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Discussion Starter #1
I am experiencing a good solid vibration at freeway speeds (more like 75-80mph) and I almost want to call it a shudder because I can feel it in the steering and under neath my seat.

The car is a '91 with only 58k on the clock.

I searched around the forums and took down these notes:

a) No vibration while car is in neutral and speeds >= 80 ---> engine/trans mounts/ harmonic dampener

b) VIBRATION while is in neutral and speeds >=80 ---> driveshaft, gears, rims

c) Rear bearings in the carrier of the differential

d) Tail shaft bushing in T-5 Trans


Now, I was taking a look at my driveshaft and noticed while the pinion flange has a faint yellow mark aligned with the purple dot on the DS, there is also some white paint on the rear u-joint.

Does it look like the driveshaft is installed correctly?

As for my differential, I do have an Auburn unit and it makes some minor noises when backing out of a parking spot for example...isn't this normal for an Auburn?

Thanks in advance!

-Eric


 

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the reverse noise is fine...

you feel in steering wheel... might seem dumb but is tread good all around the front tires? correct wear?

and wobble, loose at all
 

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I personally think its the driveshaft....i dont know exactly what about it could be wrong without being there, but when you describe highspeed vibration its almost always the driveshaft
 

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Discussion Starter #4
I was hoping the FMS driveshaft wouldn't be the culprit...who knows...it could be out of balance, but then I saw the purple and white paint marks, it got me thinking that this DS might not be indexed correctly.
 

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i dunno if this will help but why not trying to get your tires rebalanced. i run into this problem a lot at work as far as a shudder/vibration goes, if that doesnt work...hopefully it will. If not then id suspect that drive shaft. Also check to see if your front bearings are loose, or any looseness in the front end.
 

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I am not sure if I am missing something or misread your post.

Did you just install the Driver Shaft and now your having vibration? Was the drive shaft off then reinstalled?

How long have you had the problem and when did it start? Did you run something over, hit a curb, get new brakes, shocks, anything to do with the rear end.

I have a 2007 Impala that had a vibration that got worse with speed. Ate through tires an alignment check showed the rear tires were like this /\ and the front was just kind of dragging the back around. Came that way from the factory. Just an example. Mine felt like something was out of balance. The steering wheel shook, at 80 my eyes were almost blurry.

Back on topic
If you give a little more info. You listed the things you learned from reading posts, but I did not understand if you have vibration at high speed with clutch in or not.

I have also seen a rim not installed properly where it was hung up a little when the lugs were tightened.

I hope I didnt waste your time.

Aaron
 

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Check for a bent axle also. I took two 1ft sections of 2x4, cut v-notches in them and clamped each axle in there and turned them slowly and checked runout in the middle of the axle with my dial gauge. One had < .010 and the other had .070 :happyhapp Got a good axle from a Mustang salvage yard and no more vibration. You don't have to use a dial gauge, on mine the good one you could barely see the runout and on the bent one the wobble was very obvious.

Messy and tedious job to check, but might be worth it.
 

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Discussion Starter #8
Hey guys,

I am going to re-index my DS and see if that helps.

I did install this item a couple of years ago, but never really drove the car until now. As for new suspension items, the car now has Bilistien struts/shocks, GW rear LCA, stock rear UCA, MM alloy rack bushings, ProCi CC plates, urethane sway bar bushings...the list goes on.

-Eric
 
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