i spoze if i had time i could link you to a 10 TEN page post i think started by doc68 trying to find a vibration that is like every second at certain rpms regardless of what gear he was in. i got the same problem. the thread was closed by moderators cause it reached ten pages. causes mentioned by the board were flywheel, t converter, driveline angle, driveline, rear trans bushings and u joints. i have the same problem. and he never got it fixed or figured out. ITS HERE: http://www.hotrodders.com/t47958.html
last night a trans guy says it's not my trans. i didnt have this vibe till i put in a th400 in place of my th350 tho. he said unbolt the converter and rotate it to the next hole then the next and see if it goes away. i have already changed both u joints. the driveline guy says it wouldnt be the driveline so... guess i'll try it. the motor guy says my motor has a strange vibration as well. the tranny guy also says to unbolt the converter, push it back, and see if the engine's vibration goes away. i guess i am going to try that.
another friend mr goodwrench says i could try and chase this vibe down for ever and not find it. anybody think this torq converter rotation might fix anything? this is free at least, i am gonna try it and then take the driveline in anyway. there is no slop in my trans bearing, everything is tight there. bye