What's wrong with my car?

My car took and smelled a little smoky underneath it for a couple days but for some reason I was being retarted and ignored it. I drive a white isuzu trooper made in 2000. Ad tonight I was driving back and it sounded like it was skipping out between it's shift between 2nd and 3rd gear I think and it sounds bad. When I got out i looked under the car and it was smoking and it looked like it was coming out of the exhaust towards the motor... It seems like it would have to be a transmission problem though. Thanks for all the help everyone!