thm400 speedo o-ring replacement

[CreativeNotice]

So my 82 c20 thm400 had some serious leakage. I've replaced the pan gasket (and the filter for good measure) and that took care of the major leak but there's still a little bit dripping from the speedo cable. From reading about it online I'm thinking I should replace the o-ring, but are there any other parts I should go ahead and replace while I'm in there?

[Engineer]

IIRC, there is more than one o-ring on the speedo adapter. You may consider replacing the tail shaft seal while you are back there.

[CreativeNotice]

So I've pulled it apart and there's a main o-ring around the diameter of the pinion housing that slides into the tranny. Then there's a gasket on the interior where the speedo cable connects. The pinion shaft goes there there and there is a small spring surrounding the gasket which causes it to seal against the pinion shaft.

If I can find the parts, I'm going to replace the o-ring, pinion and pinion shaft gasket w/ spring.