separate Transmission Control Module (TCM) and Engine Control Unit (ECU).
On a 2000 Jeep Cherokee, the TCM is a small box mounted underneath the dashboard, above the driver side transmission tunnel. In our build, we were able to remove the TCM without issue, as the manual PCM won’t receive any feedback from the circuit upon re-flashing computer modules.
Wiring Harness Modification
With a matching year PCM re-flashed to the manual transmission software, there will still be a few issues in using the original automatic transmission wiring harness. While the re-flash tune will disable torque converter solenoid and shift solenoid feedback, we ran into a no-start ground issue along the NSS circuit.
Using a factory wiring diagram we narrowed down and grounded the necessary wires on the auto harness to make everything work just as it should. After studying both the auto and manual transmission PCM wiring diagrams we figured a workaround in grounding the respective wire that the manual PCM required to start.
Steering Column Modification
The automatic Jeep XJ steering column comes equipped with a park interlock cable – stretching from the steering column to the back side of the auto shift handle. On our build, simply removing the cable from the column allowed the Jeep to function without issue and kept the key from sticking.
Reverse Light Circuit
The AX15 comes equipped with a built-in reverse light switch, and will need wired up to the automatic wiring harness, or alternatively used as a switch in an auxiliary reverse light circuit. We opted for the second option in our build, wiring around the switch to control an LED reverse light solenoid.
More AX15 Swap Details:
While the parts list above can give a straight forward idea of what will be needed to pull off an AX15 swap, there are always those little details that can present themselves in the middle of install.
Spend a little extra time studying other’s builds on Jeep forums to get an even better idea of the swap process. We’ve found the below youtube series to be a goldmine. Wish this was around when we went to work on ours!
**Not Affiliated with Craftsman Collaborative**
Install Takeaways:
The greatest part of the AX15 install follows having the right parts and a reliable/rebuilt donor transmission. Not to mention the tools and know-how that go with any driveline project. As an OEM swap, the transmission itself should bolt up without a great amount of work – the tricky part comes with pulling off a clean install.
Removing obsolete parts from the AW4 – including shift cables, wire harnesses/connectors, etc makes the difference between a hacked install and one that appears as it came from the factory.
The electrical aspect of the swap varies from year to year – and the only tried & true method to get it right is to understand the fundamentals outlined above, and study up with a factory service manual wiring diagram. Without a reflashed PCM, this will be a tricky install – no way around it.
With a reflashed PCM that runs manual transmission software, the most common issues come with missing ground circuits. An entire wire harness could be swapped over to work around this. In our case, we reused the automatic harness with a few splices and changes – all routed and fused accordingly.
AX15 Swap Outcome:
Through a complete DIY AX15 rebuild, install, and detailed conversion, the 2000 Jeep Cherokee build now looks and drives as if it came equipped with a manual transmission from the factory. Even the dashboard shift light illuminates at higher RPM’s – thanks to the factory reflash.
Can’t beat that for a clean install!
No check engine lights, no rough shifting, and no loose ends.
Done and Done!
Related Content:
AX15 Swap – Jeep XJ Complete Conversion Guide
Jeep AX15 Transmission: Complete Rebuild Photos