When my t100 gets warm it won't go into 4wd. I believe it may be the A.D.D. Solenoids(vacuum switches vsv2 and vsv4). I have verified that they have the corrrect resistance and flow, but the local toyta repair shop said they could still be malfuntioning, cause I can get it to lock in when I remove one of the hoses on the diff. Can anyone help me find these vsv valves, I really don't want to switch over to manual lockin hubs?