I have a John Deere LT 190 riding mower I change the belt and pulley on it Now it won't engage correctly the tires will engage but only when lifted off the ground But you can stop them with your hands I check to be sure the key was in properly and it is Does anyone have any ideas what else can cause this problem ? I don't feel it is the transmission since it was working fine before I change the belt

Check your belt tension , sounds like its not tight.

Thanks so much turns out you are part right lol
First error the so called lawn mower repair person made was he didn't know there are TWO keys not one there is one in each axle... also the belt was loose turns out the tension pulley has a bracket it slides into Im so glad it wasn't the transmission as he had said Yay thanks again for all the help

:)