Some English Ford speedometer housing cables have plastic end fittings which attach to the transmission by a metal fork. The plastic fittings will eventually warp by heat and pressure from the attachment fork.
( Replace speedometer cable assembly if the plastic fitting is loose around the cable housing )
Warped plastic ends will cause oil leaks even silicon sealant won't solve the leaking problem.
To resolve this defect without replacing the housing. Use a 1/16" thick washer 1 3/16" x 5/8" cut off a 3/8"
section so it would slip past the housing. Apply a bit of sealant to the plastic fitting face. Place the washer