Hi, this is my first post to a Jeep Forum. I just wanted to relay some details about my 1994 YJ project. Last summer (2012) I found a 1994 YJ 2.5L 5spd for $2,500. Even though it had 230,000 miles, I couldn't pass it up! The transmission was noisy and wouldn't go into 5th, so I knew about this up front. I rattled around with it all summer, including a trip to the dunes in Florence, Oregon where we hammered it all day long and it never let me down! I think the engine is pretty solid, but had to do something about the transmission. (I'll try to post some pics later).
Enter the internet, I found an article in the forum about swapping to the AX15. I also found articles about what was wrong with my AX5 and how to fix it. Then I found an AX15 used on craigslist for $100, and ultimately bought it for $75. This kind of made my decision for me, and I was "off to the races"! The previous owner told me it was from a 1994 Wrangler, and that it worked fine although reverse had a "tick", and that the person he bought it from said he had driven it for 3 years that way!
To do this swap, according to the article I read, you needed a special pilot bushing, a clutch disk from a 1994 Camaro 2.5L 4spd, a 1994-1996 Dodge Dakota bellhousing from the 2.5L, 5spd 2wd truck and also, a 23 spline input shaft for the transfer case.
I gathered parts...the bellhousing came from a local wrecking yard for $125, the clutch disc from eBay for about $35, the pilot bushing is available online for about $20. I realized that I would need an alignment tool, so I bought a wooden dowel type alignment tool for a couple bucks. Be careful buying the input shaft, apparently there are several different lengths for this item, and I bought two used ones before getting the right one. I could have bought new, but this is a budget project, so some things were overlooked that could have been done. If I had lots of money, I would have rebuilt the transmission, put a new rear main seal in the engine, replaced the clutch pressure plate and throw out bearing, etc, etc. But this stuff all seemed useable anyway. The transfer case was immaculate inside, good bearings, seals, minimal chain stretch, so I didn't replace anything here either, except the input shaft and the planetary, because I bought them together. The guy would not separate, and I thought it might be better to run these two together, as they were broken in that way....but I'm getting ahead of myself.
Don't have a garage at the moment, so I did this in my backyard, under a canopy my brother in law loaned me. I estimated two weeks, but it turned into a couple of months of weekend work. My mechanical skills are not that good, but I find it interesting, and I have a lot of patience. My wife kept asking me if I was done yet. The stock answer was always "give me another 5 minutes..."
I don't have a transmission jack, so I took things apart before dropping them out. In other words, skid plate first, lowered things with my floor jack and my son helping, driveshafts, then took out the transfer case, then the bellhousing/transmission.
I was able to do this swap with the exhaust pipe in place, although I did loosen the bolts where it connected to the manifold. I used two long, threaded studs to draw the replacement Dakota bellhousing/AX15 up to the engine, as I wasn't able to just shove it into place.
Here are some things I found out while in the midst of it:
1.) The stock transfer case shifter will not fit, so I bought a used one for the AX15 from eBay. Yes, the transfer case shifter bolts to the transmission.
2.) Using my stock shifter, the center console was in the way for hitting 2nd, 4th and reverse, so for the moment, it has been taken out.
3.) The front driveshaft still bolts up, but there is NO TRAVEL, because, duh, it has to reach 2 inches farther back.
4.) The shortened rear driveshaft I bought online has a smaller U-Joint than my original. I will have to take both driveshafts, and have them modified/rebalanced at a local driveline service shop. This will cost about $86 each.
5.) I had to modify the skid plate to accomodate the new transmission and mounting bracket, by cutting about 6 inches out of the middle cross member. I don't have access to a welder, but plan to weld in some angle iron to compensate for the lost strength due to the cut. I had to drill 4 holes in the skid plate to bolt the mount on. I made a template for this. To figure out where to drill, and with the transmission in place, I put the front two skid plate bolts back in the frame, strung a line between them, and then measured from the middle of the string to one of the transmission mounting bolts.
6.) The transfer case, to install the input shaft, has to be COMPLETELY disassembled, as that component is about the last thing you come to after splitting the case. This looks like a daunting task, and I put it off as long as possible. You can find youtube videos about how to do this. I must say, it wasn't that bad. The hardest part was getting the front yoke off, as it is bolted on at about 110 ft. pounds. It took two of us with wrenches and cheater bars. An impact wrench would have been very handy here. All I needed for this was the RTV sealant to reassemble.
7.) I don't yet have a solution for the middle exhaust pipe support, but will maybe cut that off and install an exhaust hanger somehow.
Finding the transmission mount turned out to be the most difficult as I was ordering for a 1994. What ultimately fit though, was a 1997 transmission mount! The transmission/bellhousing assembly ends up being just under 2 inches longer than stock.
Coming down the home stretch, at the rear driveshaft, I took two of the caps off the old u joint and put them on the replacement u joint in order to get rolling. This is a TEMPORARY solution, and as I said, I plan to take both driveshafts and have them rebuilt soon.
Bleeding the slave cylinder was the last task. To be fair, when I took this apart, someone had put electrical tape around the rubber thingy that the plunger goes through. But it had been working, right? Although I had a slow leak, I freshened it up with new electrical tape. Bad idea! I tried driving it, and we got around, but didn't have much clutch pedal. So it was difficult to shift. As we drove it more, it seemed to be getting worse, so I tried bleeding the system. This was difficult to find out how to do, as there is no bleed screw. (youtubed it) I ended up reaching past the flywheel (rock shield removed) with a wrench, and then pushing on the lever that holds the throwout bearing. This in turn pushes on the slave cylilnder's plunger, causing the air bubbles (cap removed from the m.c.) to percolate up through the master cylinder. We had the system pretty well bled and ready to button up after about 5 minutes, when suddenly it puked out all the fluid. Guess my electrical tape fix didn't hold!
I ordered a new slave cylinder, then the next day, it dawns on me that I should have ordered this part for a Dakota, not a Jeep because of the bellhousing. Sure enough, they are different part numbers. So I ordered both from the auto parts store with the understanding that I will return one. I want to compare how much throw is in the plungers, and if the connections to the hydraulic line are the same...hopefully that stuff will be here in a couple of days. I'll post how that turns out.
Things not to worry about
1.) The old crankshaft position sensor seems to be happy and works fine in the Dakota bellhousing. This thing runs like the proverbial swiss watch. I don't know how many miles are on the engine or its history, I assume it isn't the same as the vehicle mileage, but it doesn't seem to use much oil.
2.) Transmission electrical connections matched up. I believe this is for the upshift indicator light, but haven't researched it. The indicator still works, so...there you go.
3.) Hang in there and you'll get your project done! Talk to folks, do internet research. If I can do a project like this, you can too!