OldManComanche

I tried MJCARENA's relay idea. It works great! There just wasn't enough voltage / amperage to make the hot clutch engage going through the original wiring. Thanks OHM for the tips! I was certain that there is a break or poor connection in the wiring. I looked at trying to find the splice P, and decided that when I got done there would be more torn up than what I got fixed. The relay bypasses the wiring problem and I haven't hacked up the wiring harness. I had a relay and some wiring already so it was simple.

Thank You, I will look for the splice later, it looks to be around the battery somewhere. I am going to take a little break, thermometer in my building is showing 90 degrees in the shade. I ohmed the clutch and fan hot and cold and got about the same readings, so I am not going to worry with them for now.

Ohm; I checked (5 times) the voltage at test point D2-6 and got 0 vdc both with clutch engaged and disengaged (clutch works). I see the D2-6 test point on the schematic and should be getting the voltages as you suggest. A little bit of mystery. I think I will let everything cool down and ohm the AC clutch and Aux blower motor. Run the AC till everything is nice and warn and ohm them again and see if there is a difference

The AC clutch works as it is supposed to when you first start the truck (cold), but after running for 5/10 minutes (hot) it will not energize if you shut the engine off and restart or turn AC off and back on. I think the clutch windings are OK. As I stated earlier, I can touch the clutch wire to the battery post and the clutch works as it should. I get a blue spark when I do this. When I connect the clutch wire to the wire supplying the clutch I get a VERY faint spark. Voltage at the battery, engine running is 14 voIts, at clutch wire (unplugged) about 11.5 volts. Looks like there is not enough amperage / voltage to engage the clutch. I have cleaned power distribution lugs at the starter relay, wiring connections in the circuit, cleaned the AC relay and socket, low pressure switch. I am in the process of checking wires for resistance and bad diodes. It is just GOOD Fun!

I have done a little trouble shooting and found that I also have a drop in voltage at the clutch. If I unplug the ax cooling fan then the voltage goes up and the clutch works as it should. I am now going to trouble shoot the power distribution circuit. MJCARENA, I thought of wiring past the original wiring, but I thought I would at last look at the wiring first. oldude, I also thought about the AC clutch and it's windings, clutch gets hot and quits working unless you put more voltage to it

I have the same problem. It seems to be heat related as it only seems to happen on really hot days. The AC compressor clutch won't engage. I have unplugged the wire to the compressor clutch and touched it to the positive battery post and the clutch will engage. If I keep driving the AC will start operating correctly in 5 minutes or so. Is the Thermostat Switch prone to failure or is there a more likely cause?

Do you have AC? IF SO then: The fan spins freely: are you talking about the fan that sits in front of the engine driven by the fan belt or the fan that is in front of the air cleaner? The engine fan should have some resistance when you try to spin it. The air cleaner fan should spin easily and only come on when you run the AC or engine gets hot.

There are several air gates under the dash that direct air to different air vents. Engine needs to be running to provide vacuum to dashpots to open or close them. eaglescout526 is telling you to look for vacuum leaks. LOOK FOR AC fuse blown, the fuse is 25 amps and I have seen several that weren't making good contact in the fuse box Wires not hooked up / bad connection to the low pressure switch Check the AC relay, is the relay getting power, is it working? Run 12V to the AC compressor to see if the clutch works A list of all of the parts you replaced might help.

Have you driven the truck enough to have confidence it will make the trip? Take a 2 hour drive at highway speed to sort out. Get the tires and death wobble fixed. If you haven't changed the fuel filter, do it (or at least take one with you) Take all of the tools you own with you including a good jack. If you need a tool you don't have,(while on the road) remember Harbor Freight or loaner from auto parts store. Use the interstate system to travel on so that you will have plenty of towns with auto parts stores if you need parts. I think your biggest concern is the heat you will travel through to get to the east coast. If you have heat problems, you can drive at night.

Later model AX15 transmission input shaft diameter is .750", earlier transmissions had a .590 diameter. Is your engine the original 88 I6? Measure the diameter of the hole in the crank the pilot bearing is pressed into.

Good Man! When I do stuff like this it makes me nuts till I get it back right!

I would be more worried about waiting in line and the gas gauge close to empty! My truck starts running out of gas about there.

I don't think it does anything other than act as a bumper for the slack side of the timing chain, it isn't spring loaded to keep tension on the chain. I would guess that it keeps the chain from slapping around (noise) or engine turns backwards accidentally. Having said that, If it was me, I would pull the cover off and put it in. My theory is "if it wasn't needed, Jeep wouldn't have put it in! I get to thinking about stuff like this that I have done and it makes me crazy!! (make a note for ME so I will remember what told you next time!)

I thought I was the only one who can't remember what I did!! Why did you have the cover off? replacing timing chain?? Most of the chain kits I have seen will have a replacement rubber cushion.

coolwind57, You mentioned a "knock" sound in the original post, a loose timing chain will knock or rattle especially at idle speed. From the pictures, you NEED a balancer, but from the description you may need a new timing chain / sprockets. The kits usually have chain, sprockets, cover gasket, chain cushion, and a crank seal. The timing chains that I have done had an amazing amount of slack in them. The Jeeps ran noticeably better after replacing the chain.

