# 60 mph vibration



## rod collins (Jan 12, 2008)

When I go over 60 mph I get a noisy vibration. I have new tires and wheels, also a new driveline. Up to 60 car runs very smooth. Anybody have any suggestions?


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## dimitri (Feb 13, 2009)

The new wheels/tires could have thrown a wieght. Have the tires rebalanced.


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## geeteeohguy (Feb 2, 2008)

How long have you had the car? Did it vibrate before the new tires/wheels? Or did it just start to vibrate? Need more info in order to help you.


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## BearGFR (Aug 25, 2008)

rod collins said:


> When I go over 60 mph I get a noisy vibration. I have new tires and wheels, also a new driveline. Up to 60 car runs very smooth. Anybody have any suggestions?


Always suspect the last thing you changed, or something closely related to it, especially if the problem didn't exist before the change. Does "new driveline" mean new driveshaft? Suspect its balance and/or its alignment/straightness - try running the old driveshaft if you still have it and see if the problem goes away or changes significantly. Another thing that will cause a vibration like that is the pinion angle being "off" - as in the centerline through the axis of the pinion gear in the rear-end not being exactly parallel with the centerline of the crankshaft. Have you changed engine mounts? Transmission mounts? anything that might have changed one or the other of those two angles?

Bear


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## rod collins (Jan 12, 2008)

I did install a tremec 5 speed. So maybe the pinion angle is off. I will check the angles before I do anything else. Thanks for the help.


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## BearGFR (Aug 25, 2008)

rod collins said:


> I did install a tremec 5 speed. So maybe the pinion angle is off. I will check the angles before I do anything else. Thanks for the help.


Aha! If mounting that Tremec "tilted" things, changing the output shaft/crank angle, and if you're still using the stock upper/lower control arms on the rear, I'll bet you a buck against the hole of a rolling donut that's your problem. You options would be to restore the crank/output shaft to its original angle by raising or lowering the tranny tail shaft, or to change to a set of adjustable upper control arms on the rear. Dunno what you're goals are for the car or your budget, but going with a set of adjustable uppers like these that have the fully articulated joints on the chassis end has another benefit: they don't bind like the factory ones do. The geometry of the triangulated rear control arms is such that as the rear end moves through its range of motion, going up and down and ESPECIALLY when rolling in a cornering situation, the upper control arms must twist on their bushings. Putting aftermarket polyurethane bushings at these points actually makes the problem worse because they're harder to deform, and that prevents the axle from being able to freely move throughout the full range of motion. Personally, I like Spohn because of their quality and price, but there are many sources for upper arms with front joints that don't bind.

Bear


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## ALKYGTO (Mar 29, 2010)

I had to shorten my driveshaft when I installed my Tremec. 

If you did'nt do that it could be in a bind. If you did shorten it, was it "phased" correctly? The original orientation of the yokes must be maintained or it will create an imbalance.


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## BearGFR (Aug 25, 2008)

rod collins said:


> I did install a tremec 5 speed. So maybe the pinion angle is off. I will check the angles before I do anything else. Thanks for the help.


Here's a link with some pictures that describes the procedure, shows a tool that can be used, and also explains what causes the vibration. There are many sources for this information, and some of the procedures are different. They're all shooting for the same goal of making the centerlines of the pinion and the transmission/crank parallell with each other.

Bear


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## rod collins (Jan 12, 2008)

I finally got to setting my pinion angle. That seemed to fix the problem. I do have the adjustable upper control arms which made the job easier.


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## BearGFR (Aug 25, 2008)

rod collins said:


> I finally got to setting my pinion angle. That seemed to fix the problem. I do have the adjustable upper control arms which made the job easier.


Bingo! arty:

Glad that you were able to get it corrected.

Bear


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## geeteeohguy (Feb 2, 2008)

Yes, me too, and thanks for letting us know the outcome and cause of the problem!


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