Guest bastaad525 Posted April 21, 2004 Share Posted April 21, 2004 Okay, been noticing this one lately, and it's getting worse. I get this rattle/vibration, from the rear of the car. Only under acceleration, only at 1500rpm. Of course it usually only happens in 1st gear as I'm leaving a light, but sometimes if I shift way early or something like that it will do it in other gears too. Only when accelerating, when slowing down, nothing, and I tried to get it to keep buzzing by holding the revs at 1500, cruising slow, and it kinda did and kinda didn't. It wont do it if I rev the car in neutral, only when moving. it's coming from the rear of the car, sounds like outside, not inside. I checked all the bolts holding my exhuast up and they were all tight. Checked my license plate and the tail light panels. Checked all around the fuel tank and rear suspension for any loose bolts and I saw nothing, and I didn't really see anything that makes sense for making that kind of noise. I originally assumed that it was eitehr the exhaust rattling or my license plate rattling... that's the kind of noise it is. But I checked both and got nothing. Even took the license off just to see and it still did it. My only other guess is maybe something INSIDE my glasspack rattling around? But I know that's a long shot, and it does sound more towards the middle or possibly even the passenger side anyways Well... just shoot some ideas my way if you have any... I just dont know what else to check, but that noise is driving me nuts OH and it seems to be worse when the car is cold but I think that MAY be that I drive it more gently when it's cold, leaving lights slower, but it does it all the time cold or warm. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted April 21, 2004 Share Posted April 21, 2004 Driveshaft U-joint. If this weren't the internet I'd put $20 on it. EDIT- I suppose I should clarify. My friend's Z has a vibration on acceleration at low rpms, you can feel it in your butt thru the seat more than anything else. Turns out she ran her front driveshaft U-joint dry for who knows how long, and that was the cause. Quote Link to comment Share on other sites More sharing options...
tannji Posted April 21, 2004 Share Posted April 21, 2004 is it a heavy rattle, from something solid, or a lighter rattle? I had the same problem, from the hatch, took the inner faceplate off, tightened everything, ended up wrapping a couple of things, and it went away. Also had a fuel pump make the strangest sound, only when hot, under load. took me forever to find that one. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 23, 2004 Share Posted April 23, 2004 jmortensen - while I dont put any large amount of faith in the U joints I have (though, I believe they are less than a year old?) it seems kind of odd for it to only do it at 1500rpm like that, and only on SLOW acceleration. If I move from the light at even a reasonable (read: normal) speed it doesn't do it. It happes most when the car is cold as I drive it much more gently until it's fully warmed up. Also, it definately seems to be coming from farther back than that, at the very rear of the car... no farther forward than say halfway between the very rear of the car and the middle of the fuel tank, I'd say. I will take a look at them however, just to be sure. tannji - I guess I'd say it's more of a light, buzzy rattle... really a loud buzz, not like clunking. It was weird, I thought I'd had it nailed when I tapped on my license plate and found that it made a noise that sounded identical to me, but then I jammed some paper towels up under the plate to keep it from making contact with the rear panel, and it would still make the noise. Maybe it's the center rear panel? I thought it might be somethign inside the car as well... what all should I check? Tail lights are secure... I didn't really know what else to check. The sound definatley sounds like it's coming from outside the car rather than in. I dont think its the fuel pump but I guess it could be coming from that area. It seems to be getting worse, more common and louder, so I'm really worried that something is working it's way loose and is gonna end up falling off!! Again... I did check all the bolts I could see/get to with the car on a lift and they all seemed fine. I'll check the U-joints and take a look around the inside of the hatch and rear inside of the car. Keep any suggestions or "hey when it happened to me THIS is what it was" ideas coming. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 25, 2004 Share Posted April 25, 2004 Well it's not the U-joints, they seem fine, and anyways I just realized... it couldn't be the U-joints... this rattle always happens at specific engine RPM, not road speed.... it happens in any gear at about 1500rpm. But it's definately not coming from ANYWHERE near the engine. Definately in the spare tire/fuel tank area or the rear of the car. I looked in my spare tire well and there was a LOT of crap in there, bolts and stuff... I hoped after I cleaned it out that the rattling would stop, but its still there. Maybe somethings loose in the exhaust... every time I get rattles like this it ends up being the exhaust... but again, all my exhuast mounts are tight and the rubber bushings still look great. Just seems odd to have an engine related vibration near the rear of the car and have it NOT be the exhaust.... Quote Link to comment Share on other sites More sharing options...
datsunlover Posted April 25, 2004 Share Posted April 25, 2004 Do you hav a cat on the car? Could a piece of catylist (sp?) be rattaling/loose and making noise at only certain (under load) RPMs? Or maybe the noise of the car after that RPM drowns it out? Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 26, 2004 Share Posted April 26, 2004 No cat. I keep going back to something in the exhuast though... all I have is a glasspack, placed where the stock muffler would be. Today I had a friend come listen while I revved it, in gear, slipping the clutch while holding the brake. First thing we found out... my clutch doesn't like to be slipped that much! Man it was making a LOT of noise. It started making a grinding noise as I kept slipping it. BUT, that wasn't the noise that I've been hearing... He could also here that buzz/rattle sound, seperate from the sound the clutch was making, but to him he says it sounded more like it was coming from the middle of the car, maybe the rear of the tranny, driveshaft or diff area. Again... this baffles me... I've had u-joints go bad before and they always just make a clunking noise. And how a bad U-joint would rattle/buzz at a given RPM, in every gear, but NOT at a given road speed, is beyond me. I'm going to try to get the car back on the lift hopefully tommorow. I really hope this doesn't end up being something major like a bad tranny or something.... Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 26, 2004 Share Posted April 26, 2004 Not sure if this makes any difference today, but I found out I CAN get it to make the sound if I rev it in neutral, thought before it would only do it in gear. It wont do it if I slowly bring up the revs, like it will when Im' just cruising slowly, but if I jab the throttle it will buzz for a split second. Still sounds to me like it's coming from the mid-rear of the car, my friend said it sounded like the area right about under the seats... I will try to get the car on a lift again asap but I dont know what to look for right there. at least I can eliminate the drive shaft and half shaft and u-joints, and the differential.... maybe it's something rattling around IN the tranny? Or the clutch? maybe something stuck IN the exhaust?? very frustrating..... Quote Link to comment Share on other sites More sharing options...
Phantom Posted April 26, 2004 Share Posted April 26, 2004 It sounds like a harmonic with the specific engine RPM - first place I would look is the exhaust system to see if a hanger is loose or it is touching a body member at some point. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 27, 2004 Share Posted April 27, 2004 yeah that's what I keep thinking... exhaust.... I did check the hangars already and they were both bolted tight, and both have rubber insulators on them to dampen vibrations. I didn't see that it was touching the body at any point, but I admit I wasn't looking too closely for that. Hopefully on thursday (my day off) I can get it back over to the exhaust place and have them lift it again for me and figure it out once and for all. Quote Link to comment Share on other sites More sharing options...
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