I had the same experience as David. I pulled the splined seal out and installed the driveshaft with zero issues on a TKO II. I had to remove the engine(s) in my car a few times. Because of these engine installs and removals, I would drain the
oil from the tranny. I re-installed the splined seal to keep any residual
oil from running out of the back of tranny during the engine extract/install process several times. Never had an issue with leaking seals on the back of the tranny. Just my 2 cents.
Robert