i am trying to replace my drive shaft tail seal and i was wondering what are the proper steps.

now i was told that i need to make a straight line down the driveshaft with soap scum b/c the drive shaft could become out of balance when i put it back in. is this true? thanks

Is this a power glide,350,400 or manual? The first thing I would do is block the front wheels and jack the back of the car up. This will help stop any fluid from coming out the back. Unbolt the rear straps and remove drive shaft. Theres a couple of ways of getting the seal out. Hammer and screwdriver or a tool used for pulling seals. I have never heard of the drive shaft getting out of balance. On newer cars when pulling 4 wheel drive shafts out I like to put them back in the same position. If this is a turbo 400 and the seal is leaking more than likely the bushing that the tail shaft rides on is wore out to. At this point you will need to pull the rear housing off and have a new bushing installed.

I think he means he is marking the orientation of the u-joints. Putting them back in the same position they came out will keep them in "phase" and eliminate the possibility of vibration.

The parts wear into the mating parts, so yes mark it all and put it back the same, as Jeff said.

i have the turbo glide 400, and thanks for the info i will use it

I'm not positive on the th400, but most automatic output shafts have a "blind spline", meaning 2 splines joined together at the end.
If you look at the female splines of the transmission slip yoke, you may see what appears to me a missing tooth. This would line up with the blind spine of the transmission output shaft.

This is the method used for ensuring the driveshaft goes on the same way, or as Jeff says "in-phase".

Trevor

The only way the u-joints could get "out of phase" would be if the drive shaft was cut for some reason (shortened or lengthened) in which case keeping the joints exactly as they were installed is very important. Since both u-joints are welded to the drive-shaft they can't move so you don't have to worry about them. Every yoke I've worked with could be installed at any position of the tail shaft. So just slide it off, be ready to catch any fluid that leaks out, replace the seal and slip the shaft back in. Good luck.

I think you mean the yokes and not the u-joints being welded. And yes the slip yoke at the trans can go in any way unless it is keyed as mentioned above. It is best to reassemble at the pinion the way it came apart. So mark'm and put'm back the way the came out.