Vibration at 65+ mph

[87gninpa]

Having a vibration problem on the highway. Car is extremely smooth from 0-65 mph, then all of the sudden at 65 it starts vibrating. Its a very tight vibration (if that makes sense), and coming from under the car almost, feels like the rear of the car. Here is what I have done so far: Balanced all four tires, verified the converter is locking, checked the rear gear oil, tranny fluid, and both U-joints. All seem just fine. If anyone has had a similar problem, I would grealty appreciate the advice. btw, is only happens with speed, if I rev it in park or am in a lower gear at the same rpm, no vibration.

 

[DailyDrifter]

possibly driveshaft

 

[BlackBandit]

How did you check your u-joints? If this is something that's developed that's where I would look. If you've had your driveshaft down I would try unhooking it from the rear yoke, spinning it 180 degrees, and hooking it back up.

 

[DR BOOST]

check your pinion angle

 

[turbocam]

check your converter bolts

 

[mybuick]

i bought new tires and vibration gone

 

[Roc87]

Rear end bearings? Pinion bearing?

 

[mybuick]

bearings will make noise and vibrate all the time. and louder the faster you go

 

[Pronto]

Get your driveshaft rebalanced, not real expensive.

 

[87gninpa]

Thanks for the replies guys. Here are some answers: I have never had the DS down, have only had the car for a week or two and has done it since I got it, so it is not something that has developed. I have the car on a lift at work today and was looking around and the driveshaft moves about 1/8 of an inch up and down where it goes into the tranny. Is it supposed to do that? I will also check the converter bolts. Is there a way to check the rear end/pinion bearings? Lastly, I want to stress that this only happens above 65 on the highway, there is absolutely no vibration or anything under that speed at any rpm. Only mentioning that again because I dont want to go nuts looking for problems that wouldnt be present under this consition. Thanks

 

[usetaboost]

Is the vibration in the seat or steering wheel? If it's in the seat I would start with looking at u joints, pull the tires off and YOU watch the tires turning on the balancer and how much weight they take. I'd take it to another tire shop and get a second opinion. Jack the back of the car up and let them roll in drive (with an assistant of course ) and check for bent axles. Motor mounts, tranny mounts, bad rear suspension, most likely not but it's possible.

 

[86GN-862+2]

If I was guessing, I would say it's in the driveshaft. I bet the yoke has play at the transmission output shaft. Plain wear and tear. I had this happen on a 1987 Monte SS too.

 

[Rodney87GN]

verified the converter is locking

Try unlocking the converter at 65mph and see if it still vibrates by tapping the brakes with your left foot and maintaining speed with the other. If it still does it then you have a bad converter. I found a bad converter on my Tahoe by doing this. It's actually quite common on a 4L60E tranny. It was doing the same vibrations as you described on your GN.

Also jack the rear of the car and place it on jackstands. Put the car in drive and watch the driveshaft to see if it's actually spinning straight. I found a slightly bent driveshaft in my IROC doing this...no amount of balancing will ever fix that.

Anyways just throwing those out there before you plop some money into troubleshooting your problems.

 

[vacuum 6]

i bought new tires and vibration gone

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