Hiroler Posted December 4, 2014 Share Posted December 4, 2014 Hi guys. This noise occurs when I start up the comanche or let off the gas. It seems more prevalent in park or while turning. It sounds like a squeaky fan and like its coming from the transmission area. It was occasional for a year but it's been regular lately. Sometimes the engine has a crunchy noise when starting too. Other times there's no noises at all. Moody. Daily driven, 308k miles, drives great and engine runs awesome. Recently replaced fan clutch but doubt that's the culprit. Edit: a/c compressor disconnected and heat controls have no effect. Thanks for your help. I just thought maybe someone was familiar with this sound. Google led me to possible a torque converter bolt? Kyle Link to comment Share on other sites More sharing options...
gogmorgo Posted December 4, 2014 Share Posted December 4, 2014 Auto tranny? It does sound pretty similar to the noise my MJ was making under similar conditions (i.e. at idle or when not under acceleration or deceleration loading), although mine was more of a clatter than a squeak, but it did occasionally make crunchy or grinding sounds. Turned out to be a cracked flexplate. If you can get ahold of a mechanic's stethoscope (~$5 at harbor freight) it could make finding the sound easier, although my flexplate never showed up with the stethoscope. For sure check the flexplate/tc bolts and inspect the flexplate itself. There are a bunch of write ups for it online, but it's just crawling underneath, unbolting the inspection cover (thin sheet metal on the lower portion of the bellhousing), and turning the engine over by hand (3/4" socket on the crank pulley bolt, only turn clockwise) until you've seen all four bolts. Check the flexplate for cracks, in particular around where it bolts to the crank. A bright light will help, as you might catch a reflection off the slightly raised edge of a hairline crack. That's honestly all I saw, and I wasn't even certain my flexplate was cracked until I pulled the tranny to change it... the crankshaft flange was hiding the crack which went all the way around the bolt circle and separated the plate into two pieces that were magically still somehow transmitting torque. Use a socket on the flexplate bolts to make sure they're tight, IIRC it's a 15mm. For what it's worth, my cracked flexplate came with all kinds of other intermittent running problems. Since the crank position sensor determines ignition timing by reading off the outer edge of the flexplate, and my flexplate had about 10 to 15° of rotational play between the inner and outer pieces (note it was broken, there's usually only one piece) and almost twice as much perpendicular to the rotation, my cps was having a hell of a time doing anything useful. The cracked flexplate lead to a bunch of no-starts and occasional stalling while underway. Link to comment Share on other sites More sharing options...
Hiroler Posted December 4, 2014 Author Share Posted December 4, 2014 Yes auto. Thanks for the reply and helping me narrow this down. It's still running fine. The noise is so loud I was hoping it sounded more like a pulley, although where it's coming from, I'm afraid I'm in the market for a transmission. I'll grab the stethoscope and lay under it tomorrow. Link to comment Share on other sites More sharing options...
benjy_26 Posted December 4, 2014 Share Posted December 4, 2014 That sounds a LOT like my old Firebird's mechanical fan hitting/sfraping the shroud. I'd check that too. Link to comment Share on other sites More sharing options...
gogmorgo Posted December 5, 2014 Share Posted December 5, 2014 Yeah, definitely make sure you know where the sound's coming from before you start buying parts or pulling things too far apart. The mechanical fan on my MJ was hitting the shroud at one point and it didn't sound all that much like that, but you never know. It does sound a little bit like it might be a pulley or bearing. Maybe your starter gear isn't disengaging your flywheel somehow? A buddy and I spent almost a half hour trying to figure out where my sound was coming from at first, and neither of us were positive it was coming from the bellhousing. The stethoscope didn't help much in that. But it was very obvious where the sound was coming from when I started it up with the inspection cover off after I checked that the bolts were tight (I probably found the same forum posts and videos you did). That was when I started trying to find a crack, cause the bolts were all tight. Link to comment Share on other sites More sharing options...
gogmorgo Posted December 5, 2014 Share Posted December 5, 2014 I should also add that the running issues I experienced definitely increased in frequency. I was daily driving my MJ for about two months after first noticing the sound before diagnosing it, and continued dailying it for another five months before I finally had the time to put my daily driver (and then only vehicle) out of service for a couple days. I don't think the flexplate was in two pieces yet when I first saw the crack, and it was about two months after I saw it that I remember the first major issue I can attribute to it. Also, I'm reasonably confident my flexplate was cracked because I (and probably previous owners) put a decent chunk of mileage on it without the bellhousing properly bolted to the engine. The two were properly secured about three months before I started noticing the flexplate sound. That partial separation caused a bunch of other problems as well, and lead to excessive crank journal and thrust bearing wear, and ultimately the death of the motor about three months after I changed the flexplate... At least one of the forum posts I've seen about cracked flexplates attribute them to misalignment due to foreign objects trapped between the bellhousing and engine block. Imagine what no fixed alignment whatsoever will do... Link to comment Share on other sites More sharing options...
Hiroler Posted December 5, 2014 Author Share Posted December 5, 2014 Yeah at 300k miles who knows. Most of the parts on the truck are new though. Fan shroud and HD fan clutch are new too. I'll have a looksie tomorrow. I have another Jeep but I'd much rather be driving the comanche. Link to comment Share on other sites More sharing options...
Hiroler Posted December 10, 2014 Author Share Posted December 10, 2014 Transmission was basically starting to fall out. One bolt was sheared off. Local shop replaced two bolts, $61. Anybody in Baltimore City, I highly recommend Federal Hill Motors. Thanks again for the replies and helping to narrow this down. Link to comment Share on other sites More sharing options...
87MJTIM Posted December 10, 2014 Share Posted December 10, 2014 Transmission was basically starting to fall out. One bolt was sheared off. Local shop replaced two bolts, $61. Anybody in Baltimore City, I highly recommend Federal Hill Motors. Thanks again for the replies and helping to narrow this down. Just west of you - Frederick. :waving: Link to comment Share on other sites More sharing options...
gogmorgo Posted December 11, 2014 Share Posted December 11, 2014 Good you caught this as soon as you did. Like I said above, it was baaaad when it happened to me... And ultimately cost me significantly more than $61. Link to comment Share on other sites More sharing options...
Hiroler Posted December 21, 2016 Author Share Posted December 21, 2016 Following up - this fix worked for 500 miles but I had to replace the starter since it wasn't grabbing right anymore. The noise came back at 1k miles and grew worse so we actually pulled the transmission. Wow, what a job. New flex plate and it's quiet now, except for a small starter grind at startup. The next owner will have a much easier time getting the transmission out if needed. Those bolts had been on there for 28 years, 300k miles. Link to comment Share on other sites More sharing options...
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