4x4 not engaging

Got a 1996 taco 2.7 manual transmission manual 4x4 shifter.

When I shift into 4x4 the light will not come on and the front wheel wont engage.

Think its something with the front diff, check the vacuum lines they seem fine.
What else can u check before i tear the actuator off the diff?

Is there a relay for the 4x4?

 

Welcome to TacomaWorld
If the air vent hose is off of the actuator moisture gets in and corrodes it.
Check the 4wd position switch and connection on top of Tcase passenger side.
There are 4wd selnoids in engine compartment that turn the vacuum on and a vacuum accumulator tank on drivers side wheel well.

 

I saw there is a hose that goes from the charcoal box down to the diff but it not connected to anything.

The front drive shaft engeages so not sure if it be the sensor on the t case.

Is there a sensor on the front diff, and if so is it the same kind?

 

No sensor on differential,
The ADD Actuator has a switch which turns the green 4x4 dash light on when it fully engages the differential.
Jshift engages the FDS
4wd position switch sends signal to relay which switches vacuum on at ADD Actuator.
UNLESS
You have free wheeling front hubs (manual locking hubs), in this case you don't have ADD front differential.
(Automatic Differential Disconnect)

 

@turtle142
Does this hose have a breather vent on top? Little metal 1way valve cap.
"I saw there is a hose that goes from the charcoal box down to the diff but it not connected to anything."

Do you know the difference between a charcoal cannister and Vacuum Accumulator tank ?

 

Hmm... I would check to see if vacuum is being applied to the ADD, VSV solenoids may not be working correctly or hoses might be disconnected or have holes. If you can't find anything wrong, I'd put the vehicle on jack stands and apply vacuum directly to the ADD actuator and see if the front wheel locks, if not it may be the actuator itself.

 

Its automatic locking hubs, not manual, ill look for a breather tube on the top.

If the 4wd position switch is bad whould that cause it from not locking ?

Also i see the charcoal box but dont know what the vacumw acxumlater tank looks like.

Where is the relay located that sends the signal to the actuator?

 

What do the 2 electric wire go to on the front diff?

 

Accumulator tank is in drivers side wheel well towards front. It's a small cylinder about the size of a long oil filter. 4wd vacuum switch for ADD is dependent on 4wd position switch, connection and wiring.
Follow the vacuum hoses to find the relay/switch and vacuum tank.

 

Transmission control module under passenger side kick panel. The wires turn the green 4wd light on via the module when vacuum has fully engaged ADD actuator and diff is locked in.

 

Vacuum ADD has 2 wires
Electric ADD has 6 pin harness plug.

 

@turtle142
"Where is the relay located that sends the signal to the actuator?"
Vacuum ADD actuator doesn't get electric signal.
It's vacuum actuated.

 

I should start by checking the switch on the transfer case and go from there?

 

Easy enough with a multimeter.
Unplug and test the switch side while Jshift in 4hi. You're looking for no continuity in 2wd,full continuity in 4wd.

To test the ADD Actuator you'll need a hand vacuum pump. That's probably the culprit if the vent hose has been off for some time.

 

Looks like there is a switch / sensor on the front diff, would it not engauge if The switch os broken?

 

You asked this in your #3 post.
I answered in my #4 post

 

The solenoid is located on the front diff correct?

 

You have Vacuum ADD Actuator.
The front differential is engaged and disengaged by Vacuum.
No Selnoid on your front differential only electrical is a switch for green 4x4 light on dash cluster.

 

Located under hood, drivers side on top of fender in the Rats nest of hose and wire.
See post #2

 

I take it this is theses are the silinoids. Is that the air vent on the corner or am I missing a hose?

Also is there a way to test these silinoids? Ants fuses for them?

Thank you, your help is much appreciated