I was rolling around under the van greasing things today and noticed a drip at the transmission output shaft. There is a crack in the seal so I know it needs to go but there seems to be some slop in the output shaft too. I can lift it up and down a bit which is how I noticed the crack in the seal. Is this movement normal? The actual operation of the transmission is excellent.
I have been living with some sort of rotating vibration for quite a while and am wondering if I found the problem. The driveshaft has relatively new u-joints but it's quite rusty. I need to check to see if it's lost its weights.
Cheers, Steve

 

just got around to crawling under my 99 3500 van Steve just out of curiosity to this thread. I also have a drip at the rubber seal on mine but doesn't leave a mark in my parking spot, no visible crack in seal. The driveshaft is pretty firm and only slight-slight movement pushing with some force up and down.
I've also been living with a vibration for quite a while at about 68- 74 mph, but thinking mine may have something more to do with rear drums as it had an issue last year with a leaking brake cylinder and axle seal that my boss showed me about and fixed. Just never had the drums turned or replaced... probably should have by now but vibration actually has smoothed out a bit and not so bad

 

Thank you for checking, mine has a few drops of oil clinging to the bottom around that spot. I have to say that at 27 years old the gaskets and seals are starting to breakdown. I need to change the oil pan gasket soon and have already replaced the valve seals and valve cover gaskets. Even the engine and transmission mounts are toast. I guess the best before date on rubber is 25 years.

The manual calls for moly disulphide grease for the slip yoke so I am going to hunt that down when I pick up the new seal. It is possible that the people who did my u-joints a couple years ago used the wrong grease on the yoke. It's also possible that the bad mounts are partly to blame, I will post an update when I figure it out. This weekend will be a wrenching marathon.

 

I had the drive shaft out yesterday and changed the transmission seal. I found that the transmission output shaft was tight within its bearings so the slop I noticed is within the splines of the shaft. I also noticed that the splines are subjected to ATF+4 so they probably don't need to be lubricated. I tossed in a bit of moly extreme grease but not much, hopefully it doesn't result in me needing to change the fluid.

Putting the new seal back in is easy if you have the correct tool...tool can be found at the local hardware store. I also put a small bead of RTV on the seal as the aluminum bore in the transmission was a bit corroded.