2001 Pontiac Bonneville SSEi with 4T65E transmission slips in 1st gear when cold...why?

I'm with Stayc, sounds like a forward clutch issue.. BTW, I have that same transmission in my transport van, I change the filter/fluid every 20k, it has 209k and counting without anything more than an axle seal installed on the trans and a 4T60E (basically same trans) in my grand am with 193k on it and never been opened... maintenance, maintenance, maintenance