Hi, i have a 2007 gmc canyon with a 3.7?

hi, i have a 2007 gmc canyon with a 3.7 and my transmission just started screwing up, my drive and 3rd gear wont work and when i put it into them it makes a grinding noise but when i go into 2nd or 1st it goes and when i reach about 40km i can switch it into drive and it would work, but as soon as i stop it wont work.