4runner 4WD Problems

[Takemetotheriver]

I have a 1997 4runner limited with automatic transmission. I have had issued with 4x4 engaging. No problems disengaging. When I hit the button, I can hear the relay, so I assume that is good. I was told to trouble shoot the issue by switching the hoses at the vsv. When I did this, the 4wd engaged immediately when I hit the button. The 4wd worked for a while and then a few weeks later, the same thing happend...hit the button, hear the relay, no light and no engaging. I popped the hood and reversed the process by re-switching the two hoses on the vsv, and the problem seemed to go away again as the 4wd worked again for a while. Over the past few weeks, the issue has been happening more, and the hose switching is working less frequently. Also, the 4wd sometime disengages(both while driving and while at rest with the truck off) randomly. The vacuum lines look good and the rear actuator in the transfer case sounds strong and good (when it engages). Looking for insight into if it may be the vsv, the front actuator on the diff, or something else. Maybe I don't understand the system fully, but I am confused as to why the hose switching solution works less now and why it now drops out of 4wd randomly. Thanks in advance for help and advice. Pictures and diagrams other than what is in the manual would be appreciated too.

 

[TheDurk]

I have a 1997 4runner limited with automatic transmission. I have had issued with 4x4 engaging. No problems disengaging. When I hit the button, I can hear the relay, so I assume that is good. I was told to trouble shoot the issue by switching the hoses at the vsv. When I did this, the 4wd engaged immediately when I hit the button. The 4wd worked for a while and then a few weeks later, the same thing happend...hit the button, hear the relay, no light and no engaging. I popped the hood and reversed the process by re-switching the two hoses on the vsv, and the problem seemed to go away again as the 4wd worked again for a while. Over the past few weeks, the issue has been happening more, and the hose switching is working less frequently. Also, the 4wd sometime disengages(both while driving and while at rest with the truck off) randomly. The vacuum lines look good and the rear actuator in the transfer case sounds strong and good (when it engages). Looking for insight into if it may be the vsv, the front actuator on the diff, or something else. Maybe I don't understand the system fully, but I am confused as to why the hose switching solution works less now and why it now drops out of 4wd randomly. Thanks in advance for help and advice. Pictures and diagrams other than what is in the manual would be appreciated too.

Jeez, you aren't supposed to LEAVE them switched. That will put your front diff engaged full-time--2WD + 4WD--if system is broken, or engage it in 2WD and disengage in 4WD if it isn't. So what probably happened is your system started working by itself, but because the hoses were switched, the ADD went into backwards mode.

You need to start over and actually troubleshoot the problem. Hose switching is NOT a fix. You just do it to analyze the problem. Here is my post on the subject, which you may or may not be working from:

VSV’s/ADD
Don't guess at it, troubleshoot! Start at the twin VSV's (Vacuum Switching Valves) on the driver fender wall. There are two long vacuum hoses that come up from the diff, one goes to each VSV. Check to see that one of the two hose nipples on the VSV’s has vacuum (engine running, 4WD NOT engaged. If no vacuum either side, check the check valve going to the intake manifold and look for loose hoses or a hole in the reservoir. If there is vacuum going to one hose, then put it in 4WD. See if the vacuum switches to the other hose. If it does, and no 4WD, problem is the diff actuator or the line to the diff. If it does not, then just switch the hoses and you should go into 4WD. This confirms diff is okay.

OK, switch them back. Then use a test light to see if electrical signal from the TC also switches sides of the VSV. If it does not, problem is the TC, the switch on the TC, or the TC actuator, or its wiring back to the button (last two for non-J shift only). If it does, but the vacuum does not, the problem is the VSV itself.

I start troubleshooting at the VSV's because you can figure out where the trouble is without having to climb under the truck.