95 GT problem

hey guys i have a question for anyone who can answer it.

My brother is trading his 96 talon tsi awd for a 95 GT its all stock except for a K&N drop in. I have a question though in regards to whats wrong with the car, i just took a look at it tonight with him.
The guy thats trading said that when ur driving along at about 55 the car starts to shake, he said it happens around 80 too when you let off the gas. What could this be. There is a steering fluid leak too. I'm not sure where its coming from though, it was dark out by the time we got there. Could it be the steering that making the car shake, or could it be that the car threw a weight on one of the wheels?? Possibly a wheel bearing?? any thoughts would be greatly appreciated. Thanks guys!!!

im not sure about at which rpms it does it at, im assuming it does it at different rpms, its an auto. although the harmonic balancer would create a vibration right?? im not sure what it would feel like. but that could cause things to start failing as far as i know, for instance the p.s pump which the guy said it had a leak, but there was no fluid under the car. maybe its the balancer and the p.s. pump is on its way out the door... although i will definatly check the drive shaft bolts, thanks for the heads up guys!