I think you don't have the seal in all the way. It's a PITA to get in.
I used wire pulling lubricant to get mine in and alot of profanity. A picture would help determine your problem.

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1985 300 TD 448K
1984 300 TD 278K

1983 240D euro 240k
1994 f-250 idi turbo 330K
1986 f-350 IDI
1987 F-350 IDI

1985 JD 1050 4wd
1965 IH 3660