zane9000 Posted August 8, 2006 Share Posted August 8, 2006 So, when I step on the gas I hear a loud clunk coming from the rear. Also while I am cruising at low RPM I get a loud rattle from the same area. I did a search and came up with 3 things that could be wrong, mustache bar bushings, U-Joints, or diff mount. What can I look for and what type of tests can I do to get a better idea of whats broken? Thanks, Warren Quote Link to comment Share on other sites More sharing options...
b__sosick Posted August 8, 2006 Share Posted August 8, 2006 does this ever happen in neautral while coming up on a light or stop sign (-5 mph)? i keep hearing a scary rattling noise every time i slow down to about 5 mph . neautral or otherwise! Quote Link to comment Share on other sites More sharing options...
zane9000 Posted August 8, 2006 Author Share Posted August 8, 2006 Nope, the only time I hear the noise is an initial clunk when I hit the gas and a rattle when I try to maintain my speed. Under heavy accel and no accel there is no noise. Also there is no noise regardless of what I do in neutral. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 8, 2006 Share Posted August 8, 2006 I was never really able to check U-joints while the halfshafts were in the car. I mean if they're broken you'll probably be able to look at them and see it, but if they're loose you have to grab the shaft at both ends of the joint and twist back and forth and feel for slop. Much easier to do with the shaft out of the car. For the diff mount put a pry bar between the front of the diff and the crossmember and see how far the front of the diff lifts up and if the rubber in the mount is torn. If it lifts up a lot check the rubber in the mount to see if it's torn, also check the strap that goes over the front of the diff and check for tearing. On the mustache bar bushings I don't really know a test you can do to test them, but if they're original you can bet they could use replacing. Quote Link to comment Share on other sites More sharing options...
zane9000 Posted August 9, 2006 Author Share Posted August 9, 2006 Thanks for the tip. I will check out the diff tomorrow. I usually jack the car up by the diff though, so I will have to find another way to get under there I suppose Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted August 9, 2006 Share Posted August 9, 2006 Most likely bad U-joints. My new driveshaft rear U-joint has worn considerabally over the last 4k miles. It has a little bit of slop. I think it is from hard acceleration twisting the diff around. It was old moustache bar bushings and a new diff mount. I think the stock diff mount is too flexy. Maybe I can modify it to not push up. Quote Link to comment Share on other sites More sharing options...
deja Posted August 9, 2006 Share Posted August 9, 2006 I have that too. I've heard this is fairly common on Z cars. If I'm careful to get a smooth up shift its fine but the least hard clutch release causes the thump. It never does it on down shifts. Mine will also make that horrible noise if I let the engine get too low in RPMs and it starts to lug, sounds like the whole rear end is falling apart. Some say get a solid diff mount to fix it, some say that will transfer a lot of noise. I know there is some play, probably too much in the rear driveshaft U-joint too, that will be fixed when I do the LT1 swap. Quote Link to comment Share on other sites More sharing options...
datman Posted August 10, 2006 Share Posted August 10, 2006 I just wrote a very long post on this knocking noise but it seems to gone I fixed my knocking by cleaning all the faces of the half shafts, use a file to make sure there are no high spots and fit new bolts and nuts. I also fitted new rear wheel bearings and torqued to 200lb/ft although the old bearings seem to be fine I'd heard of them causing stramnge noises also check there is no play between the brake drum and the wheel studs, I could move my drum a few mm and hold the half shaft still because the holes had enlarged.I'd also clean the face of the drum and the back of the wheel to ensure there is no slip. before all this I changed the half shaft joints....no change changed the diff...no change bushes...no change. Quote Link to comment Share on other sites More sharing options...
zane9000 Posted August 10, 2006 Author Share Posted August 10, 2006 Thanks to everyone who is chipping in. I took the car out on the highway this evening for the first time in 6 months (The car was parked during a motor swap/megasquirt install). When I got up to highway speeds there is a really terrible vibration/rattling coming from the rear end. It is so bad it sounds like the car is going to shake apart. Does this give anyone any further insite to my problem? Quote Link to comment Share on other sites More sharing options...
datman Posted August 10, 2006 Share Posted August 10, 2006 yep mine did the same at anything over 70mph Quote Link to comment Share on other sites More sharing options...
datman Posted August 10, 2006 Share Posted August 10, 2006 you can jack the car up, run the engine and engage 5th gear, hold one wheel and see if the vibration is coming from the other side or it could be the prop has been put back on in the wrong position. Be careful you have the car on stands....would be messy if it hit the floor doing 70:shock: Quote Link to comment Share on other sites More sharing options...
zane9000 Posted August 10, 2006 Author Share Posted August 10, 2006 LOL, yea, messsy... I already droped the car with both front wheels off :S Im going to take it to a local shop that I know tomorrow. The owner said she can put it on the rack and run the car to pinpoint the problem. I will post the results when I find out what she says. Quote Link to comment Share on other sites More sharing options...
zane9000 Posted August 14, 2006 Author Share Posted August 14, 2006 turns out i had 6 bad ujoints and a bad wheel bearing :S Quote Link to comment Share on other sites More sharing options...
deja Posted August 14, 2006 Share Posted August 14, 2006 turns out i had 6 bad ujoints and a bad wheel bearing :S Holy crap! That's going to be expensive, but with a 33 year old car that's to be expected I guess. Quote Link to comment Share on other sites More sharing options...
zane9000 Posted August 14, 2006 Author Share Posted August 14, 2006 it is going to run me about 500. not too bad i guess. It would be alot cheaper to do it myself, but i really need it done quickly Quote Link to comment Share on other sites More sharing options...
datman Posted August 14, 2006 Share Posted August 14, 2006 After messin with my rear springs this weekend my clunk came back!! It turned out to be the halfshaft to stub axle flange bolts not quite tight enough.....cranked them up nice and tight and its all quiet again. Quote Link to comment Share on other sites More sharing options...
PUSHER Posted August 14, 2006 Share Posted August 14, 2006 How much is it to fix a ujoint? Like if I take the axle out myself and just bring it to a mechanic. Quote Link to comment Share on other sites More sharing options...
zane9000 Posted August 14, 2006 Author Share Posted August 14, 2006 if you take the axel out yourself you might as well just replace the ujoint on your own. from what i understand there isnt a whole lot to it, just a few bolts. I think Im paying like 35-40 dollars each joint Quote Link to comment Share on other sites More sharing options...
datman Posted August 15, 2006 Share Posted August 15, 2006 replaced mine, its very easy, you have to pry out 4 cir clips from the ends of each joint and then hit the caps out. They can be in very tight. There are a few cars that share the same joint...I think the small suzuki jeeps use them. Quote Link to comment Share on other sites More sharing options...
zero Posted August 15, 2006 Share Posted August 15, 2006 does this ever happen in neautral while coming up on a light or stop sign (-5 mph)? i keep hearing a scary rattling noise every time i slow down to about 5 mph . neautral or otherwise! I have that clunk. As soon as I get on the brake, sometimes i get an initial clunk followed by scary rattling. CLUNK..dun..dun..dun..dun. The diff seems like it could be a little loose, but I''m not sure what kind of play its supposed to have. If the car is off the ground and I put a jack under the front of the diff, it moves maybe a centimeter as I jack it up. but i dont really know how much it is suppoed to move. the front of the diff also seems to be significantly closer to the passenger side of the tunnel than the driver side, but I figured that was normal because the handbrake mechanism is on the drivers side. Quote Link to comment Share on other sites More sharing options...
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