'99 Grand Sport with 177k & original transmission. I changed the tranny fluid and filter about a month ago. There were no metal shavings nor any sludge. Since then the tranny will shift slowly into first usually when cold. I used ATF-4 and the fluid level is good. I did not completely flush the transmission. I used about 5 quarts of fluid when I changed the filter. It takes about 2-3 seconds for the tranny to engage. Once the car is moving the tranny works normally. Prior to the fluid change, the tranny was operating normally. No good deed goes unpunished.

 

I'd take it in and have the tranny flushed.