4WD HI not working

[regulator213]

Ok, So... I have been trying to pinpoint the issue with my 4wd HI on my 1999 SR5 and wanted to share this short story about the dealership.

4WD Lo works, the light comes on and everything.

I tested the voltage at the VSV's and noticed that the engage VSV does not get power when shifting into 4HI but it does in 4LO. If I switch the vacuum lines around 4WD HI works fine and the ADD actuator works but I don't get the light. Also, when the light comes on in 4LO, the front drive shaft locks up but does not in 4HI.

This makes me think the 4WD Hi position switch on the transfer case isn't working anymore. Which is why the VSV solenoid isn't getting voltage when shifting into 4HI.

I dropped my truck off at the dealership for some other stuff and asked them to look at it while it was in there and they swear up and down the ADD actuator is bad. They said that the two vacuum lines going to the actuator has nothing to do with it engaging those are just breather tubes. They also said that power at the VSV solenoid is not what engages the ADD actuator but actually the ADD actuator is what sends power to the solenoids. This goes against EVERYTHING that i've read about the ADD system so far. Am I really that far off or are they?

I told them everything I had found thus far and they pretty much told me the guy working on it has been a master tech for 13 years and he knows what he's talking about and he's POSITIVE the ADD actuator will fix it.

What do you guys think about all of this?

 

[pluton]

Unfortunately, once they start in with the jibberish tech talk, you can no longer trust anything they tell you. It's made worse by the dealer system of having to deal with the service advisors instead of the actual guys who do the work.
This sounds like my last dealings with my local dealership service department: On the 5th redo of the rear axle seal job, they told me that my axle breather( which I had checked just before bringing the car to them) was clogged. Wrong is right, up is down, Alice In Wonderland. They're pretty much useless to me now.

 

[regulator213]

Thats pretty much what I had understood of dealerships in the past. Thats too bad that this is actually the case. Its so hard to find a solid auto mechanic anymore. I'm glad that I knew the system better than to just say "OK, if you say it'll fix it"

They Also told me that the front driveshaft locking up has nothing to do with the ADD system engaging but actually the transfer case switching into 4WD. I know this is also crap because if you actuate the ADD system manually and leave the transfer case lever in 2WD the front driveshaft will lock up and vise versa when you manually unlock the ADD system.