IFS 4WD not engaging (ADD)

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DanS HJ-45

DanS HJ-45

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OK, got a limited amount of time to get this fixed. My 4WD isn't engaging, and it has to do with the ADD on the front "axle." I have good vacuum to the solenoids, and some vacuum coming out of the front (2WD) solenoid, but nothing detectable from the rear (4WD) solenoid valve. It seems like either the vacuum line has a plug in it prior to the ADD solenoid valves, or the ADD actuator has gone bad.

I'm going to take the multimeter to it tomorrow to make sure the 4WD ECU is commanding the solenoid valves to move, but they "seem" like they are.

But I've got to get this fixed FAST, because I head off to work on Monday and have essentially spoken for all of my free time before I leave for the 45 run, and I understand I'll need 4WD to make it to the site.

Could I go the junkyard and snag some parts from non-ADD trucks to simply bypass the ADD actuator? I've got Aisin hubs, so I don't exactly need or want the ADD system at all.

This is all just temporary anyway. I recently "acquired" an '85 axle housing.... ;)

Dan
 
If you have the time, I think you can just bypass all the solenoid stuff and send manifold vac to the actuator on the axle since you have locking hubs (it'll be locked all the time). And if worse comes to worse, you can probably make camp without 4wd, the first section of trail isn't that bad. Then we can figure it out while I poke around your truck, which I'll be doing anyway! :cheers:
 
I may fiddle with that tomorrow to see what's up. Of course there'll be fiddling. It's the best! I know that it is possible to manually engage it and then use a hose clamp to tie it in that position, so I may have to try that.

If I called in sick for one of the trips I bet I could get the SAS done before then maybe.... :) But that's risky, since I am hoping to buy one discounted without springs so I can get some custom made ones to minimize the amount of lift.

Hooray for tinkering with it tomorrow!!!

Dan
 
I don't know the reliance here but I'll say it and maybe if it won't help you, it might somebody else.


I don't remember what made me do it but I did hot wire the diff in my T100 once. All I did was take a vac puller (the gun type thing) and place a vac on what I think is the right side(there are two and I presume it wouldn't work if done on the wrong side). I then kinked the short piece hose in my fingers, then placed something to block the line then let go. I already had manual locks on it at the time and to my astonishment it worked fine.

The diff was locked at all times but the hubs just made it like a normal non-ADD diff.
 
Ya, just take a Miti-Vac and pull a vacuum on the dashpot to manually engage the diff, then leave it that way, use your hubs to engage the CVs.
 
Hilux said:
I don't know the reliance here but I'll say it and maybe if it won't help you, it might somebody else.


I don't remember what made me do it but I did hot wire the diff in my T100 once. All I did was take a vac puller (the gun type thing) and place a vac on what I think is the right side(there are two and I presume it wouldn't work if done on the wrong side). I then kinked the short piece hose in my fingers, then placed something to block the line then let go. I already had manual locks on it at the time and to my astonishment it worked fine.

The diff was locked at all times but the hubs just made it like a normal non-ADD diff.
Click to expand...

That's fine, but when you loose the vac in that little line, the odds aren't good that you'll have the stuff to fix it.... and you may be needing it at that point.

That's why I like the manifold vac better for this mod.
 
I like the MityVAC method idea. I'll probably carry the VAC with me "just in case" even if I also go with the manifold method.

Knixen: I am sure that the 4WD isn't working. I actually figured that the indicator had died, so I kept driving. When I couldn't cross an obstacle that is normally no problem is when I realized that the 4WD was actually not working. It also doesn't bind at all on concrete roads, so I'm sure it's not engaging. I can get the transfer case to engage (it's an electric 4WD selector on the T-case), as with the 4WD "engaged" but the hubs out the driveshaft still turns.

Dan
 
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