aeveringham

Hey guys. I'm hoping somebody on here has some experience troubleshooting problems with the ADD system!

I have a 1991 pickup, 3vz-e engine. Manual transmission. live hubs. I bought the truck last summer stupidly assuming that the 4wd worked. The seller said that it had just been serviced! I guess they failed to mention that the problem wasn't fixed. Anyways, winter just rolled around and I discovered that when shifting to 4h, my 4wd indicator light flashes, and then stays off. When steering in 4H I don't notice any tension on the wheel. Of course 4L feels different because of the gearing. Recently I've been reading around online and trying to learn as much as I can about the ADD system.

Here are the links I've found most helpful...
http://www.off-road.com/trucks-4x4/tech/the-automatic-disconnecting-differential-system-19259.html
http://www.gvrdeu.org/Toyota%20Manua...26addcontr.pdf
http://www.4x4wire.com/toyota/tech/add/

From other forums it sounded to me like it was most likely a corroded vacuum hose or electrical problem. I haven't done any electrical testing yet, but I've inspected the vacuum hoses going from the actuator to the solenoids and everything is intact.

*** Today I was driving home from work and randomly decided to shift into 4H while in gear and moving. Cant believe i hadn't thought to try it before. My 4WD indicator light stayed on! And I noticed that there was tension in my steering while making sharper turns. 4WD was on. I played with it in a parking lot for a while and found that:
1.) 4WD only engaged when I shifted into 4H while moving. Both in gear and in neutral. (didn't want to try 4L while moving.)
2.) 4WD didn't always engage while moving. But most of the time it did. Sometimes the 4WD light would flash as it does while truck isn't moving.
3.) 4WD SOMETIMES would automatically disengage when the truck stopped moving. It was kinda hit and miss.
4.) ONLY while moving, when i would shift back to 2H from 4H, a loud clunking noise coming from my transfer case would happen. Not sure if thats a normal occurrence or not.

So, I'm a little baffled by this problem. Why would my 4WD only sometimes work while moving? Don't get it. I'm about to go check some of the electrical connections in my ADD system, but who knows where the problem actually lies. Any ideas? I'd greatly appreciate any help I can get! Thanks for reading...

Smaay

still sounds like you might have a vacuum leak. i ended up deleting the ADD and bought a set of used ASIAN locking hubs. I prefer getting out and locking them just knowing they are engaged