4WD Help

I am having a number of issues with engaging my 4wheel drive. And before you ask yes I have researched many threads on here. I removed the front diff actuator and soldered the motor contacts as many have done and unlike others I didn't see any evidence of arcing or loose connection at all. So to the symptoms at first I could not engage 4wd on the fly at all (almost got stuck at the beach due to this) it would just flash. Then I found that if I shut the truck off and engage it with the key in the start position but not turning the engine on it would engage but then I was having issues with 4lo engaging. After I took the ADD out and reinstalled as well as this remained the same. Then as I continued to tinker with things and constantly trying to get something to work I noticed that if I selected 4wd on the fly and then selected 4lo it would cause the 4hi to lock in then I started playing with 4lo and got it to start working. It seems like no rhyme or reason as to why this is happening as it is not failing the same way every time right now. So I decide to go to the beach and test it out now that I think I got it working consistently. I get out to the beach and try to engage 4wd and nothing just a blinking light I try to turn on 4lo to make 4 hi engage and nothing then I try turning the truck off and turning on 4hi and nothing and then finally it just decided to work. Then I tried going down to 4lo and it took a couple of times to get it to engage. I have no issues disengaging either of them. I have checked the connections and cleaned contacts at both the ADD and the transfer case actuator. I hear the relays and such click in when the switch is turned for the 4wd. I am almost thinking I am dealing with a computer/control signal issue at this point as it seems to be all over the place. Any thoughts or ideas would be appreciated.

¯\_(ツ)_/¯

 

I posted this for another member with the same problem, I can't seem to find it now to see what all happened.

I'm wondering if the switch/wiring is to blame, everyone who is going after the ADD and not getting a fix I have not seen try anything else.

Take a look at #5 here: https://gofile.io/?c=D0VnTb

When I first saw this, I thought it was odd to have a 100k+ value for a test. I would have just expected an open/closed circuit test. However, 100k would be pretty much spot on for a pull down resistor to drop 1 volt. My theory is that something is not allowing the voltage to drop as much as it should, therefor the computer doesn't know exactly what it should be doing. Does make some sense to me that with the truck off, flipping the switch, then trying to start it into 4wd it might work sometimes. When the truck is off, the voltage in the system should be a little more stable than while it is running. Could be just enough to get a clean enough signal to the computer long enough to have it engage 4wd.

The big question would be, how far off of a deviation can it go before the computer fails to recognize what is happening. For the sake of argument, assume it's looking for a 1v drop. It wouldn't make sense to look specifically for 1v, there would have to be some hysteresis accounted for, so maybe anything 500mv to 1.5v is good. Or maybe it's a lot pickier than that, my guess would be on the picky side.

Anyways, that's just my thought on it. Check the switch though as described in #5, maybe it's just a failed switch. I would be curious to experiment and maybe tack on a 10k resistor to pins 5 and 2, if the computer is looking for more of a drop, that might be enough to push it over. If it's looking for less, then I don't really know. Would have to start tracing wires at that point.