matt_w Posted September 14, 2009 Share Posted September 14, 2009 I just finished putting my 73 back together. New springs/struts, an r200 with an LSD. When driving it slowly, I don't hear any noise, but once I let off the gas (doing about 5-10mph, haven't gone faster yet) there is a clunk clunk clunk sound. Not a very fast one, maybe one clunk per wheel revolution. The only suspicious thing I've found is that the rear end is about 2mm away from that torque arrestor strap mounting bar. I also jacked the rear end up in the air and let it run in 5th gear. There was a lot of vibration coming from the driveshaft it seemed like. Is it possible that the rear end is slightly off angle? Or does it sound like the problem is something else? edit: It's more of a "knock" than a "clunk". I tried grinding down the ridge in the torque arrestor mount to give me more than 2mm clearance, but that didn't fix it. Quote Link to comment Share on other sites More sharing options...
softopz Posted September 15, 2009 Share Posted September 15, 2009 are your springs set in the insulators right like where the coil ends. ? another thing is exhaust? when I did the r200 conversion I found the hangers that connect the control arms ( the rear part of it) are literally touching the mustache bar. Quote Link to comment Share on other sites More sharing options...
trwebb26 Posted September 15, 2009 Share Posted September 15, 2009 Need to find out more about the noise in order to narrow it down some... Does it only do it when you are stopped? Does it do it more turning left vs. right at a slow speed? Does it do it in reverse? Does it do it when you go over bumps? Is it a metal on metal sound - or more muffled? What stub axles are you running? Do the U-Joints look like they are in good shape (if you are running regular U-Joint stub shafts)? What kind of diff mount are you using? Make sure all the driveshaft and stub axle bolts are tight. Are you certian it isn't a gear noise from the diff? Quote Link to comment Share on other sites More sharing options...
Zmanco Posted September 15, 2009 Share Posted September 15, 2009 One of the guys here in CO had a similar issue and it turned out one of the nuts holding the mustache bar was loose. Worth checking ... Quote Link to comment Share on other sites More sharing options...
matt_w Posted September 15, 2009 Author Share Posted September 15, 2009 Thanks for the replies thus far. I've played around with it a lot more and have more info. First of all, here is my setup: Tokico struts, eibach springs. new ujoints/rebuilt halfshafts R200 rear end with OBX LSD All bushings replaced with poly Some of the obvious gotchas that I've checked: Ebrake cables rubbing on driveshafts Mustache bar bolts (I used loctite on them) Exhaust (about 1/2 inch of clearance between exhaust and rear end) halfshaft clearance while suspension is under load The knock only happens when not accelerating. So either coasting in neutral, or not giving it any gas. It sounds like something is hitting a driveshaft as far as the frequency that it happens. It's not super loud (somewhat muffled), but it's there. Also, to answer softopz, the springs are about 1/4" from the end of the insulators. This is what Eibach recommends. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 15, 2009 Share Posted September 15, 2009 Under load the nose of the diff lifts, under decel it is pulled down. That makes it pretty unlikely that it is the driveshaft itself hitting anything. This is a good one... Quote Link to comment Share on other sites More sharing options...
matt_w Posted September 15, 2009 Author Share Posted September 15, 2009 Sorry, I meant the frequency is like something is hitting a halfshaft, not the driveshaft. Quote Link to comment Share on other sites More sharing options...
matt_w Posted September 15, 2009 Author Share Posted September 15, 2009 Unless it's something wrong inside the diffy, it almost HAS to be a halfshaft if it's clunking at that frequency doesn't it? The ujoints I got for the halfshafts have those long grease fittings, I wonder if one of the joints is bumping against those? Perhaps under deceleration, the suspension changes just enough that the angle change of the half shafts is causing the ujoints to rub against the fitting. I'll look under there tonight and see. Quote Link to comment Share on other sites More sharing options...
trwebb26 Posted September 18, 2009 Share Posted September 18, 2009 I mentioned in my previous post about checking turning left versus right... With a limited slip it won't be as easy, but turn while accelerating and see if it happens more one direction vs. the other. If it happens when turning the car to the right - check the left halfshaft.... If it happens when turning the car to the left - check the right halfshaft. Quote Link to comment Share on other sites More sharing options...
matt_w Posted October 5, 2009 Author Share Posted October 5, 2009 Finally had more time to look at this problem again. It seems to be the same frequency whether I'm turning left or right. One other thing I noticed is that the knocking goes away under 5mph. Checked closely anything that would be touching the mustache bar, half shafts, or diffy. Do you think it's possible that the LSD could be causing it? I've never heard of one causing an issue like this, but who knows. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 5, 2009 Share Posted October 5, 2009 Finally had more time to look at this problem again. It seems to be the same frequency whether I'm turning left or right. One other thing I noticed is that the knocking goes away under 5mph. Checked closely anything that would be touching the mustache bar, half shafts, or diffy. Do you think it's possible that the LSD could be causing it? I've never heard of one causing an issue like this, but who knows. The LSD ONLY works when you're turning. If you're going straight and getting the noise, it isn't the LSD. Could be a ring and pinion issue like a chip in one gear or the other), but that's unlikely. Not impossible, but unlikely. I'd look at the sway bar end links and make sure that there is clearance between them and the halfshafts. Quote Link to comment Share on other sites More sharing options...
trwebb26 Posted October 5, 2009 Share Posted October 5, 2009 One thing I was thinking about... make sure your ebrake cables aren't rubbing on a shaft somewhere - including those up above the main driveshaft. Quote Link to comment Share on other sites More sharing options...
