# vibration



## maktope (May 22, 2013)

Awhile back i put in a rebuilt 12 bolt rear end, still had wheel hop so i installed lakewood traction/lift bars. Everything was going good. Then i jump on the freeway. At 50 mph i get a slight vibration, that increases with speed. At 70 its almost undrivable. Since then i have had the pinion angle checked i was at -2degrees, now i am at 0. Drive shaft checks out ok. Next step is to remove the traction bars. Could the bars be the cause of all that vibration, if so i cannot see why. Any info or ideas will help i am at a loss.


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## geeteeohguy (Feb 2, 2008)

You need some drive shaft angle. 2 degrees is about right, either way. What changed? Did it vibrate before the no hop bars? The rear end could be out of alignment, the driveshaft could be bent, the u-joints could be out of phase or off center, and on and on. When did the vibration start? There is a _very_ good thread on driveshaft angles on the Performance Years forum.


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## ALKYGTO (Mar 29, 2010)

Agreed ^ need to add some angularity to the driveline, trans, driveshaft and rear cannot be perfectly in line or you will get vibration. Adjustable upper control arms would solve this.


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## BearGFR (Aug 25, 2008)

:agree The drive-line angle at the rear end has to be the same as the drive-line angle at the transmission, or you'll get vibration. 

Check out this link:

DRIVE LINE PHASING

And Alky's right - the best way to adjust is to use a set of adjustable upper rear control arms.

Bear


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## 05GTO (Oct 6, 2004)

In addition to the great advise above check the length of your drive shaft, I have a 12 bolt in my 67 and was also having vibration problems. I had my drive shaft shortened a couple inches and that resolved the problem.


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## maktope (May 22, 2013)

Had shaft rebalanced, pulled the whole rear off, inspected all bushings mounts and ect. reinstalled everything went -2 pinion angle then + 2 vibration at +2 started at 45. But what i have noticed on smooth ground the vibration is there through out, ironically it doesnt seem to get worse or better with RPM just speed. I am at a loss, think its time to take it too a shop.


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## BearGFR (Aug 25, 2008)

What does the angle measure at the transmission end?

Bear


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## maktope (May 22, 2013)

about 8.5


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## BearGFR (Aug 25, 2008)

maktope said:


> about 8.5


Then set the angle at the rear axle to the same 8.5. What you're trying to acheive is getting the centerline of the pinion gear parallel to the centerline of the transmission. 

Like this:

transmission -> -------------

---------------- <= pinion

But not like this:

transmission => ---------- ---------- <= pinion


Make sense?

Bear


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## Rukee (Feb 8, 2007)

What rims do you have??
Reason I ask is I was chasing a vibration and it ended up being my uni-lug rims. Had a set of rings made that go over the hub and fit inside the rims that perfectly center the rims and vibration disappeared.
Have you had the tires balanced? Maybe a belt coming apart in one of the tires?


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## maktope (May 22, 2013)

I have american racing AR series. i was lucky enough to have a day off here, and was able to get back under the car. Hopefully problem solved, the weights came off the drive shaft. I am going to pull it out on thursday and drop it off to be balanced again. hopefully that will solve this. And thank you guys for the time


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## maktope (May 22, 2013)

Ok finally problem solved, bad spider bearing, was slipping a lil bit thus causing driveshaft to be off balanced, installed new one today and its driving great. And it wasnt a light bulb going off to tell me to check it. I was pulling the driveshaft and it fell off. but ill take it.


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## Instg8ter (Sep 28, 2010)

Good deal, often its the simplest things, thats why when trouble shooting you start with them and eliminate whats right until you find whats wrong.


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