terrawombat Posted March 30, 2010 Share Posted March 30, 2010 Not a Comanche, but the drivetrains are near identical. Posted the same issue on NAXJA, but I'm talking to myself over there: http://www.naxja.org/forum/showthread.php?t=1028978 Anyway - long story short, I'm getting a very distinct tapping noise somewhere near my feet that is consistent with the speed of the vehicle, not engine RPM. It will only happen when my foot is off the gas and the vehicle is decelerating. The tapping seems to die down some when the vehicle is put into 4wd-Hi and is almost non existent in 4wd-Lo, but it could be that while in 4wd-Lo, there is so much driveline noise and whining that I'm not even hearing the tapping. My first thought was, obviously, u-joints, but I crawled underneath last night and tried to shake, wiggle, and rattle every driveshaft and axleshaft under the truck. The u-joints all seem extremely tight and the only one that may have exerted a tiny bit of movement was the front passenger axle shaft u-joint. I also replaced the transmission mount for good measure. I bought the thing months ago and this was a good reason to finally install it, but to be honest, I think the old, 167k mile tranny mount was stiffer than the brand new one from Jeep. It also did nothing to fix the original issue at hand :dunno: The only thing that struck me as odd was the amount of play in the front driveshaft. I had all four wheels of the Jeep on the ground and it was in 4wd-Hi at the time, but I could still rotate the front driveshaft a solid 3/8"-1/2" in either direction. I checked on my '98XJ (it's nice to have near identical vehicles around for additional troubleshooting!) and it seemed to have a similar, although a little less, amount of slop in the front driveshaft (that vehicle has 74k miles on it). I think I'm going to wind up buying all new u-joints for the vehicle anyway. I believe all of the ones are there are the originals and I'd like to get greaseable ones so that I can have some level of control with them. However, I don't believe that it's going to solve the issue as all of the current ones seem pretty tight. Does anyone else have any other suggestions or troubleshooting tips I could use to narrow this down further? Is the amount of slop in the front driveshaft normal? Link to comment Share on other sites More sharing options...
88mjmanche Posted March 30, 2010 Share Posted March 30, 2010 its a 231 transfercase right. if so your chain inside the case might be getting old but that seems weird to me :dunno: mabey a bad bearing in one of the output shafts on the transfer case :dunno: just some things i have seen happen before Link to comment Share on other sites More sharing options...
Eagle Posted March 30, 2010 Share Posted March 30, 2010 How many miles? I have been noticing a tapping in my wife's 2000 XJ. I'm pretty certain it's caused by the exhaust pipe (not the tail pipe) hitting the cross member. If so, it means the cushions in the tranny mount are getting compressed. Link to comment Share on other sites More sharing options...
terrawombat Posted March 30, 2010 Author Share Posted March 30, 2010 How many miles? I have been noticing a tapping in my wife's 2000 XJ. I'm pretty certain it's caused by the exhaust pipe (not the tail pipe) hitting the cross member. If so, it means the cushions in the tranny mount are getting compressed. I have 167,250 miles on the '01 XJ. When does the tapping occur on your wife's vehicle? Once it dries out a little bit here (we just got dumped on with rain), I'm going to remove the front driveshaft and see if that makes any difference. Link to comment Share on other sites More sharing options...
terrawombat Posted March 30, 2010 Author Share Posted March 30, 2010 Figured it out just now. Kind of embarrassing but figured I should get it out there in case anyone runs into the same problem. It turned out to be REALLY loose lugnuts on the left rear wheel. The sound I was hearing was the rim slapping around while coasting. In fact, I went and retorqued ALL of the lugnuts to 120 ft-lbs and there were at least three loose on each wheel. Scary stuff, glad I caught this relatively early and didn't just write it off as another "Jeep sound." The clue was that it was getting progressively worse in a short amount of time. I first started noticing it Sunday evening and on my way home from work today, it was definitely getting louder - probably put about 25 miles on it since I first noticed the sound. The rim that was real loose doesn't seem to be damaged, but I'll definitely be keeping a close eye on it from now on...probably retorqueing the lugs every few days! Once I narrowed down the problem, I did a search over on NAXJA and found a member that had the exact same problem as me! He was a bit embarrassed too: http://www.naxja.org/forum/showthread.php?t=1004379&highlight=loose+lugnuts. Also, the last guy that posted mentions how the alloy rims need constant retorqueing. Yep, definitely got a set of those on this truck: Link to comment Share on other sites More sharing options...
Eagle Posted March 31, 2010 Share Posted March 31, 2010 In fact, I went and retorqued ALL of the lugnuts to 120 ft-lbs and there were at least three loose on each wheel. ... I'll definitely be keeping a close eye on it from now on...probably retorqueing the lugs every few days! I strongly suggest that you NOT do that. Especially if you're going to be checking them to 120 ft-lbs. You'll pull the lug nuts right through the rims within a month. The FSM specifies 85 to 115 ft-lbs as the service torque for lug nuts. Among all the XJs and MJs I own and have owned, I must have put on close to a half million miles (the '88 XJ along has 287,000 on it). I always use a torque wrench, and I always torque to 85 to 90 ft-lbs ... no more. I have NEVER had one loosen up on me. I HAVE seen lug nuts pull right through the wheel as a result of obsessive re-torquing. It happened to one of the guys in the old Javelin/AMX Sports Car Club. He autocrossed with us, and he would go around and re-torque his wheels after every run. One season was all it took -- actually, he didn't even make it one season. It was an expensive mistake, too, because he had more money than brains and the wheels he ruined were custom-made racing wheels. If you must check the torque every few days, be sure to use a torque wrench and aim for the low end of the allowable range rather than a setting that's over the top of the high end. Link to comment Share on other sites More sharing options...
terrawombat Posted March 31, 2010 Author Share Posted March 31, 2010 The lugnuts on these rims were originally torqued to 90 ft-lbs when I got them about 3000 miles ago. I suppose my mistake was not checking them during that time to make sure they stayed snug, but I've never once had this problem on any of my other vehicles - Jeep or not, aluminum rims or steel. I'll take them back down to 90 ft-lbs, but I'm still keeping a very watchful eye on them. Link to comment Share on other sites More sharing options...
terrawombat Posted March 31, 2010 Author Share Posted March 31, 2010 Lugnuts back to 90 ft-lbs. Constant checkups scheduled... Link to comment Share on other sites More sharing options...
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