4X4 help. Front end not locking in.

I have a 2001 Tacoma. 4x4 5 speed. Manual transfer case. I’m having a problem getting my front end to lock in. When I’m sitting still and put the truck into 4lo it shows on the dash that it’s locked in. The transfer case does its job and gears the truck down and spins the front drive shaft. But the front end isn’t locking in. I’ve takin the actuator out and tested it and it moves freely. Hopefully someone has the answer thank you.

 

You have automatic locking hubs I assume? Sounds like they are just not working. How did you test the actuator? Also - what do you mean truck gears down when you put it in 4wD? Are you talking about 4 low because it doesn't gear down when you put it in 4H.

 

This diagnostic page should help
https://www.tacomaworld.com/threads/transfer-case-transfer-cases-in-first-and-2nd-gen-trucks.345652/

When you select 4x4 , do you get 12 volts to the plug on the front actuator ? Check it with a test light
If you are getting voltage to the actuator , what condition is the shift fork in ? Did you manually try to shift the fork to the 4x4 position ?

 

I tested the actuator by taking it out and while it was still plugged in had someone shift it into 4wd and the fork slides back and forth.

 

The most common problem with auto hubs are a lack of maintenance . Take them apart , clean them up checking for wear . Give them a light coat of lithium grease and put them back in

 

I have the Add (automatic differential disconnect) so I my main problem would be with the front differential correct? If the when I put the transfer case into 4wd and the front drive shaft spins and the actuator fork moves everything up to that point is working like it should right?

 

No I don’t hear anything.

 

The shift fork has a sleeve that it slides into place, did you check that that sleeve moves freely by hand. You can Engage 4wd by hand if you move that sleeve.

 

I am having problems with my actuator. I checked the voltage and I have zero on the two pins that power the motor. I know the ADD itself is fine because a 9 volt battery will slide the fork. I however have no voltage coming through those two important pins. Do you have any suggestions? I feel like the only thing to do is follow the line back until I find the break.

I only wonder if the transfer case differential may be acting up and then cutting all voltage to the front ADD? Is that possible? however, the other circuits on the ADD hold at about 13v.

 

Follow the wires back to the switch on the transfer case .
When you select 4x4 , the switch on the transfer case supplies the voltage to engage the front Add .
Sometimes the switch gets mechanically stuck in the 2 wheel drive position or like mentioned , the wiring can have a break in the line .
Pull the transfer case switch out and make sure it isnt seized up .
Check for voltage at the switch on the transfer case