vibration cant figure out why

when i put the car into park or neutral and rev the engine there is no vibration. it only starts vibrating when it is driving over 15-20 mph and it seems to vibrate more when it is going up a hill. im pretty sure its not the engine. so does anyone else know what it can be. thanks

Since it vibrates going uphill, It could be due to a driveline out of alignment or unbalanced. I want to say the wheels need balancing, but that would be more pronounced at a higher speed and have nothing to do with the hill. It's a load vibration, so it seems like it's somewhere in the powertrain. Check your motor mounts as well.

when i put the car into park or neutral and rev the engine there is no vibration. it only starts vibrating when it is driving over 15-20 mph and it seems to vibrate more when it is going up a hill. im pretty sure its not the engine. so does anyone else know what it can be. thanks

Hmm.... could be u joint going bad

thanks