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sabre81
08-06-2002, 11:00 PM
little vibration at about 50 mph and up. It seems to vibrate more when im crusing at about 65-70 and let off the gas a bit right at about the point where the boost gauge reads around 20 in vac

any ideas? thanks

Mike8675309
08-07-2002, 11:29 AM
I would start by swapping wheels front to back to see if the vibration follows the swap.

If so, it's either a problem with a tire or a wheel.

Deep6
08-07-2002, 08:33 PM
I got my new ALuminum drive shaft and I still had a persistant vibration around 70+miles an hour.

The vibration is in the seat of the pants and a little through the steering wheel (you can actually see my hands shaking).

It mostly occurs during cruise and running up to about 5" of Vac, but letting off the gas back down to 20" of vac and the vibes will subside.

I know that I have crappy pep boys tires that will be 3 years old this september. I had them Hunter force dynamically balanced. I even alinged the valve stem to the painted lug up front (which did help a little bit). But there is no painted lug in the rear.

Still though I have the vibe a little bit. Other than getting new tires, and a alingment, I don't know what it could be.

Mike8675309
08-07-2002, 08:52 PM
If the vibration changes based on throttle position, it is almost always going to be somewhere in the driveline.

I'd say CV-Joints in the rear axles. Which one? Don't know, but look for a torn boot letting contamination in.

If the CV-Joint wears, it starts to get more and more loose in it's coupling. A loose joint will walk under power as it winds up, and under deceleration as it unwinds. But at cruise it just idles and is less likely to throw off balance.

They should be possible to check on a lift. I'm just not certain of the best way to check them.

They should be pretty solid if you grab them and move them. Or lift the car and spin the wheel listening for any odd sound.

Yes I'm guessing but to be impacted by you adjusting load on the driveline really makes it something in the driveline.

(Could even be the yokes or flanges that the driveshaft bolts to that might be worn and causing the vibration.)

Deep6
08-07-2002, 09:18 PM
I know my halfshafts and CVs are allright. There isn't any clicking they are tight in there and none of the boots are torn and leaking.

So I don't think those are worn. I know that the drive shaft came with it's own yokes welded to it and had new spicer U-joints.

It was high speed balanced too.

I'd like to figure it out on my own without having to take it to a dealership.....

Mike8675309
08-08-2002, 12:07 PM
One other thought would be exhuast. Exhaust systems can sometimes be the cause of vibration issues with cars and especially semi-trucks. Then tend to pulse and can create a resonance with other items in the vehicle that can create the appearance of a vibration.

You might inspect the hangers for the exhaust and the pipes to make sure nothing is touching and the the hangers are properly isolated.

Deep6
08-09-2002, 10:25 PM
I've looked under there and that didn't look out of place either. I seriously think that it is due to bad tires though. Could this prob be bad tires? Or what about "out of round" wheel bearings???

Mike8675309
08-10-2002, 08:36 PM
"Out of Round" wheel bearings would be extremely noticable and would vibrate at all speeds.

Of course out of round bearings would be the bores for the bearings are likely shot as well. This not a likely cause.

Bad tires are a #1 cause of vibrations. Radial tires are made up of belts. A bad tire, or an old tire, or a tire that's been overheated can have belts that start to move in the casing. Not only can this cause balance issues, but it can cause catastrophic failure of the tire.

Note that you should pick this up on a spin balancer that spins the tire at a high rate. Not all of them do. It's noticed by the tire computer having trouble locating the point that needs the weight. The spot will often keep moving.

Deep6
08-10-2002, 09:50 PM
When he was down at carlisle 2002 he and I drove rode in my car and he speculated that it was a bad belt in one of my tires.

Since I'm due for a tire change soon, I'll report back if the vibe went away.

I'm also considering upping my rims to 17" tires could this excaserbate the vibes if in fact the cause was something else?

Mike8675309
08-11-2002, 01:13 AM
No. If the vibration is related to your tires or wheels now, new tires and wheels would take care of the issue.

If the vibration is related to your axle shafts or bearings. Well, they'll still be there, thus the problem should still be there.