justin_4runner

that's in the classified area.

dutchboy

Bro...I have a 90 4runner and just experienced my front axle not locking in. Relay under steering column went bad. It's the relay for the vacuum switching valves on passenger front fender. If you can not find a vacuum leak and your trouble shooting leads you to bad VSV or a bad relay...cheat the system. I just did this and it works great. My dash light for 4x4 does NOT come on,but...do you really need it when you can feel it?
Here is link to my thread on my solution.
https://www.yotatech.com/forums/f116...es-pic-227726/
Manual Lockers won't solve your issue completely. Especially if your wallet is looking for a cheap fix rather than a front end rebuild.
Hope I might have been of some help...but yeah...chase down all your vacuum lines and look for a leak before you do anything else.

run4yota

omg SOB... thanks for the tip!... i have been under my truck all day tracing out the wiring and trying to get me ADD to kick inn.. turns out that i forgot to plug in the relay under the dash when i did my auto to 5speed swap.

thanks again

Whitetacoma4x4

A cheap fix to your light not working that I used to check my transfer case switch is to connect the two wires on side of transfer case. This will light it up. To control when to light up you can put a switch(on/off) in line with two wires.

R4unnerMan

Working on a 90 4runner 3vze as well, did the auto to 5 swap about 6 months ago all was well untill this winter after it snowed little did I know that the switch on the trans case needed to be wire at the same time i wired the rev lights. problem I am having is I still have no 4wd even after wiring the TC switch, I have vacumm at the add switch when in 4wd I also have vacumm to the diaphram on the front diff. could this switch thats on the transfer case be bad? I assume the one that is refered to in this thread is the one thats on the pass side way up top on the transfer case itself close by the shift levers (the same switch that I needed to wire)??

R4unnerMan

Unplugged the white connector that goes to the front Diff and used a jumper wire, 4wd light on dash comes on and 4wd now works, dont want this to be a perm fix so mabey that switch is bad??

drum4jc2u

I see this is late in the post but I just got here . I don't have a diagram handy for the vehicle but wouldn't this be a ground switch? and if so couldn't I run a manual switch and just use it when needed?

89934runr

OLD post, but this is just an FYI for anyone trying to fix an issue like this...

ADD SYSTEM DESCRIPTION:

1. When you shift it to 4wd L/H, that closes the 4WD switch on the trans, this enables (via the ADD relay) 12V to go to actuate the BLUE VSV on your passenger firewall (the orange/red one is to pull the actuator back, making the vehicle 2wd again)
2. Blue VSV has manifold vacuum routed through the vac resevoir, then to the top fitting of the VSV (where the two hoses are together). Blue VSV activates, allowing vacuum to pass down through the rubber lines, then the hard lines to the ADD actuator, pulling the inner fork to the right (pass) side, engaging the splines. NOTE: Blue VSV is held on / Vacuum is held on the '4wd' side of the actuator until 2wd or neutral is selected on the Tcase.
3. When the fork is slid over enough for the splines to be lined up / front diff 'actuated', NOW YOUR 4WD LIGHT TURNS ON. THIS IS KEY, AS JUMPING THE FRONT 4WD ACTUATOR SWITCH DOES NOT ACTIVATE YOUR 4WD. The process has to start from the Tcase switch, NOT the 4wd indicator switch (they are all 'dumb' on/off switches).
4. When you are done with 4WD, you select 2H... now the ORANGE (RED) VSV is activated (BLUE VSV is deactivated). This now sends the vacuum down to the left / driver's side fitting of the ADD actuator, pulling the fork toward the driver's side. This 'deactivated' 4WD, and allows the front diff to spin freely (aka front driveshaft stops moving, and if it does, it wouldn't do anything). When the fork moves over enough to be disengaged, the 4WD indicator switch open, and your 4WD light goes out. It's that easy.

Key things to remember:

1. Check your vacuum lines and basic wiring connectors first. I have seen many clogged lines, clogged VSVs, and 4WD switches (on the tcase) with frayed wiring.
2. The VSVs get their power (via the ADD relay).from the Gauge fuse (90s models). ALWAYS check your wiring diagram so as not to chase your tail.
3. A quick check of the ADD relay is to turn the ignition on (2wd), engine NOT running. See if the ORANGE / RED vsv has 12v on the non- white / black wire (that's the ground BTW). Now put the truck into 4WD H or L, that 12v should go away, and the BLUE vsv should now have 12v on it's NON-white/black wire (typically lt green with a pink stripe). if you get the voltage to switch, then your ADD relay is good.