Hey guys. I have a 2002 sonoma 4x4 with an issue. The four wheel drive doesn't seem to in gauge properly. It all started a couple months ago. I would hear a noise while driving down by my passenger front tire while just starting out to drive I would slowdown applying the break and just before stopping something would click in and everything would be fine. The last two times were different. It started happening while i was driving not just pulling out so at that point i drove to my mechanic. He took it for a drive and when he came back he said that it seemed like it was trying to in gauge itself into four wheel drive. He said that all he did was hit the four wheel drive button and then hit the two wheel drive button and it corrected itself. I drove it for about a week and it started happening again so i took it back to him. After he worked on it he told me that the switch at the transfer case was sticking. I saw it and in deed The ball at the end of the switch was stuck. I thought problem solved. Today however while driving the same thing happened. I drive home and looked at the vacuum actuator under the battery. Here is where i'm confused. While the truck is in 2 high the plunger pushes in and when i activate 4x4 the plunger slowly comes back out. I took off the vacuum line and i had vacuum sucking in while in 2 wheel but nothing when i put it in 4wheel. My question is should i have vacuum while in 2 wheel shouldn't i only have it while in 4 wheel. I'm scratching my head with this one any help would be great. ?Thanks.