Hello,
I am having problems with the ADD system lately. My 4runner has manual hubs but I have not disabled ADD completely yet. When I put the shifter (automatic trans) in H4 or L4 the t-case always engages but the front axle (pass side) does not. If I try it a few times sometimes it works eventually, sometimes not at all. I have noticed if I can coast down a hill in 1st gear and then shift into 4WD it will engage sometimes. I think it is a vacuum problem but I am not sure what to look for. I've taken the vacuum lines off and there does appear to be vacuum coming from the engine (where it goes into the check valve). Any help is appreciated so I can still use my 4WD before I tear all the ADD stuff out.
Thanks,
Bryan

 

Do you hav a manual for your rig? I would look at the vacuum check valves. Seems not enough vacuum is being produced to make the change. Or the fork is getting stuck, and it not being allowed to smoothly slide.....

 

I've checked the vacuum check valve against the passenger side fender. Actually I replaced it and it didn't help.

If I pull the hose off the vac side of the valve and suck on it, the shift fork seems to have no problem moving the sleeve, and the front locks up fine.

Maybe my engine is not producing enough vacuum for some reason? What about that multiport valve that the vac line plugs into?

 

Hmmm, if you can manually move the shift fork via the vacuum line and lung power, seems it may be an electrical issue. When you shift into 4wd, you should get an electrical singal to the vacuum solonoids to allow the sucking to begin. However, if the solonoids are not getting the signal, then no vacuum would be applied to the shift fork. How about putting a inline with the vacuum solonoid to see if they are getting a signal when you shift into 4wd. If they are, I would look at the vacuum, seems you may not be getting enough vacuum to move the shift fork. Could be you have the vacuum lines plugged up somewhere upstream of the solonoid.........

 

I am thinking as soon as it's not 12 degrees outside and I have some spare time I am just going to tear out all the ADD stuff. The vac lines don't seem to be plugged with anything.

I'll check out the possibility of an electrical problem later on today, if I don't find anything I guess I'll continue to suck it into 4WD until I can remove all the ADD vac/electronics, I have to get out to lock the hubs anyway...

Thank you for all your input SteveO.

 

Is it really that cold over there? Have you heard of the ACW there in Prescott?

 

Well it's 18F now, 13 with the windchill. This winter has been very mellow for central/northern AZ. We got our first snow a few days ago and a little again yesterday which didn't add up to anything. I went to Jerome on Wednesday and Mingus Mtn. had less snow/ice than downtown Prescott.

Hmm, I don't think I've heard of the ACW, or I just can't figure out what it stands for. What is it?

 

ACW = Arizona Christian Wheelers

they have a forum as well.

 

Ah ok. I hadn't heard of them. I recognize that SAS Tacoma in some of the pics, seen it around town. I only viewed the pics from Alto OHV, having dialup is a drag.

Kind of makes me want to go up there again, it's only about 10-15 mins from my house.

I am surprized they don't have any runs on the local FS roads listed. There are some good trails around here, from easy 2WD to lift and lockers.