i got a 2010 unison mobility 500 atv 4x4 they say it has yamaha drive components. well the problem i am having is with the front diff it engages in 4wd but when you push the button to go back to 2wd it does not go but you can hear the servo/acuator working checked the relays they are good the buttons seem to work as should. i jacked up the front of atv and checked it is stuck in 4wd

 

did you try driving in reverse? Can you watch the servo and actuator to make sure its moving correctly.

 

Ya tried driving in reverse did not disengage the servo sounds like it's working correctly someone else took off the servo/ acuator before I got it and tried to fix it but they had it timed wrong but I retimed it and checked before installing it and all three moads worked properly 2wd 4wd diff lock but when I tried to go back to 2wd you could hear the servo working but it stayed in 4wd

 

take the module off and see if you can shift by hand. then you will have a better idea of where to start looking.