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vibration at 75 MPH

4K views 4 replies 3 participants last post by  punisher69 
#1 ·
2012 srt8 300 with 70k

I would like advice on how to find a 3X tire speed drive line vibration (drive shaft or cv axle)

I have developed a vibration at 75 MPH. The car is not smooth. It is not violent just noticable. I used vibsensor and my phone to measure frequency at 42 hz at 70 and 45 hz at 75. This corresponds to 3X tire rotations.

45 HZ X 60 secs/min X 60 mph / 75 mph / 724 rev per mile (nitto motivo) = 2.98

I originally used 704 revs per mile and got 3.06 which caused me to think driveshaft. I inspected the flex discs and there is no visible cracking (other than what looked like paint and wiped off) and the center bearing appeared tight (no movement). There was very slight movement in the slip part of the shaft.

I looked up the manufacturers revs per mile and got a a ratio closer to 3.0. Does the CV axle shaft have tripots that cause third order vibrations?

What all parts can cause this and what diagnosis methods should be used to identify the marginal parts?

Thanks

John
 
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#2 ·
Does the vibration go away at higher or lower speeds?

Honestly sounds like a tire balance issue. Even good balancers leave a little buzz area, usually a 3-5mph range somewhere between 65-80mph. Anything outside of that little 3-5mph spot, you won't feel it at all.

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#3 ·
^^ same here.
 
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