The Tailshaft Seal... Again

[Krank88]

I have owned my 88 Astro Van for 7yrs. It has had the tailshaft seal replaced 3 times as a result of leakage(the last time about 1 1/2 yrs ago). I asked my mechanic to change the front u-joint in case it was causing a wobble. Did not replace the back because he said it was ok. They changed the seal, a"joint" inside the housing and an o-ring. Now it is leaking again. Could the back u-joint(which has no symptoms of failure) be causing a wobble? Could a new tailshaft housing be the solution? Would I have symptoms(vibration) if the driveshaft was out of balance?
Unfortunately, I am unable to fix it myself, other wise I would keep putting in a new seal. The car is driven mostly locally and seldom on the highway. I have driven it 20,000 miles in the last 7yrs. Any Ideas would be appreciated. Thanks in advance.

[Smiliesafari]

If you replace the extension housing bushing, seal, and driveshaft yoke your problem will be fixed.

[Krank88]

If you replace the extension housing bushing, seal, and driveshaft yoke your problem will be fixed.

Thanks for the reply. Yes, the bushing(which I erroneously called a joint) and the seal were replaced on several occasions. The yoke was the only thing that was not replaced in the previous repairs. The seal and bushing repair held for usually a year or two, then the same old leak reappeared. It is probably the original yoke with the van. Thanks again, Smiliesafari.

[LiftedAWDAstro]

Make sure there isn't fluid coming out the tiny hole in the end of the yoke itself. I remember Lockdoc (I think) had a small leak and found the yoke had a tiny hole. RTV'd it and no more issues.