I have an 89 single cab 3vz with manual locking hubs. I am doing some electrical work and I have always been under the impression that since i have manual locking hubs that ment I did not have an automatic disconnecting differential setup. However my 89 ewd makes it look like only the 22re came without the ADD relay... Am I just not seeing it or is it possible for a 3vz(manual hubs) to come w/o an ADD set up?

 

I'm pretty sure that if you have manual locking hubs you do not have the ADD setup. They both do the same thing. You get one or the other.

 

Mine had ADD, I put locking hubs on it. Still have the ADD, its just disabled.

 

Just because your truck has manual hubs now doesn't mean that it always did, a previous owner may have added them.

Easiest thing to do is to look at the front differential behind the skid plate. The differential itself will be on the passenger side and there will be a tube going over towards the driver's side.

If your truck originally had A.D.D there will be an actuator attached to that tube with a couple of vacuum lines and an electrical connector connected to it. If that tube is "bare" your truck did not have A.D.D.

See http://home.4x4wire.com/erik/diffs/IFS_diff2.jpg


The top is a non-A.D.D diff with the bare tube, the bottom is an A.D.D tube detached from its differential.

 

Yeah mine doesn't have any of that on it. I guess I'll use the 4cyl wiring diagram for that system.
Thanks!