I was running on the interstate....and noticed that after i hit 70mph at...my car starts to vibrate..any ideas on what it can be?

 

alignment

 

Ignore that statement, no alignment will cause a vibration.
You need to first diagnose where the vibration is coming from, the front, rear, or both.
If the vibration is in the steering wheel, then its probably the front wheels, if it feels like its in your seat, then its coming from the rear of the vehicle.
Once you find that out, take it to a good tire shop and have them put the wheels on a balancer to check for a bent wheel, seperated tire, or off balance wheel.

 

really? i've always been told a vibration at high speed is either an unbalanced wheel or you need to get your alignmentchecked. i have a slightly bent wheel and have no vibration up to 130mph

 

Ya, vibration at speed is caused by a wheel being unbalanced.
Alignment problems will cause uneven tire wear.

 

wild *** guess... one of the driveline u-joints is on the way out? you need to add a sig so people don't have to ask what kind of car you have. What car are you talking about?