1990 toyota 4runner 4wd doesn't work

[gr8fultedd]

I'm trying to ask a question for the first time and hope this gets out to someone who can assist me. My 1990 4Runner failed to engage in 4WD this past weekend in Tahoe... No light on the dash came on when I shifted into H4 from H2 at a stop (clutch engaged). I had no problems with it last year when performing the same sequence (I think?). Any advice/suggestions would be greatly appreciated!

 

[ChildrenOfBodom]

Welcome to the forum. I moved your post from Dirtco's build thread to the Classic T4R's section, where someone should be able to give you the answer you're looking for.

 

[4runnin83]

Can you feel it trying to to engage?

 

[RiFF RaFF]

Check the vacuum lines going to the transfer case. More than likely they either pulled out, or are cracked. Either way - without a good vacuum you will not engage.

(Don't ask me how I know...hint hint)

:wow2:

 

[fourwd1]

Your truck has Toyotas ADD 4WD system.
The dash light is is triggered by a switch in the actuator on the front axle that locks the axle into 4WD.
That actuator is controlled by 2 Vacuum Switching Valves (1 to lock and 1 to unlock).
As the name implies, they are controlled by vacuum (Not the t-case).
Common failure points are the VSVs themselves, the vacuum lines to them, or the wiring to them. The VSVs are mounted on the actuator which is beside the front diff, drivers side. So the first thing to do is get underneath and check them out.
For more info there are many threads on this you can find by Searching.