There are 2 seals in/on the speedo. The O ring around the outside and a small seal on the driven gear hat's inside the adapter. Change them both, the little seal inside has a metal "snap" ring over it to hold it in place. Any trans shop should be able to get you the right parts. Also look at the plastic gear- it may have a groove worn into it. If it does, you need to replace it as well. Lube everything well with vaseline.
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