Driveline Roughness

[Larry Gillam <mit-eddie!hpfcpe.fc.hp.com!gillam@EDDIE.MIT.EDU>]

        My '72 TR6 starts to show an annoying roughness when the drive 
        line is "unloaded"(the point at which you're neither accelerating or 
        decelerating)at around 65 mph. The roughness is there at all
        speeds above 65, but worse when the driveline is unloaded. All 
        the U-joints in the rear have been replaced and I plan to replace
        the two drive shaft joints soon. My question comes after reading 
        the drive shaft section in the Haynes manual. It talks about 
        marking the U-joint flanges so as not to disturb the "carefully 
        balanced" drive shaft. Is this to be believed? If this IS critical 
        how do I know some previous owner hasn't unknowingly installed it 
        improperly. What is the proper way of removing and replacing the
        drive shaft?


                                                Thanks.....Larry