madkaw Posted August 30, 2011 Share Posted August 30, 2011 I have a high speed driveline vibration around 100mph. It almost sounds like it has a rhythm to the vibration. I am running a 82 T-5 to a r-200. The driveshaft was supposedly balanced at the time I modified the shaft for the T-5 swap. I have also had the half shafts balanced recently. I am running the Rt mount and think I have driveshaft set-up right as far as angles. I modified my original trans mount to adapt to the T-5. I believe I might have compromised the integrity of the rubber on the mount since I welded on it. I can push up on the tail shaft and get movement without much effort( one arm push up). I guess my question here-would a loose trans mount just exacerbate a vibration or actually be the cause of the vibration? I was considering a modification of the mount to secure the tranny tighter to the mount-is there any consideration with that? Quote Link to comment Share on other sites More sharing options...
Tony D Posted August 30, 2011 Share Posted August 30, 2011 It can actually be the cause. This was EXACTLY what caused it in my 260Z. It was not present in a form I could feel in lower gears, but at over 80mph there was a vibration that got BAD. The tranny mount was letting the tailshaft lift up under load and the angularity introduced only during these high-load excursions was very pronounced. At lower speeds in lower gears it simply was either passed through too quickly to notice, or was not loaded enough to delfect the tailshaft upwards enough to be an issue. Tie the back of the tranny down so it can't change your driveshaft angularity, and you should cease having that problem if your driveline angles are otherwise correct. Quote Link to comment Share on other sites More sharing options...
Leon Posted August 30, 2011 Share Posted August 30, 2011 It can actually be the cause. This was EXACTLY what caused it in my 260Z. It was not present in a form I could feel in lower gears, but at over 80mph there was a vibration that got BAD. The tranny mount was letting the tailshaft lift up under load and the angularity introduced only during these high-load excursions was very pronounced. At lower speeds in lower gears it simply was either passed through too quickly to notice, or was not loaded enough to delfect the tailshaft upwards enough to be an issue. Tie the back of the tranny down so it can't change your driveshaft angularity, and you should cease having that problem if your driveline angles are otherwise correct. That is exactly what I've been getting in my 260Z around 75mph, it happens under load but seemingly moreso at lift throttle conditions. Looks like I'll have to check out my mount as well. The diff is strapped down tight. Quote Link to comment Share on other sites More sharing options...
madkaw Posted August 31, 2011 Author Share Posted August 31, 2011 I thought it had too much play for my liking. I probably loosened the rubber when I welded on new tabs to the mount. I tried to use a heat sink, but who knows it might already been bad. I had come up with a cable set up that I could run over the top of the tailshaft and moored at the mount using eye/bolts, but hadn't got around to hooking it up. This maybe also why I still get some clunk noise while blipping the throttle at lower rpm. Thanks for the conformation on that---aahhh-another thing on the to-do list. Quote Link to comment Share on other sites More sharing options...
Tony D Posted September 1, 2011 Share Posted September 1, 2011 Let us know what happens and how bad it really was---photos would be nice. Mine was completely separated when I got under there to check. Quote Link to comment Share on other sites More sharing options...
madkaw Posted February 14, 2012 Author Share Posted February 14, 2012 Well I'm reporting back in on this issue and it's NOT resolved. I did moor the rear of the tranny down against the mount. I actuallu used a cable set-up(sorry no pics at this time), but it did eliminate the movement of the rear of the tranny. I still have the vibration and now I guess I am back to the driveshaft. I had the T-5 shortened by a reputable driveshaft specialty shop, but I question just the same. It seems the only thing left to try. I have had the half shafts checked and have my Subbie diff installed and still the same issue. Maybe the shop didn't get the drive shaft set-up right. I checked driveline angle and to the best of my knowledge i found that thr RT mount didn't put th diff at a low enough angle, so I lowered it-this was a while back and didn't change anything. The reason I think that my set-up was different and needed the change is because my custom tranny mount for the T-5. I am going to reset the RT mount back to stock setting and try once more. The driveshaft shop is equipped to measure and check this also, which is what i will probably will have done. Quote Link to comment Share on other sites More sharing options...
madkaw Posted February 16, 2012 Author Share Posted February 16, 2012 Took the DS back to the shop and had it rechecked and wouldn't you know it ran perfectly balanced on their machine. So I'm taking the car in and have the shop check the driveline angle. I had made a change to the RT mount angle based on my measurements and it vibrates there, so I'm changing it back to the RT angle and taking to the shop. Quote Link to comment Share on other sites More sharing options...
Tennesseejed Posted February 17, 2012 Share Posted February 17, 2012 Might not be driveline related. A faulty shock or strut can manifest as high speed vibration. So can bad tires or a missing counterbalance weight that fell off. Have you tried driving at a speed where you notice the vibration and then putting the car in neutral and coasting? Might help some with the diagnosis. Quote Link to comment Share on other sites More sharing options...
madkaw Posted February 19, 2012 Author Share Posted February 19, 2012 Good advice and i will keep that in mind. Took the car into the DS shop and they put it on the lift and checked the 'angle of the dangle'. With the RT mount in the originally configured position the shop said it was good to go-very good they said! Sooooo, my adjustment was obviously fu@ked up and I don't know how to measure that angle properly. My adjustment involved lowering the nose of the diff a good 1/2" or better-which on a 30" DS was too much. Now wouldn't you know the vibration is much better now. I took the car up to 115mph and it was fairly smooth. I believe I still have work to do in other areas, but I feel much better KNOWING that the angle is right and the DS is balanced. Elimanating that stuff makes troubleshooting better and easier. It's nice to know that since I made my own RT mount that I did that right. A comment was made by the tech about NVH. He implied that I will always here more noises and feel more vibrations because the way my car is set up. He was probably refering to my semi solid trans tailshaft mount and my semi rigidly mounted exhaust. Quote Link to comment Share on other sites More sharing options...
