Toro Titan won't move need help

I just purchased a used toro Titan with a 60 inch deck . The guy I bought it from tried to change the drive fluids managed to drain them and install new filters in it along with oil but said he couldn't open the vent plugs on the drives. He tried to get it moving but said he couldn't figure it out and just bought a new machine. I bought it anyways thinking it would be a quick fix(I was wrong). I managed to open the vent plugs and had fluid coming out wheels started to turn after I followed the instructions in the manual but when I gave it throttle the wheels stopped turning. I managed to get one side working(left side) but when I give it gas it stops again. but the other side I'm getting nothing. I'm looking for any info or ideas as for what to try next. Could he have burnt out the drives and if so where do I find replacements? Paid next to nothing for the machine so I think it's worth fixing