[pandrade]

ohh its the ol slushbox.has the previouse owner said anything on how often he performed a tranny flush and changed the filter packs?(if this tranny has a filter)on my auto's i do it every 50k miles to enshure good performance and econ.if its never been changed i would leave the old fluid alone once that stuff gets old and glazed on the parts flushing the old fluid and adding new fluid which contains new detergents might result in more damage( i would still top it off whith fluid if low).

im not an expert tech but just a thought here is that maby the passages in the tranny are all clogged up and once the fluid gets hot it becomes viscouse enough to pass by the passages(as well as the metal could expand and let old fluid and debres pass)