AX5 to AX15 transmission swap

It happens to us all. You buy a Jeep, off-road it, get stuck, upgrade it, it’s a never-ending cycle. In this article, we will go over an AX5 Transsmion to AX15 transmission swap along with a Dana 300 in a 1991 Jeep YJ 2.5L without breaking the bank.

Our AX15 Transmission Adventure

AX15 Transmission Swap -  Taking it for a test drive!
Sometimes you have to show your Jeep who’s really in charge.

The reasons for going with an AX15 transmission and a Dana 300 is the strength, reliably running a larger 32″ tire, but most importantly, the front axle in our YJ is a passenger-side drop Dana 44.
You might ask why we went with a passenger-side drop instead of a Ford high pinion 44?

Well, the front and rear axles we scored for free from a rusted out CJ-5 that was about to be hauled to the crusher, so why not toss them into our bone stock YJ! We’ll talk about the axle swap in the next issue, let’s get back to the transmission swap!

AX15 Transmission Swap

For this swap, taking out the transmission is relatively straightforward. You can follow your manual for this one. Don’t forget to unbolt the crank sensor from the bell-housing before removal!

We were able to remove the transmission, transfer case, and rear driveshaft as an assembly. Notice the oil on the bell housing from a leaking valve cover gasket. With the transmission removed, we can start to science out installing our replacement transmission. In case you didn’t know, the AX5 and the AX15 transmission use completely different bell-housings. The pattern on the front and back is different, so you cant swap one bell-housing to another transmission and back.
You can buy adapter kits to swap them around, but we opted for something a little cheaper.

Using www.car-part.com, we searched for AX15 transmissions and bell-housings from 1996-2000 Dodge Dakota pickup trucks. These trucks use a 2.5L engine, same as our YJ, but use an AX15 transmission for added strength. They only come in 2 wheel drive, so the transmission was no use to us, so we bought just the bell housing. We were able to have one shipped to us for a $100 bill, not too bad.

The donor transmission came from a 94 Jeep Cherokee. The only difference between a YJ and an XJ AX15 transmission, is the transfer case holes are clocked a few degrees differently, this didn’t matter to us because we have to use an adapter ring to mount the Dana 300 to our AX15 transmission, more on that later.

We scored the transmission from a local (100 miles away) pick-n-pull on a 50% off weekend for right about $100 bucks out the door, now that’s a good deal on an AX15 transmission, good enough we decided to toss a rebuild kit in it.

We will outline the rebuild in an upcoming issue!

AX15 Transmission Swap

The bell-housing went onto our AX-15 transmission without any modifications. After our bell-housing was installed on the AX15 transmission, we found the input shaft to be shorter than the AX5 shaft.

Luckily for us, this swap has been popular enough that advance adapters already made a very stout bushing to address this problem. With part #716167 from A.A. installed in our flywheel, we were almost ready to install our new transmission.

This is where things get a little unusual. It turns out the AX5 and 15 both have very different mounting brackets to mount to the cross member. We wanted the shifter to poke up through the original hole and not have to modify anything on the inside of the jeep, so we wanted to avoid fabricating something for it.

The bell-housing went onto our AX-15 transmission without any modifications. After our bell-housing was installed on the AX15 transmisson, we found the input shaft to be shorter than the AX5 shaft.

Luckily for us, this swap has been popular enough that advance adapters already made a very stout bushing to address this problem. With part #716167 from A.A. installed in our flywheel, we were almost ready to install our new transmission.

This is where things get a little unusual. It turns out the AX5 transmission and AX15 transmission both have very different mounting brackets to mount to the cross member. We wanted the shifter to poke up through the original hole and not have to modify anything on the inside of the jeep, so we wanted to avoid fabricating something for it.

Looking at the following diagram, you can see the AX5 transmission mounting on the left and the AX15 transmission mounting on the right.

AX15 Transmission Swap Chart

We needed part #4 to install our transmission and have it be in the correct location both forward and back, and up and down.

It turns out this bracket has a part # of 52003925 and is only for the YJ initially with an AX15 transmission. Of course, with our luck, this bracket was discontinued. Our trusty website of car-part.com was at the rescue again.

After searching and making several phone calls to wrecking yards with 1991-1995 YJ’s sitting around. We finally bagged a bracket for a 75 dollar bill.

