Shouldn't have to pull the third to do the seal - if you are careful. Especially easy if you used a solid sleeve instead of a crush sleeve when the gears were set up. Assuming there are no grooves in the yoke where the seal rides, very lightly hone the yoke on the sealing surface with emery cloth. Else, go with a new (or newish equivalent) yoke.

-Bill
'87 4Runner w/ '96 5VZ-FE, 'Red Chili II'
'97 Taco XtraCab 3RZ-FE, 'BlackBean'
TLCA # 13257, Rising Sun 4x4 Club Land Use Coordinator
"He who stops being better stops being good." -Oliver Cromwell