Assuming your talking about a BW 71 or 72 series,yes there is a seal there and when you assemble the flange you are supposed to use gasket sealer on the splines so it doesn't leak thru them as it sounds yours is. Doesn't say that in the manual, but an oldtimer who rebuilt hundreds of them told me that tip.
I have the manual in PDF, if you want it send me an e mail to me at the address below.
jleonard@usa.norgren.com