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View Full Version : Help!!! slight drive line vibration driving me crazy



66ls2
06-16-2011, 05:29 AM
I have 2 separate issues or maybe they are one ? I start to pick up a slight vibration at 64 mph and up or at at about 3500 rpm @ 1to1. I also have a shutter occasionaly when starting in first gear or reverse depending on how I let out the clutch. The car is a 66 chevelle convertible with an LS2, new stage 2 monster clutch and flywheel ,tremec 5 speed with manual clutch linkage, new driveshaft,new moser 12 bolt ,adjustable curry trac rear arms. It is not possible to get my driveshaft working angles correct becouse of the car being lowered and the transmission downward angle. I have adjusted the working angles in all different configurations and this setup is the lowest amount of vibration : Transmission 5 deg. down ,drive shaft 1 deg. down, pinion 2 deg down. The car has under gone several different setups over the last couple of years different motor and clutch, stock driveshaft vs. new and the problem has always been there I have had all the wheels balanced twice. I am pretty sure it is the driveline working angles that are the issue and did not know if there is anything else I can do to correct? The one thing I did notice is that when I went from my stock shortened driveshaft to a new thicker/heavier custom drive shaft the vibration seamed to be a little worse I am thinking the additional weight enhances the incorrect working angles would a lighter alum. driveshaft help? Any help would be greatly appreciated this problem is making me crazy.

Z06vet
06-16-2011, 06:24 PM
It seems you should have the pinion angle up, not down. If the trans is down 5, and shaft is down 1, pinion should be up. I am dealing with the same issues with a lowered car. I can't get much more than 0 degrees on my pinion, maybe +.5 is all. The threads on the upper bar ends are more than half way threaded out at 0. I am going to try some longer threaded ends or longer upper bars. Do you have any room to raise the trans tailshaft? I was able to gain a bit by shimming the trans mount. I have a camaro though. This is a good article thats easy reading. Scott
http://www.hurst-drivelines.com/files/Universal_Joint_Alignment_Proc_111606.pdf

66ls2
06-17-2011, 06:29 AM
Thanks I have previously read that article and have tried to put the pinion up and have the same problem I as you I start to run out of thread. Believe it or not I got the pinion to 2 deg up and driveshaft 1 deg up and the vibration was worse I think it is becouse I could not get to the sweet spot to cancel out the working angles and with the transmission down 5 deg and shaft up 1 deg it increased the front u joint to 6 deg . I have raised the transmission as much as possible the knuckes on the u joint are 1/4 from the driveshaft tunnel . The BRP engine mounts I used put the engine up so high that you end up at a 5 deg trans angle if i did it again i would have used different mounts but there would have been other tradeoffs. If i could find longer turnbuckles for the upper control arms i could put the rear up 5 deg then it would be parrallel with the transmission.

66ls2
06-17-2011, 06:49 AM
Anybody know where I could source longer alum. couplers I believe the thread is 7/8" or 1"?

nicks67camaro
06-17-2011, 08:42 AM
I had a bad vibration after an t56 swap I did in my 67. I checked everything.....drive line angle, drive shaft, wheels, everything. I was using solid body mounts, with an 8pt cage, and a brand new performance trans mount. for some reason all that acted like a big tuning fork and once i swapped out the hard trans mount for a "stock replacement" my vibration went away. Not even a hint in the shifter. Its a pain but you'll get it. good luck.

Z06vet
06-17-2011, 06:21 PM
I have solid body mounts but stock rubber T56 trans mount. One of the suspesnion vendors should be able to get us some longer threaded adjusters for the bars. I know Frank at prodigy can get them but I have not been able to get a hold of him.

JEFFTATE
06-17-2011, 06:23 PM
It's hard to get the working angle correct with the car lowered .
The rearend is just too far up in the car to get it exactly right..
Andrew Borodin and I have had several conversations about this problem.
I have it on my '69 Camaro , he has it on his GTO .
His current idea is a custom driveshaft made of either aluminum or carbon fiber with a CV joint at the front , because CV joints will work at any angle and not induce vibration ..
He's gonna try it first and I will probably follow suit ..

Rubber mounts will help isolate the vibration , but the CV joint will help eliminate the source vibration .
And a different driveshaft material (other than steel ) will transmit less of it into the transmission.

Z06vet
06-17-2011, 06:31 PM
I read a thread about that recently- i think it was his with the GTO. A guy I met on the powetour a couple weeks ago has an LS1 chevelle and also had a slight vibration. He used the CV joint you described and he said its all but gone. Every now & then he would feel just a hint of vibration but it comes & goes quickly. Must be that it finds a certain speed & load every now & then for a split second. I am curious to see how this turns out for Andrew.

66ls2
07-25-2011, 04:15 PM
Problem solved. I brought the car down to Mitchels Drive Train in MA to have a look becouse I was stumped they checked my driveline angles and said they were acceptable re balanced the drive shaft which was perfect and the checked the tranny. Everthing checked out then they ran it on the lift and could see the rearend and driveshaft moving around when it got up to speed so the pulled the wheels and turns out both rear axles are way out of tolerance on the face where the wheels bolt on the passenger side was not as bad as the drivers side. They pulled both axles and replaced them and the car is smooth now 90% better there is still a little vibration in the shifter handle but it is consistant from 40 mph up to 100mph I may be just getting to fussy so I am just going to run it feels like it is in the tranny becouse you feel it in the shifter and clutch pedal. I am also very particular about rattles ,vibrations and such but at this point I could chase forever. I never considered the rearend becouse I bought it new and have only put 4000 miles on it. But after thinking about it the problem was always there and I thought I had a bad wheel and replaced, driveshaft replaced just never thought about the axles so much for new product and know it was not a cheap rearend it was a brand new Moser and what a POS I changed the gears last year becouse they whined so bad now bad axles at least the problem is solved and if you ever need a good driveline shop in massachusetts look up Mitchel drive train/Mitchel differential great bunch of people that where really willing to help the actually cared and gave great service unlike when you call the big companies that are just selling parts and could give a you know what.

Z06vet
07-25-2011, 04:25 PM
Well I am just about to get the gears changed in my moser 12 bolt as well. They wanted me to ship the entire rear end back to them. We agreed on them sending me new gears & install kit. I will check my axles play as well. I am having the tech document the existing gear setup and use marking compound to see if it it was set up right. If I had to do it over again I'd probably get an 8.5 10 bolt or build a 12 bolt. It would have been much cheaper in the long run. Still have the issue needing linger adjusters to get the right pinion engle, but one thing at a time. I too have just the slightest vibration in the shifter at variong rpm ranges and loads. I just cant stand the gear whine any longer, its awful.

66ls2
07-26-2011, 01:42 PM
good move I could not live with the whine any longer and changed gears last fall best thing I ever did. Unfortunatly I had to by the gears myself but still money well spent. So you do the math new rearend from Moser set up + $250.00 for gears & install kit + $800.00 for new axles installed + my labor to change the gears + aggravation and time to diagnose. mmmm I got screwed next time I will have this shop that repaired the axles build me a rearend. I have not told you the best part that is the second rearend from moser the first one they sent me (that was all installed in the car and I had to remove and send back to them) was short one one of the axle tubes and when I went to install the disc brakes the axle was sticking out an extra 1/2" and I could not put the disc brakes on.