What You Think?

Just got the car drove grate then it rained the other day and when I went into third it seem like it was no longer pulling?it wAs still moveing but it seem like the cluch was slipping or some thing it's never done that befor ? Any ideas and is the cluch out ? And why dose it seem to run hot? It not leaking any coolant i can see but think some one put cooper seal in the radiator befor I got it? It's 94 gt manual