Car has a loud vibration when it gets to about 65. I've been told it's wheel bearings & now I've been told it's the differential. Any ideas what it may be?

 

http://www.mazdatrix.com/g2.htm

Bad U-joint or an improperly balanced tire fit.

 

There are a number of things that can cause it but 1 and 2 on the list would be tire balance and probably the u-joints on the driveshaft.

Does this shakes come and go at a lower speed then comes back at 65 but more noticable?
Does the shake slowly come in or is it more like a light switch
Once you pass 65 does it continually get worse or does it slowly go away.
You say you can hear it? Does it sound 'feathery' or 'hearty'
Does the car shake? Steering wheel shake?

 

There's no steering wheel shake. The vibration gets worse the faster you go. It does start becoming worse as you accelerate. It's a very hearty, low frequency vibration. The car doesn't shake either.

 

There's no steering wheel shake. The vibration gets worse the faster you go. It does start becoming worse as you accelerate. It's a very hearty, low frequency vibration. The car doesn't shake either.

 

I have the same problem but its closer to 80mph.... why does everything go to **** in this car above 80mph.... uggg lol

 

Got the same problem and i have lost top end power (does not accelerate that quick as before) and its also eating up gas like no one business. Please help. Does not vibrate on neutral, only 65 and up wtf?

 

A Driveshaft doesn't spin in neutral( while the car is in not moving)