My daughters 2003 Chevy Tracker made a horrible grinding, clunking type of noise yesterday and it would hardly go forward. She got it home somehow, God's help. This morning I started it up, ok, put it in gear ok stepped on the gas and horrible noise and did not want to move. Put it in reverse and no problems at all. Is this a transmission issue, low fluid or?

This sounds more like a brake problem to me I mean if the transmission is not makeing noise when the engine is running in park or reverse put it in drive with the applyed and if you don't hear the noise and then you hear the noise when the vehicle is moveing . It is most likely something wrong with the rear brakes . One of the shoes a hold down spring has broken or a bearing issue parking brake issue . Check the transmission fuild it should be red and not have a burnt smell to it or small peices of metal on the dip stick to be sure But this sounds like rear brakes good luck

Check the fluid to see if it is brownish vs reddish. If brownish, the transmission is overheating and mostlikely needs to be rebuilt. Good luck