4wd System Operation & Help Thread

No, nothing happens when the selector switch is moved from 2H-4H-4L. I have to work in couple hours. Unfortunately, having a low mileage truck in the rust belt means nothing comes apart without a fight. I really want to test it now though. My 79’ Land Cruiser is easier to take apart than this pig.

 

These readings taken with a brand new transfer case actuator?

 

No, still trying to figure out what part needs replaced.

 

What did you replace here, just the vent line itself?

 

The whole vent line from the transfer case actuator to the TC. This was before I found this thread and figured out how the system worked.

 

If I just do the paper clip test will that be the same as testing ohms on the switches?

 

I’m not sure what you are asking?

When you ohm a switch, you are looking for a change in ohms when the switch is pressed and released.

Unless you are talking about using a paper clip to jump pins and by pass the switch?

 

Apologies for the late response, I've been busy at work.
Since it seems TL1 is stuck at 0v unplug the transfer case actuator and see if it goes to 12v, if it does you likely have a problem with the contact plate in the actuator, if it doesn't then the TL1 circuit is shorted to ground somewhere.

 

Not sure why they say 10 miles, the main thing is you want to move all the actuators fairly regularly to keep things from getting stuck.

 

I tried jumping the plugs to make the lights go out. But didn’t think to try doing both at the same time.

 

I’ll try this tomorrow, thanks.

 

The 4L switch appears to be working. When I depress the ball it goes to 3.5 ohms constantly.

The TL1 is at 12v when it is supposed to be at 0v when to 4WD switch is in 2H. I pulled the plug off the transfer case actuator and TL1 still read 12v. I am going to pull the cover off to see what I find. I hope nothing breaks, the 4L switch came out too easy.

 

Well the cap is not coming off. One of the bolts is permanently mated to the sleeve in the cap. The other two came out without much trouble. It kinda feel like I should get a actuator on order. They are saying it will take a couple of weeks to get here.

 

If you have an impact screwdriver that will help.

 

I have a impact screwdriver and a 3/8” impact driver. Are they better to use on rusty bolts? I’ve been using hand tools and twisting the bolt heads off. I figured the impact would do the same thing, only faster. It’s driving me bananas on f-ing truck.

 

Sure looks like an actuator contact plate problem based on the signals you posted, it's interesting you got 0v on the 4wd switch wires in 4H and also that the ADD appears to have locked but not closed DL2.

 

If I understand the system correctly, ADD would be locked out because the TC isn’t where it is supposed be. If the switch is in 4WD, the TC should be in 4WD, only then will ADD go to 4WD. I would be surprised if the ADD is toast too. That’s kind of how this truck rolls. When it breaks, it breaks hard.

 

I'm thinking the ADD engaged because the 4wd switch closed on the transfer case indicating the transfer case is in 4wd but since the limit switches aren't where they need to be the 4wd light continues to blink.

Without having a broken one to study the best I can do is know where everything should be on a working truck.

 

I guess I can test that by seeing if the front axles will spin.

 

Well, I finally got my transfer case actuator. It went in rather easy compared to everything else I have to fix on this truck. The 4WD is still doing the same thing. But now I’m getting different readings from the ecu.


The new readings are the ones circled in black permanent marker. The ones not circled or circled in pen are the readings from before the new TC actuator was installed. I have a new ADD sitting on the bench but wanted to see if you guys had any ideas before I replace that tomorrow. I not too excited about pulling it. It sure looks like a pain in the a**. Any help would be greatly appreciated.