I get some terrible vibrations in my feet and seats when I am doing about 65+. It happens when i let of the gas there is this terrible grinding/vibrating sound and feeling. I don't know what it is all i know is when i let of the gas it just starts grinding. I don't have a front drive shaft in right now. I have an 86 blazer with a 305 and a 700r4 please help me it has started to get worse and it is worse when cruising down the freeway help me before something really goes wrong i don't need any more problems with this thing. "When you say i drive a fullsize are you calling my wife fat." J/K i was bored and made that up i don't even have wife i'am only 17.