JR HAWK 9

iTrader: (3)

OK, I am trying to get down to the bottom of my high speed vibration that I have had for 3+ years and I -think- I almost have it licked. I thought it was my rims and tires but when I got a new set of rims/tires, the vibration remained exactly the same so I figured it wasn't it. I then replaced my TA with an adjustable one and set my angles correctly (was off 3+ degrees), that eliminated A LOT of it, but I still had some. I then bought an adjustable panhard bar to center my rear end and also had my u-joints replaced (with greaseables ) and my stock driveshaft balanced. The guy that balanced my DS said that he had to straighten it first a little bit because the runout was out of spec. He then balanced it but his machine (some old thing) only spins at 2,000 rpm's. After he straightened it and put the new u-joints in he put it on the balancer and told me it didn't need any weight and that it was off only 1/10 inch ounce (?). He told me I would -never- feel it and that his machine is more sensitive that my car is. He deals with mainly heavy duty trucks and such. I have all poly suspension bushings as well as a double rod ended panhard bar therefore my suspension will tend to transfer driveline vibrations just a -tad- bit more than a dump truck would....lol Well, I take the shaft home and install it. Take it for a ride and it vibrates noticeably WORSE than it did previously. I then drive it back home and unbolt the shaft from the pinion yoke and rotate it 180 and bolt it back up. Take it for another ride and it is much better. I still do have a VERY tight vibration at highway speeds though but it is better than it was before I had it straightened and balanced. The vibration I have now seems to be even tighter than what I had before the balance and new u joints and seems to get tighter with increased speed. At 115mph it gets to be pretty noticeable.

Could the shaft -still- be out of balance?? How much difference does a 6, 7, 8, 9 or 10,000 rpm balance make compared to only a 2,000 rpm balance? The guy that did mine seems VERY knowledgeable, but he seems to do mainly heavy equipment shafts and hardly any sports cars. He told me that he hardly ever does an aluminum shaft and that he has to switch all his stuff over from steel in order to weld on them.

I am now thinking of taking the plunge to a carbon fiber shaft, as they are supposed to be the -best- for reducing drivetrain related vibrations. I don't drag race the car nor do I consider myself hard on the drive train (never have even done a single clutch dump or burnout), therefore my main purpose of swapping driveshafts would be to have a -very- well balanced shaft capable of spinning 7,000 - 8,000 rpm's safely and w/o vibration. I drive the car only on nice weekends and like to take small road trips with it and sometimes end up doing 90-120mph when the highway opens up enough to safely do so.

anybody have any comments or suggestions on if they think a carbon fiber driveshaft could possibly take care of my vibration...?

thanks for any help..
Paul

todddchi

iTrader: (3)

I dont' want to be dumb here, but from the sound of your story was the stock driveshaft balanced including the pinion yoke and the transmission yoke?

It needs to be.

JR HAWK 9

iTrader: (3)

no, it wasn't done with the pinion yoke but WAS done with the tranny yoke. When you buy a brand new driveshaft they obviously don't have your pinion yoke to include it with the balance of the new shaft.

todddchi

iTrader: (3)

Well it needs to be balanced as an assembly. I wouldn't spend another dime until you do that.

Obviously, you can do what you want, though.

2001z

iTrader: (32)

I dont think having the pinion yoke will make a diffrence like you have stated when you buy a balance driveshaft they dont have your pionion yoke on hand. I would ask someone you know that has an LS1 to let you try there drivshaft real quick since changing drivshafts is pretty easy. If another driveshaft doesnt help look at the wheel hubs . I know a worn or wrong trans mount will do the same thing also.

MeentSS02

iTrader: (11)

Trying someone else's driveshaft would be the easy fix - hell, if you were close enough, I'd let you try my carbon fiber one. It could be a messed up pinion angle too, but who knows.

JR HAWK 9

iTrader: (3)

yeah, I am thinking about checking my trans mount. I am not hard on my drive train at all though, so I don't know how the tranny mount would be bad at 57,000 miles.

Steve, I have my pinion angle (in reference to my tranny output shaft) as close as I can get it with the analog angle gauge I have. It was off by roughly 3*, but now it's within a 0.5*

I think I might take the plunge on a CF shaft. I have called and taled to a few companies and looks like I might be going with PST. I called ACPT and the guy I talked to couldn't really answer my questions and found out they only have a year warrantee. PST told me that stand behind their product 100%.

MeentSS02

iTrader: (11)

Yeah...the guys at PST impressed the hell out of me when I talked to them when I was ordering mine.

As for the transmission mount, mine was tearing after about 35k miles or so on mine. I'm a bit harder on my car than you from the sounds of it, but still...kinda shitty. I have poly motor mounts along with the poly trans mount, and haven't looked back since.

todddchi

iTrader: (3)

I don't see how you can possibly continue to ignore the pinion yoke influence when you acknowledge in your original post that flipping it 180 deg made a difference.

Just trying to save you some money.

JR HAWK 9

iTrader: (3)

I do see what you are saying, but I flipped the whole driveshaft/tranny yoke 180*...not just the pinion yoke.

BTW, where can you even get a new Saginaw S44 or 3R pinion yoke?? All I can find are the 1310/30/50 pinion yokes. I suppose I could buy a new 1310 pinion yoke so I wouldn't have to use a 1310/S44 conversion u joint with a new 1310 series shaft.