Bad Vibration @ 80-85 MPH

T-5 Killer · Jan 16, 2012

So I got my car back on the road and it has a very bad vibration @ 80-85 and also on deceleration. It happened with 2 different set of wheels and I just did new U-joints. Its weird because its smooth before that mph.

Any ideas?

det_riot · Jan 16, 2012

Your balancer could be on its way out, check for rubber slipping out around it, Driveshaft could be out of balance. What was your car off the road for?

Slykin · Jan 16, 2012

DOes it happen in 4th or 5th gear, or just one or the other?

2v_takeover · Jan 16, 2012

That happened to me before. My driveshaft was HELLA loose. Needed to snug her back up. Hope that helps.

Musturd · Jan 16, 2012

Drive shaft or balancer I had a bad vibration was from the balancer but I got my frpp drie shaft re balanced as well

ivan12 · Jan 16, 2012

Did you put the driveshaft in the same way you pulled it out?

98rocket · Jan 16, 2012

When i changed my LCA's it threw my pinion angle out and vibrated around that MPH. I got some adjustable UCA's and it cured that vibration right up..

5litrarag · Jan 16, 2012

Check the driveshaft bolts.... does vibe occur only while moving?

Musturd · Jan 16, 2012

98rocket said:
When i changed my LCA's it threw my pinion angle out and vibrated around that MPH. I got some adjustable UCA's and it cured that vibration right up..

Double adjustable uppers FTW

T-5 Killer · Jan 16, 2012

det_riot said:
Your balancer could be on its way out, check for rubber slipping out around it, Driveshaft could be out of balance. What was your car off the road for?

It was down for the winter. I will check my balancer its about 6 years old. Its in both 4th and 5th and only when moving. It seems to be coming from the rear so i wonder if my driveshaft is loose. Like a idiot I didn't mark my driveshaft when I pulled it out so that might be an issue too. Thanks for the info.

det_riot · Jan 16, 2012

T-5 Killer said:
It was down for the winter. I will check my balancer its about 6 years old. Its in both 4th and 5th. It seems to be coming from the rear so i wonder if my driveshaft is loose. Like a idiot I didn't mark my driveshaft when I pulled it out so that might be an issue.

If it's loose then that's probably the issue Check to seee if all the bolts are tight, if they arent tighten them up and try her out. If they are tight, try rotating the driveshaft at different positions!

NJcobra94 · Jan 17, 2012

Could be loose driveshaft, also could be bad rear control arm bushings. When my lowers went had horrible vibration

T-5 Killer · Jan 20, 2012

I checked the Driveshaft and it was tight. I was able to find some faint paint marks both on the pinon and the DS so I lined them up and the vibration is still there. My balancer looks good except I noticed the rubber isn't even so it might be going bad.

98rocket said:
When i changed my LCA's it threw my pinion angle out and vibrated around that MPH. I got some adjustable UCA's and it cured that vibration right up..

Interesting, when the Car was down for the winter I did install lowering springs and LCAs. Any idea what the pinion angle should be @?

Rice_slayer · Jan 22, 2012

When I changed slip yokes on my old car, it started to vibrate the whole car (felt through the pedals mostly) at 130kph+ which is like 80mph. Driveshaft was out of balance as I threw in an aluminum one a few months later, vibration was then gone!

T-5 Killer · Jan 25, 2012

I took it on a drive with the stock rims/tires just to see and I got the same vibration, what was interesting is when I pushed in the clutch and put it in neutral it got A LOT worse. Is that pointing to a trans issue or maybe a bad pliot bearing?

duh09 · Jan 25, 2012

80+mph is over the speed limit so you shouldn't be going that fast ever so just don't go that fast. Ok, problem solved.

I came to say my driveshaft started to come loose once and I had similar issues but it seems you checked that.

Mustang Mark · Jan 25, 2012

T-5 Killer said:
I took it on a drive with the stock rims/tires just to see and I got the same vibration, what was interesting is when I pushed in the clutch and put it in neutral it got A LOT worse. Is that pointing to a trans issue or maybe a bad pliot bearing?

i have the same problem. i really dont think its the trans, pushing in the clutch takes load off of the drive line, so i think it has to do with having play somewhere in the driveline.

5litrarag · Jan 26, 2012

Pushing the clutch made it worse? Did you hold the clutch in? Because if it still vibes with the clutch held in, that pretty much isolates it to in front of the clutch or to the rear end itself because you said it's only while moving. Or maybe the driveshaft really is loose or out of balance. does the vibe increase with speed after 80? And there is no evidence of the vibe before 80? if so it sounds like a harmonic problem, and that would make me look at the DS or the rear end.

302N20 · Jan 26, 2012

T-5 Killer said:
I checked the Driveshaft and it was tight. I was able to find some faint paint marks both on the pinon and the DS so I lined them up and the vibration is still there. My balancer looks good except I noticed the rubber isn't even so it might be going bad.

Interesting, when the Car was down for the winter I did install lowering springs and LCAs. Any idea what the pinion angle should be @?

I assume you have rubber or poly bushing in your control arms, then your Pinion angle should be -2 to -3 degrees with radials/street tires. Check it with with all 4 tires at the same level, i.e. on the ground, on a drive on lift, etc. Here is how to correctly check your pinion angle if you dont' know how to. http://www.wolferacecraft.com/pinionangle.aspx

You want your pinion "nosedown" 2-3 degrees(nose down equals the negative -2 to -3 I ref above) in ref to your driveshaft so when you hit the gas and the front of your pinion gets torqued up it is straight with your driveshaft.

T-5 Killer · Jan 26, 2012

302N20 said:
I assume you have rubber or poly bushing in your control arms, then your Pinion angle should be -2 to -3 degrees with radials/street tires. Check it with with all 4 tires at the same level, i.e. on the ground, on a drive on lift, etc. Here is how to correctly check your pinion angle if you dont' know how to. http://www.wolferacecraft.com/pinionangle.aspx

You want your pinion "nosedown" 2-3 degrees(nose down equals the negative -2 to -3 I ref above) in ref to your driveshaft so when you hit the gas and the front of your pinion gets torqued up it is straight with your driveshaft.

They are poly bushings on both the upper and lower control arms IIRC. Thanks for the info!

5litrarag said:
Pushing the clutch made it worse? Did you hold the clutch in? Because if it still vibes with the clutch held in, that pretty much isolates it to in front of the clutch or to the rear end itself because you said it's only while moving. Or maybe the driveshaft really is loose or out of balance. does the vibe increase with speed after 80? And there is no evidence of the vibe before 80? if so it sounds like a harmonic problem, and that would make me look at the DS or the rear end.

Its not lose I tightened it up and locktited the bolts. The vibration gets worse after 80 I haven't got it beyond 85pmh for fear of breaking something its that bad. No evidence of vibration before that, its pretty smooth. What could cause this in the rear end? Pinion Bearing?