I was wondering if anyone could help.........I have a 93 t100 and I have a problem with it not locking in the front differential, I have vacuum down to the unit on the axle but I wanst sure where to start next..I didnt want to just start changing parts without checking in...........any ideas where to start?

 

Get a vacuum tester, and check to make sure the actuator is good. Then go backwards from there.

 

might be sensors on your transfer case. Seemed to be a common issue in a thread in the 4runner forum.