[woodridge]

Most likely a case of "Morning sickness". This happens when trannies get old and the lip seals begin to harden inside the drums. For a short term fix add a half pint of brake fluid to the tranny. This will soften the seals and make it work for a while longer. Add too much and the seals will get too soft and blow. It usually takes a few days of running before it helps.
This is in no way an overhaul or permanent fix, just a bandaid until you do it right.

BTW, been doing tranny work for thirty years and I know the pro's and cons of this.