1hr40 Posted June 26, 2009 Share Posted June 26, 2009 (edited) Actually The thread title should be Eibach Springs + Tokico Struts + X = bad vibration please solve for X. I have just set my car on the road and drove it 80 miles after replacing the worn springs and struts with new tokico struts and eibach springs. I also replaced the bushings with energy systems components. I did not do the moustache bar bushings yet. I also replaced the old tires with brand new set of Yokohama tires. When I first took off I felt big thumps because I did not attach the front diff mount. I fixed that and drove the car awhile. There is a vibration in the front but that might be alignment or steering rack. What I am most concerned about is the vibration from the rear of the car that seemed to be getting much worse by the end of my 80 mile test drive. It is a low frequency vibration and it gets worse at higher vehicle speeds and especially under acceleration at speed. Are the half shafts indexed to the hubs or each other? I did not mark them when I disconnected them. I searched the other posts and saw a few references to driveline angles and driveshaft u joints. I do not think that lowering the car will affect the driveline angle but it will affect the half shaft angles. The driveshaft is a newish (<20,000miles) OEM replacement done by the PO. The previous driveshaft had a bad u joint so the PO replaced the entire driveshaft. The 4 speed transmission was also rebuilt. I did spin the half shafts when they were not connected to the hubs and I could feel a kind of notchy movement. It felt like I could feel the pinion and ring gear meshing. Before the suspension upgrade I did not have this severe vibration but I do think that I could hear gear noise from the differential. The car is a 5/75 280z with 140,000 miles on it. It has been in storage since 1983. I will get under the car this weekend to make sure that the half shafts are still bolted tight. What else can I look for? Edited June 26, 2009 by 1hr40 title change Quote Link to comment Share on other sites More sharing options...
johnc Posted June 26, 2009 Share Posted June 26, 2009 (edited) If the vibration increases with vehicle speed then its somewhere in the driveline from the end of the transmission to the wheels. Check to make sure everything is assembled tight, the diff mount is installed correctly and that you didn't damage the diff mount when you forgot to tighten it down. Are the half shafts indexed to the hubs or each other? I did not mark them when I disconnected them. I searched the other posts and saw a few references to driveline angles and driveshaft u joints. I do not think that lowering the car will affect the driveline angle but it will affect the half shaft angles. Halfshafts are not indexed and you shouldn't get a vibration from the halfshafts from lowering the car. make sure your halfshafts are seated completely in the side axles. Sometimes, if you tighten the bolts down unevenly, the halfshaft mounting shoulder will cock in the side shaft. Edited June 26, 2009 by johnc Quote Link to comment Share on other sites More sharing options...
1hr40 Posted June 26, 2009 Author Share Posted June 26, 2009 Hello John, That's what I was hoping to get from this posting is a list of some things to look for when I get back under the car. I did not know that it was possible to over tighten the diff mount. The diff does not clunk any more like it did when I did the slow drive around the neighborhood. I will look at it more closely to see if anything tore or looks damaged. Maybe the moustache bar bushings got messed up? I will double check the half shafts. Since the problem seemed to get worse as the test drive went on maybe they were cocked and now they are loose. I will post my finding to help someone else that might experience this. Michael Quote Link to comment Share on other sites More sharing options...
johnc Posted June 26, 2009 Share Posted June 26, 2009 FYI... I edited my post above. You can't get the diff mount too tight unless you break a bolt. I just had a typing error above. Quote Link to comment Share on other sites More sharing options...
1hr40 Posted June 26, 2009 Author Share Posted June 26, 2009 FYI... I edited my post above. You can't get the diff mount too tight unless you break a bolt. I just had a typing error above. Hey John, Thank you - if you told me that I had to be wearing purple suspenders while using a left handed wrench to eliminate the vibration I would have gone and gotten them! I will make sure not to break the bolt! BTW there is what looks to be a home brewed chunk of metal bolted to the bottom of the front diff mount cross member. There are threaded holes for it to bolt too so maybe it is factory but the construction quality makes it look like a bunch of strips of metal were just welded together. It makes for a good jacking pad. Is it a vibration dampner? Michael Quote Link to comment Share on other sites More sharing options...
matt_w Posted June 26, 2009 Share Posted June 26, 2009 My 240Z also has that chunk of metal under the diffy mount. According to some book I read, that was a quick fix to solve vibration problems (only mounted if the customer brought the car back to the dealer to complain about it). Did you double check the strut mounts to make sure those bolts were tightened? Did you remove the differential crossmember or something? (You mentioned the mount being out). There is a band of thick rubber mounted between two bolts above the differential towards the front where the driveline connects, that may have possibly been tweaked when you put the crossmember back on. May want to double check that the diffy is sitting up against it properly. Quote Link to comment Share on other sites More sharing options...
1hr40 Posted June 27, 2009 Author Share Posted June 27, 2009 My 240Z also has that chunk of metal under the diffy mount. According to some book I read, that was a quick fix to solve vibration problems (only mounted if the customer brought the car back to the dealer to complain about it). Did you double check the strut mounts to make sure those bolts were tightened? Did you remove the differential crossmember or something? (You mentioned the mount being out). There is a band of thick rubber mounted between two bolts above the differential towards the front where the driveline connects, that may have possibly been tweaked when you put the crossmember back on. May want to double check that the diffy is sitting up against it properly. Hello Matt, I did remove the front diff mount crossmember to replace the bushings for the lower rear suspension arms. The band accross the top looks pretty loose. I thought it was some sort of a safety device in case the diff mount fails. That way the diff would not move far enough to cause permanent damage. Someone correct me if I am wrong. The rubber for the diff mount looks solid. I did notice some shiny metal around the moustache bar mount bushings. I do not remember seeing that before. Maybe when I did the slow drive around the neighborhood with the front diff mount disconnected I finished off the rear mounts. I will replace them tomorrow. The halfshafts looked good. The flanges were all nice and tight. I spun everything by hand and did not see anything unusual. Tomorrow I will get someone to sit in the car and bring it up to speed with the car on jack stands while I watch from a safe distance. Maybe I shouldn't have the car pointed at the basketball goal like it is now? Quote Link to comment Share on other sites More sharing options...
1hr40 Posted June 29, 2009 Author Share Posted June 29, 2009 I got under the car and saw that the moustache bar bushings needed replacement. Done. Car still had a bad vibration. Took the car to get the newly mounted and balanced tires rebalanced and the alignment done. One rear tire was out of balance by 2 oz. the others were out by .25oz. The front alignment's toe was way out. The car drove completely different with just a bit of vibration from the front that I will attribute to a worn steering rack bushing or some finesse with the alignment that is still needed. The rear vibration did reappear the next day. I noticed though that along with the rear vibration I could hear my brake backing plate rubbing a bit. I know that I bent the backing plate earlier. If I give the car a quick turn to the right both the brake plate rub and the vibration go away. I think that this will be the case for most stuff on this car and many other people's cars. Fix one thing just to reveal another problem. I do not think that adding the new shocks, springs and bushings caused the vibrations. I think that changing those items cleared up their problems and let me find the next wave of repairs and adjustments. I will consider this thread closed for my needs and now off to learn more about stub axle bearings and alignments! Thanks for the help from those that posted. Michael Quote Link to comment Share on other sites More sharing options...
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