Hello, my truck was kinda vibrating, almost like it was on a rumble strip between 40 and 60, for a couple days. This problem didn’t happen while in 4wd. Today it suddenly stopped vibrating but now 4wd dosn’t work, any thoughts? I figured vacuum lines however that wouldn’t explain the vibrating. It’s really cold here in AK so trying to not do to much diag outside if possible

 

Does your truck have manual hub dials for locking front hubs? I didn't think that 1986 had the vac operated differential disconnect. The vibration could be u joints, cv axles, or maybe even wheel bearings. What makes you say 4wd doesn't work? Can you tell the front tires are not pulling?

 

tried to get up my driveway but it was just spinning back tires, found out my suspension was kinda f’ed (see pic). Auto locking hubs, transfer case is engaging just fine (front driveshaft spinning while in 4wd) but no power to front tires. Currently chasing solenoids and vacuum lines to front diff actuators but it seems endless. We are unsure what the electrical system actually does for 4wd so answers on that would be great

 

I have a 2nd gen 95. I did an engine and trans swap. My 4wd was not working (the light on dash anyway). The xfer stick would engage - I could see the shaft turning peering thru the floor tunnel.
Finally realized I had swapped to connectors (don't recall names off top of my head). One 'registers' its in 4wd by closing switch on right/drinkers side of transfer case. The other, on the left/driver side detects 4Lo/Hi. Closed is 4lo. The 2/4 switch on right side closes when lever (manual trans, sorry. Not sure about autos). When diagnosing I realized that closing that switch by hand (engine etc off, no noise) I could hear a relay up under the radio stack somewhere actuate. That relay (maybe indirectly, no sure) activates the vacuum solenoid switches on on right fender well, causing vacuum to pull the ADD sucker diaphragm one way, and I think, release causes the vacuum actuator on the OTHER solenoid to pull the ADD sucker off (off front diff connect). There is an ADD detect switch (lookes just like the 4w and 4LO detectors) on the front of the front diff, that closes when the ADD actuator has sucked it to "engaged". THAT switch lights the 4WD light on your dash. All assuming you have a 94 or 95. but likely any 2nd gen 4runner.

My fix was easy, I had just enough extra length in my harness to swap them. They are identical connectors on the xfer case.

 

so we might have fixed it, light dosn’t work but I’m going to chalk that up to the wires being frayed on the front of the diff. Havnt tested it yet but can hear actuator…. Actuating. There was no vacuum going into solenoids but there was coming out of blue canister (see pics.) so we teed off that and just blocked off the original line that didn’t have vacuum to keep the system pressurized in case something changes. We have no idea what is past this system but engine runs fine so….

Diagram of what we did

Vacuum lines above the solenoids (passenger side)

 

How is everything now?

 

4wd engages fine, light comes in and everything. Still not sure what went wrong to cut off vacuum to the solenoids but the bypass is working fine and everything seems to be working as it did before. Will let y’all know if something goes wrong with our diy fix