harmonic vibration

[burt ragio]

I'am calling it a harmonic vibration (hv). I felt this since the 1st day I bought the car off the lot new . At around 60 mph the (hv) starts. I racked this up as wheels needed to be re balanced. I had them balanced three times. The last time with a road force machine. Since I have had my gears changed to 4:10s and loveing them now, that things are spinning faster (hv) is now more pronounced. I can't pin point were it is comeing from. My guess is it is the drive shaft. I have checked the trans tail shaft bearing by visual and shakeing the yoke seems fine checked drive shaft u-joints they seen fine. This leads me to believe the (hv) is comeing from the drive shaft. Has anyone else had this problem ? Should I get the oem shaft balanced is it cost effective or should I buy a special drive shaft instead ? Open for suguestions.

[Richy04]

Most GM cars had a balance of the shaft that yielded a slight shimmy of the drive shaft at around 65 mph, it went away above and below that.

I never really noticed that on Fords though but my guess is their shafts may have had a static balance where somewhere around 70 it happens and now that you went to 4:10's its now lower and more noticable at legal speeds since the shaft is now spinning faster.

Just about every car I owned with a driveshaft had it somewhere between 60-80mph so if its not too noticable and the weights are present on the shaft and it doesnt look damaged, you can have it balanced but it will just move the vibration around, but it wont eliminate it.

[fastblackmerc]

Do you feel it in the seat or the steering wheel?

[Bradley G]

I had that. several others have too. Mostly tires, were the culprit. Once I read a guy had his wheels causing this.
I'am calling it a harmonic vibration (hv). I felt this since the 1st day I bought the car off the lot new . At around 60 mph the (hv) starts. I racked this up as wheels needed to be re balanced. I had them balanced three times. The last time with a road force machine. Since I have had my gears changed to 4:10s and loveing them now, that things are spinning faster (hv) is now more pronounced. I can't pin point were it is comeing from. My guess is it is the drive shaft. I have checked the trans tail shaft bearing by visual and shakeing the yoke seems fine checked drive shaft u-joints they seen fine. This leads me to believe the (hv) is comeing from the drive shaft. Has anyone else had this problem ? Should I get the oem shaft balanced is it cost effective or should I buy a special drive shaft instead ? Open for suguestions.

[Marauderjack]

Try removing the shaft at the pinion flange and rotate it 180* and bolt it back.....may just fix it for you??:cool:

[Haggis]

Have your tires road force balanced and see if that helps.

[burt ragio]

Do you feel it in the seat or the steering wheel?
In the cabin and just enough to be annnoying.

[burt ragio]

Try removing the shaft at the pinion flange and rotate it 180* and bolt it back.....may just fix it for you??:cool:
I will give it a try and let you know what happens.Thanks

[gohogs]

You might want to review this old thread:

http://www.mercurymarauder.net/forums/showthread.php?t=22666

[Stranger in the Black Sedan]

Mine does it too. It is barely noticeable, but on a long trip I do notice it. I flipped the driveshaft 180 and it slightly reduced the vibe but I can still notice it. It is most likely driveshaft. Because these cars are so humongous and have the longest driveshafts known to man, any imbalance is really going to show up.

Have a shop check the shaft for straightness and rebalance if necessary.

[Aren Jay]

You could just replace the drive shaft with the high speed one and fix both problems.

[Stranger in the Black Sedan]

BUT people who use the super expensive lightweight shaft often complain that it transmits more gear noise (there will always be SOME gear noise, gears operating can never be perfectly silent) to the cabin. Since I don't plan on extended 125+ driving, the trade off of more gear noise is not acceptable to me. I'll take my chances w the stock shaft, rebalanced.