John Scott Posted October 5, 2009 Share Posted October 5, 2009 This is out there, but maybe worth mentioning. Years ago I had a bind in a u joint that only presented under deceleration. As I recall, was more of a shudder than clunk. Also look for shiny/ wear spots on anything that rotates, all the way up to the transmission that would indicate contact. Did you use a new diff mount? Was the diff opened for the LSD install? Slim possibility that one of the ring gear bolts is making contact in the case? Recheck all flange, 1/2 shaft and drive shaft bolts to insure that none were binding, all mating surfaces show no gaps. Quote Link to comment Share on other sites More sharing options...
matt_w Posted October 5, 2009 Author Share Posted October 5, 2009 Wow, thanks for the quick replies. The diff mount is newish, I didn't swap it when I put the new diff in. I know, I know, I really should have. I put the LSD into the diff myself, and did a complete backlash/runout check after, and adjusted the shimming. It definitly doesn't rub anywhere, and all the teeth look to be in good condition. I also don't have the rear sway bar in right now, and the e-brake cables have already been adjusted for the lowered suspension to not rub. I happen to have 2 spare halfshafts, so I think I'm going to swap out one at a time to see if that fixes it. I think John S might be onto something with the ujoint theory. I may not have pressed them in perfectly when I rebuilt my halfshafts. Quote Link to comment Share on other sites More sharing options...
Zerocell5688 Posted October 5, 2009 Share Posted October 5, 2009 This may seem kinda silly but you might wanna check that your real tires are bolted all the way on and secure. I had a nasty noise issue with my car making a terrible grind grind noise after i changed by u-joints turned out the tire on the drivers side rear was loose and my rim was eating my wheel studs lol. it may sound silly but it turned out thats what it was. Just throwin that out there for ya. ~J Quote Link to comment Share on other sites More sharing options...
matt_w Posted October 10, 2009 Author Share Posted October 10, 2009 I swapped out both halfshafts with some untouched ones off a 79ZX, and it's still knocking Also, I emptied out the differential fluid (It's been about 2-300 miles since I put in the LSD and re-shimmed it). There was a noticeable amount of fine metal flakes in there. Is that expected? I would guess it would be, but who knows. I'm running out of ideas. Short of something being fubar inside the diffy, the only other thing I can think of is the driveshaft not liking the slightly different angle of the R200, and going into some kind of weird vibrational mode. Quote Link to comment Share on other sites More sharing options...
82boxima Posted October 18, 2009 Share Posted October 18, 2009 I had this same issue on my maxima... it's all 100% stock, so I wouldn't know about the LSD or any other swapped part causing that noise... I did notice some of my bushings towards the rear of the car were in bad shape, and started slowly replacing them with " better ones" from a 280zx that was at my local junk yard. I figured out it was the passenger side moustache bar mount.. it LOOKED ok and tight, tried giving it a turn with the ratchet and the old bushing came crumbling out in many pieces.. I could see where it had been moving up and down on the bolt by about 1/4 inch:shock:....fitted the " better " bushings in there, and it made the noise go away... just a thought. Quote Link to comment Share on other sites More sharing options...
matt_w Posted October 22, 2009 Author Share Posted October 22, 2009 Hmm...Do you think the rear springs could be causing the noise? I was just toying around with the rear, and I noticed that several of the coils are compressed and touching eachother (when I push from the side, I can feel that they are binding on eachother). I am running the Eibach lowering springs for the 240z, but I have an R200 with an additional 20 pounds or so from the LSD. Converting to rear discs, removing the spare tire and rear bumper should have freed up some weight though. I wonder if it's normal for them to be so compressed? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 22, 2009 Share Posted October 22, 2009 Hmm...Do you think the rear springs could be causing the noise? I was just toying around with the rear, and I noticed that several of the coils are compressed and touching eachother (when I push from the side, I can feel that they are binding on eachother). I am running the Eibach lowering springs for the 240z, but I have an R200 with an additional 20 pounds or so from the LSD. Converting to rear discs, removing the spare tire and rear bumper should have freed up some weight though. I wonder if it's normal for them to be so compressed? Progressive springs are commonly coil bound or very nearly coil bound for the first several coils when the car is sitting with it's weight on the suspension. That's not it. Quote Link to comment Share on other sites More sharing options...
streeteg Posted October 22, 2009 Share Posted October 22, 2009 I have the same issue on my car--- except the clunk only comes on deceloration once when i let off--- as a result of momentum. It doesnt continue to clunk on decel.... My best assumption is the bushings on the mustache bar--- so I have a new set coming t osee if that helps. Keep me posted on anything you find though... Id be happy to figure it out without having to pull the stupid mustache bar off to press in new bushings. -Eric Quote Link to comment Share on other sites More sharing options...
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