AX15 Transmission Swap

We have our transmission all ready for install with all the previously mentioned parts. By far the easiest part of this project was adapting the Dana 300 to the AX15 transmission.

AX15 Transmission Swap transmission adapater

The adapter came from eBay from a company called 4wheelsupply. The kit is a 7/8″ thick tool steel ring with a set of countersunk Allen bolts and a set of studs and nuts. You use the bolts to bolt the ring to the Dana 300. After that, the Dana 300 can be installed onto the back of the AX15 and “clocked” to any position you desire. Now you thread in your studs until they bottom out, and finish them off with your nuts. Remember when we said the XJ transmission in the YJ would not be a problem for us?

Most people that do this swap we have found use a clutch disc from a Camaro with a gm 2.5 engine. At the time, we weren’t able to get a parts house to sell us just a friction disc as we wanted to reuse our recently replaced pressure plate. After lots of internet surfing, we found a clutch disc with part # J8132577 from crown automotive. This is for an early 80’s CJ with the GM 2.5 engine and happens to be about the correct overall diameter and the correct spline size, plus it was available by itself and shipped to us for free.

With the clutch assembled, and the transmission assembled we did find we had to trim the transmission rubber mount just a hair on the corner to fit the Dana 300, not a big deal, we installed the assembly into place. Once the transmission had been bolted to the back of the engine. To our surprise, we couldn’t install the cross member/belly pan assembly. The transmission sat about 1 inch too far back.

AX15 Transmission Swap
AX15 Transmission Swap

Considering the jeep would be getting an engine swap in the future, and we wanted the transmission to be located in the original location as if it had left the factory with an AX15 transmission, we decided to jack up the engine and pull the motor mounts loose. Then we slid the entire assembly forward until the mount fell into the factory holes in the skid plate. On the passenger side of the engine, we found the little spacer plate broken into three pieces. You can see the original next to the one we built a shackle and a bolt we had laying around to move the engine forward.

The driver side motor mount took a little more engineering. On this side of the engine, there was no spacer plate from the factory. So we cut the frame mount down the middle and slid the ear forward to the correct position and welded it back together along with a piece of the strap for support all through the cross-section of the mount. The other hole for the mount just required us to drill and tap a new hole. We then set the motor down on the relocated mounts. Once lowered down and bolted together, to the naked eye you can’t even tell we moved the engine forward. 

You can see in this picture we topped off our transmission with a B&M short-throw shifter. The XJ shifter is the incorrect shape for the YJ (pretty short), and the shifters cannot be swapped from AX5 transmission to AX15 transmission, so we jumped on the summit and ordered our short-throw shifter. Also, notice house the shifter housing is perfectly aligned in the factory hole. No cutting or shifter getting caught on anything.

During our final steps of installation. We decided to twin stick the Dana 300 and fabricate linkage that would stab through the original hole in the floor (at this point, why not). This was when we realized the transfer case was rotated too far up and we didn’t have any room to run any linkage over the top of the bellcrank in the bearing retainer.

We ended up clocking the 300 down one more set of holes, which in turn made it, so we had to trim some of the transmission cross member/belly pan assemblies. However, the transfer case still sits up inside the pan; we did not want to sacrifice ground clearance at all. Once we did that, we had to cut one ear off the bellcrank and proceeded to fabricate the linkage necessary to build our twin sticks. We used some metal strap to build ears off of the shift rods. Then from there, we used a pair of heavy duty ball studs welded to more strap material, which then got welded to a solid rod which made its way up and over the transmission and through the hole in the floor.

AX15 Transmission

We modified the factory shift boot with the twin stick boot again from eBay. Although not pictured, we ended up topping all three levers with factory style shift knobs which makes the assembly look very sharp if you’re going for a stock look. We ended the project with custom driveshafts. We were able to re-use the factory front driveshaft. However, we had to shorten it a few inches to make it the proper length.

We made the front driveshaft on the workbench in the house, however for the rear we wanted to be 100% sure to have a top quality product. We gave Tom Woods driveshaft a call. Within about 10 minutes we had a custom one-off driveshaft complete with u-joints ordered up and headed our way. Once unpackaged we were extremely impressed with the quality, it fit and worked perfectly. If your local shop has quite a backlog, we strongly recommend Tom Woods. They have a top quality product at a great price.

Have any questions regarding this swap? Let us know. Check back in our next issue for more work on the 1/2 Ton YJ.

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