Leaking red fluid; dripping from the u-joint

My 89 Astro van is leaking red fluid when parked uphill (slightly) that drips from the u-joint closest to the transmission and only from the part that is in the yoke that goes into the transmission. I dropped the drive shaft thinking wrongly that there would be a bad seal where i thought the yoke went into i thought a second piece, but it is all one piece with a collar. When parked in the garage nice and level it did not seem to leak. Any insights?

“I dropped the drive shaft thinking wrongly that there would be a bad seal where i thought the yoke went into i thought a second piece, but it is all one piece with a collar.” Right…Ask the counterman for a transmission tail-shaft seal…You were looking in the right place…