i have an 84 5.0 with a t5 trans. The other day the car starting vibrating bad over 3000rpms it happens in every gear. i checks the u joints they seem solid. when it shakes it just isnt the shifter its the floorboards the seats everything. my h pipe is loose but i didnt think it would be that because if the car is sitting in nuetral or with the clutch in in 1st and i rev it up it dosent do it. the rear has some backlash in it but not much. I was wondering if anyone had any ideas of wat it could be. Im going to check the car out tommorow so if anyone has any ideas of wat i should look for id appretiate it.