front seal almost definitely. R and R of a tranny is expensive for a $3.00 seal. I would try a pint of stopleak and fingers crossed. It should delay the R and R for a while at least until the rebuild.
2005 320 CDI
2006.5 VW Jetta TDI
1991 560SEL (179000 Sold)
1972 280SEL 4.5 ('The Lead Sled' 320000 miles when sold.)
1972 220D (225000 when sold)