We have a big driveshaft shop in nashville thats been around for YEARS and they are the ones that cut down the driveshaft and installed the u-joints and balanced it.. They are well known and used by lots of people so i just assumed it was done right, but i dont know..Why do most NOT high speed balance the shafts being that they DO indeed spin quite fast? Seems as though there is a lot of vibrations running around if thats the case..My next question is, could it still be a problem in the transmission and it doesnt show untill the driveshaft is installed?