Is the old bumper still installed inside the cover? Do you remember how worn it was?

You got it! I did this a couple of weeks ago. No major problems. The three holes around the center bolt are threaded, so you can screw bolts into them when you use a puller. Pull the center bolt and give it a squirt of penetrating oil and let it sit for a while. When you get the balancer off check the cam chain cover for a wear groove due to the rubber cushion bulging out. Also if you need to change the timing chain (loose, slack) now is your chance as you have already done the hard part. Have fun!

That was kinda my thoughts too. A little research on the worn pilot bushing shows it originally had a bore of .625" to .630"(5/8) the good used input shaft I have (small pilot, no wear) measures .590" at the pilot bearing end. So that leaves a clearance of .035 to .040 inch. The input shaft could wiggle around until it wore the pilot bushing out. This is a chicken or egg kind of a thing. It started out as something wasn't quite right and turned into a bunch of things were really wrong.

There was so much this deal that didn't make sense. I bought the Jeep not running. I got it to run (a story in itself). The clutch / transmission made a BUNCH of noise and vibration but would move the Jeep around. Transmission appeared to be correctly installed to the engine. Pulled the trans and found the pressure plate hub loose, Input shaft would make an orbit about 1.5 inches around. Inside the transmission was pretty bad also. The only thing I saw from the wear in the bearing was that the input shaft only stuck into the pilot bearing about 3/8th inch -- bearing driven too far into the crank?? I rebuilt everything and it all works great. I don't know if sand got into the pilot bearing and it eventually egged the bearing bore or what?? It now runs very well and shifts great. I stopped worrying about it and just drive it. On To The Next Problem!

This is the pilot bushing I removed from a 90 Wrangler (same setup as OP has, 97 4.0 & small pilot AX15). The bushing hole was so egg shape, as I said, you could stick your thumb in it. Everything south of the pilot bushing was junk because the input shaft was flopping around and chewed up the transmission. I spent about $1000 on clutch, shafts, bearings, syncros, gears, etc. I replaced the small diameter input shaft with the later large diameter stuff. I did all of the mechanic work myself (I work for free). I still haven't figured what went wrong to cause this, except the bearing failing. Thoughts?? The Wrangler had 7" lift and 35 inch tires. With the mud, rocks and sand we have around here, I am sure the engine/clutch could get pretty hot, this may be a factor. Or sitting in 4' feet of water? I think the needle bearing is better, and the large pilot needle bearing is better still. I agree with BeatCJ, everything I have heard about Novak's parts is good. In this world there are people that can tear up a bowling ball with their bare hands!

My bad experience with a brass/bronze bushing makes me favor a needle bearing (like OEM). The guy that I bought the Jeep from told me that he had " a shop" do the late 4.0 to early AX15 swap. I believe that I would rather walk as to use that "shop". My guess is he was the "shop". Back in my early years of auto repair, all, of the cars used the brass bushing and I never had problems with them. But I made sure they had a little grease on them when I put the trans in.

If you could use the expansion arbor on the needle bearing and do as you suggest, just reduce the OD it would be just about like factory. I am not familiar enough with the expansion arbor to know how that might work. The needle bearing might allow the outer diameter to free wheel and no material would be removed.(I'm not sure) If it would work, the bearing the OP tried to use could then be made to work. I like it! Take what you have and make it work!

Do you have a machine shop, friend etc. that can machine the OD of the bearing you have down to the dimension you need for the later engine?

I thought the "small pilot bearing shaft" was closer to 5/8th inch (.590") The Jeep I was working on (YJ) had a custom made bushing that had the pilot shaft hole egg shaped. I don't know if it was poor workmanship, soft brass, or just plane poor setup. It was worn so bad that you could put your thumb through the hole. It ruined the end of the input shaft, clutch, gears, bearing, syncro, and sliding hub. I went the way I did because I was already going to have to change the input shaft, so why not go to the later style, larger bearing input shaft. I AM SURE THERE IS A SORCE FOR A PILOT BEARING THAT WILL FIT LATE CRANKSHAFT TO EARLY PILOT SHAFT. If you are in a jam, do like Pete M says and have someone locally make you a bushing. I found the complete disassemble and reassemble procedure at SCRIBD.com,.. look for Jeep AX 15 service Manual Transmission. They let me look for free and then blurred the images and wanted money later. Instructions and images were excellent. Daddy used to say: If you half a** something, you get half a** results! And if you half a** it again all you have is one whole a**!! It took me a long time to learn this.

Rebuilding the transmission with the late style 3/4" input shaft/pilot bearing IS EXACTLY WHAT I DID when I was in this exact situation.(97 motor / 89 AX15). You can use the correct pilot bearing for the later motor with the AX15 3/4" input shaft. AND you have a better transmission input setup, there is a reason they went to larger shaft and bearing. Remember you will have to tear the trans completely down to put the input shaft in, I isn't just unbolt the snout off of the transmission and change shafts!! If you decide to go this way let me know and I can point you to good trans rebuild instructions!