madkaw Posted August 12, 2012 Author Share Posted August 12, 2012 (edited) Well, I am back to this issue that hasn't been resolved. Latest updates is that I DID have a bad halfshaft on the passenger side. There was excessive play between the casing and the spline. I replaced the shaft with another one and had the universals changed out. I believe it mostly eliminated the high speed vibration that was there at constant speed, but I obviously have more then one issue. It's still amazing to me that the DS shop can balance a bad halfshaft. I still have a rhythmic vibration around the 3k rpm range. It is most noticeable during deceleration. It has been very subtle until recently. Recently I had shoved my diff foward about 3/8" . The reason I did this was that my previous install of the diff I shoved it too far back and the moustache bar was about riding against my downlinks to the rear control arms. My RT mount does allow for some foward aft adjustment. Being shoved too far back caused contact with any flexing of the moustache bar and I was getting a clunk in the rear. Anyway, after moving the diff FOWARD, the vibration has gotten more intense. So can someone help me picture what is going on as far as driveline forces during decel? What changes occured in my driveline moving the diff like this. Edited August 12, 2012 by madkaw Quote Link to comment Share on other sites More sharing options...
NewZed Posted August 12, 2012 Share Posted August 12, 2012 Word is that 240Zs with 280Z R200s and half-shafts can bind the half-shafts when the suspension is compressed and/or the car lowered. The half-shafts run out of travel. There are even directions out there for increasing the travel on the inside portion of the ball tracks in the half-shaft, the area that was was damaged on your other half-shaft. If your car is lowered maybe you're bound up and it's causing vibration and half-shaft damage. Look at the betamotorsports site for a good description of the problem. I think it's in the bench-racing section. Quote Link to comment Share on other sites More sharing options...
madkaw Posted August 12, 2012 Author Share Posted August 12, 2012 You have reminded me to update my signature. I am running the STI r180, so that's not issue. My car is only lowered 1 inch . I would be more worried about running out of travel on my main driveshaft. Not sure what the minimum amount of play should be on the yoke at the tranny. Quote Link to comment Share on other sites More sharing options...
SUNNY Z Posted August 23, 2012 Share Posted August 23, 2012 You have reminded me to update my signature. I am running the STI r180, so that's not issue. My car is only lowered 1 inch . I would be more worried about running out of travel on my main driveshaft. Not sure what the minimum amount of play should be on the yoke at the tranny. Thats a GREAT place to look. I had a nasty vibration that I tracked down to be the output shaft bushing. Its the little babbit bushing that supports the slip yoke in the tailshaft of the transmission. I also had a rather disheartening vibration around 100mph. Once I switched to CV axles and got rid of those U-joint junks of junk, it feels 10x more stable in the triple digits. Quote Link to comment Share on other sites More sharing options...
madkaw Posted August 23, 2012 Author Share Posted August 23, 2012 How does one check that output bearing? I have the DS off. It seemed that with the DS installed I could get movement at the tailshaft. When I take the DS off, I can wiggle the output spline easily with two fingers-but I thought that was okay without the DS yoke on there. Like I said though, I can wiggle the DS yoke with the DS in the tranny How much is it to change that bearing? Quote Link to comment Share on other sites More sharing options...
SUNNY Z Posted August 23, 2012 Share Posted August 23, 2012 How does one check that output bearing? I have the DS off. It seemed that with the DS installed I could get movement at the tailshaft. When I take the DS off, I can wiggle the output spline easily with two fingers-but I thought that was okay without the DS yoke on there. Like I said though, I can wiggle the DS yoke with the DS in the tranny How much is it to change that bearing? Its a bushing, not a bearing. Sounds like it could have some wear. Bushing is like a $3 part. You will likely have to pull the trans, and take the tail shaft housing to a tranny or machine shop to have it installed. I can't imagine it would be more than $30 to have them do it? IDK, I always do it myself. Quote Link to comment Share on other sites More sharing options...
madkaw Posted August 23, 2012 Author Share Posted August 23, 2012 Looks like I might not have to!!!!!! I just around and no vibration in 3rd during deceleration. Techno version RT mount in and DS angles within 1 degree. Take her out on the highway next!!! Quote Link to comment Share on other sites More sharing options...
SUNNY Z Posted August 24, 2012 Share Posted August 24, 2012 Looks like I might not have to!!!!!! I just around and no vibration in 3rd during deceleration. Techno version RT mount in and DS angles within 1 degree. Take her out on the highway next!!! Boom. And who said you'll never use that geometry class? Quote Link to comment Share on other sites More sharing options...
madkaw Posted August 29, 2012 Author Share Posted August 29, 2012 High speed vibration is still there. Next course if action is: Have all tires balanced again Lower diff pinion another 1/4" to get it dead nuts Wait till this winter and pull engine and trans an have the rear tailshaft bearing checked Have flywheel and PP checked for balance as an assembly Say f$@k it an drive !!!- maybe this will be first Quote Link to comment Share on other sites More sharing options...
madkaw Posted December 14, 2014 Author Share Posted December 14, 2014 Hopefully I have found my issue , but won't know until it's back together. Had the trans rebuilt and the tailshaft bushing was out of round. In his opinion, this was most likely my issue. He also said to make sure I check my pilot bushing. He said the T-5's were notorious for having bad tailshaft bushings. Quote Link to comment Share on other sites More sharing options...
duragg Posted January 8, 2015 Share Posted January 8, 2015 I had to find a shop that could spin the DS to 10,000 rpm to get mine *better*. Quote Link to comment Share on other sites More sharing options...
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