Is this a big deal? I rushed my clutch job and forgot to check the mark I made when took everything apart,the car has developed a very focussed vibration that starts right at 3000 rpm in fifth gear.Its a smooth as silk up till then I think the energy mount is partially to blame I never put the shim in like the instructions say to,I hate to put the stock trans mount back in I like the way the poly mount feels.If the driveshaft is reassembled 180 degrees out of phase can this cause a serious problem?The stock driveshaft was professionally balanced and the ujoints are in good shape.Any feedback would be greatly appreciated,thx