[gpetilli]

What are you using to drive the motor? We have had half an H-Bridge on the speed controller fail which then can drive only one direction. Does it drive the opposite direction if you swap the motor leads to the speed controller? Does it work connected directly to the battery?

Also, if you are using Jaguar, it has two limit switch inputs that can keep it from running in one direction - although that should not make noise. Check the limit switch jumpers anyway.

Does the speed controller LED color change to indicate you are commanding both directions? Red, yellow green?