Vibration thorugh rear and seat

Hi all,

I'm being stumped about a vibration issue at highway speeds. Happens starting at about 60 and gets worse from there out on out. Ive gone through several sets of tires, driveshafts and balances for both and none of it has fixed anything.

What else could be the cause of highway vibrations?

 

Ujoint operating angles

 

Ill see if i cant take a pic of the angles and post them but they seem to be inline with how a cv driveshaft should be. I had a pretty reputable shop install it but they could of done it wrong. Aside from tires or driveshaft could it be anything else?

 

Frequency on a driveshaft is several times that of a tire vibe. That might help differentiate.

 

I would describe it as a slow vibration that oscillates in and out. Kinda like when you hit the Rumble strips on the road. Its worse on good pavement vs rough.

 

If you have a mechanical fan on the engine,an out of balance blade or a loose fan clutch can make the engine vibrate at various rpms,usually the higher ones..it will also take out the water pump bearings in a relatively short time if driven long enough that way..