4x4 not engaging

This could have been so much easier if you answered questions.
I believe what you are calling Silinoids are Vacuum switching valves.
And they control vacuum to ADD Actuator on front differential.
That is NOT air vent it's missing vacuum hose. The switches can be tested with a 9 volt battery, 2 jumper wires and hand held vacuum pump with gauge. Both switches are simple open or closed but must not leak when closed. When one switch opens the other must close. By applying 9volt the switch should click and you can blow through it but you'll need the vacuum pump to test for no flow when switch is closed by applying vacuum and watching that the gauge holds vacuum.
VSV test in link below

 

Thank you so much!

Where is that missing hose suppose to go?

 

I'd have to be there because you got some seriously jacked up mess.
Someone had no clue what they were doing.

 

I was able to fit it that vacuum line went into the engine right by the intake

 

This may help

 

Good write-up for ADD Delete
http://www.4x4wire.com/toyota/tech/add/

 

Been following your post,and I'm having the very same problem your having.Did you ever get it to work.?Everything on my truck worked fine(4wheel drive) till I had a motor swap.I get the truck back,and the 4wheel drive light will flicker on dash but wont ingage the transfer case when I shift the lever to the transfer case.I traced my to a relay behind passenger side kick panel in floor.That vacuum cluster bunch of hoses on drivers side fenderwell, is confusing to me.Im getting vacuum down to the actuator on the front differential.I think my problem is those electrical valves that the vacuum hoses hook to.Im lost,help if you care to discuss your diagnosis,thanks.

 

What if you have electric add where is the relay

 

My truck is doing the same thing but I can still put it in 4L and engage the rear locker and it works properly so would that rule out the 4wd position switch where is the relay you are referring to located