Have a John Deere Turf Tractor 12 V. The left back tire will not move, like it is locked. The right one does turn.

SOURCE: John Deere Gator 4x2 - Left Wheel doesn't move when in 2nd gear

I would replace the high/low switch and the reverse switch. One time a replaced the high/low switch and the reverse switch quit on me 2 weeks later.
You can also get the Peg Perego Gator Shifter that upgrades the vehicle.
You can get the parts and repair help at this site
http://www.shopjandl.com/kids---baby-ride-on-toys-peg-perego-switches-and-shifters.html
They have helped me several times.
Hope this helps

SOURCE: Please let me know how I can change the rear tires

My Grandkids go through these wheels every few years.
They love their Gator.
You take the center black cap off and use a socket to remove the attachment on the axle.
Here is the replacement wheels
http://www.shopjandl.com/sarp8115kny.html
They can also help you with the repair, I call them all the time..very friendly people.
hope this helps

Testimonial: "Thank you so much for the info. "

SOURCE: where can i get a rubber tires for a Peg Perego

the whole tire would be difficult to replace with a rubber one, but you can put bmx tires on the plastic wheels and that will give much greater traction, but shorten the life of the gearboxes. here is a link to how to do it.

http://www.youtube.com/watch?v=AAySJVt6bys

SOURCE: where and how do I

hi, open the hood. disconnect the battery and connect the charger and leave it 8-12 hours. if you dont have a charger, ebay is the best place to pick one up cheap!
good luck!