Chevrolet Repair: transmission/transfer case question, diesel 4x4, case question

Question
Hi there,
I have a 6.2 liter chevy scottsdale diesel 4x4 pickup, 1983.  About a month
ago it sprung a transmission fluid leak from the seal where the drive train
goes into the transfer case, but i kept having to add fluid to the
transmission....  I finally replaced that seal, and now 400 miles later it is
leaking again, and I find out there is a seal between the transfer case and the
transmission that keeps those fluids separate.  Maybe this seal is bad, and
the tranny fluid is leaking into the transfer case?  
how much damage could i have done by driving those 400 miles with the
fluid draining into the transfer case like that?  Also,  there is no mention of
this other seal in the chilton manual, so I am wondering what information you
can tell me about changing this seal.. I assume I will have to drop the transfer
case?  
Thanks alot,
amanda

Answer
A leak between the transmission and transfer case wouldn't cause the tailshaft seal to go out. I would replace that seal again, and replace the bushing there as well. It is probably allowing the driveshaft to have too much lateral play, and damaging the seal.

There should also be a vent on top of the transfer case. Make sure it isn't plugged.

Van