'96 Tacoma 4X4 Auto - Sticking Actuator

[kennyyoung]

Ok I got a theory. I'm thinking that if the position sensor switch is sticking (the ball bearing is not freely pushing up and down). When the shaft going into the transfer case is in 2wd, the the ballbearing should be down (fully extended and in a notch on the shaft). When you engage the shaft into the transfer case, the ballbearing should come out of the notch, slide along the top of the shaft, pushing it up into the position sensor switch to illuminate the dash light. If this is the case, when we are in 2wd the ballbearing is down into the notch ... if the ballbearing is sticking, it wont let the shaft push out because its down in the notch and doesnt have enough power to push the ballbearing back up into the position sensor switch, therefore not allowing us to engage 4wd or illuminate the dash light. What do you think? Basically, the position sensor switch is holding the shaft from moving!!!

[kennyyoung]

Just a picture I have drawn up..... seems logical!!!

[taroy1]

Could be. Seems that the switch is normally open in 2WD mode and closed for 4WD. So, if I just unplug the connector from the switch and jumper the leads in the connector, it will simulate the closed switch and hopefully turn on the dash light.

[kennyyoung]

When you say jumper the leads, you mean basically join the two with a short piece of wire to create the circuit? Is that right?

[taroy1]

That's it!

[taroy1]

I thought I'd try some easy stuff tonight and managed to make some progress. Here's what I did.

1. chock the front wheels
2. put her in neutral
3. release the parking brake
4. jack up the left rear corner until the tire is off the ground
5. put in the key and turn it on for power (do not start the engine)
6. make sure the 4WD button is not pushed in
7. while looking underneath, rotate the rear tire and observe that the front drive shaft does not turn
8. push in the 4WD button
9. rotate the rear tire and observe that the front drive shaft does turn

Great! For me, that confirmed that the transfer case was working fine. Mechanically, at least. I then wanted to

rule out a bad 4WD switch on the transfer case.

10. put the truck back on the ground
11. unplugged the electrical connector from the 4WD switch on top of the transfer case
12. form a small paper clip into a U shape
13. insert the ends of the paper clip into the 4WD switch connector to jumper the two wires
14. drive the truck around the block and cycle the 4WD button to see if it will engage

That produced no change for me. No 4WD light on the dash and no clunk from the front differential. I decided to move forward through the system.

15. Have someone cycle the 4WD button on and off with the key turned on (do not start the engine)
16. Using a mechanic's stethoscope or a long screwdriver with your ear on the end of the handle, touch and listen to each solenoid under the hood by the driver's side firewall.
17. You should hear a distinct click when the button is pressed in and out.

That all checked out on my truck. I can now assume that the wiring, the ECU, and the solenoids are at least working electrically. Now I don't know if I might have a leaky soleniod, a general vacuum leak, or maybe a bad 4WD actuator on the front differential. I wanted to see if maybe the system only had a problem going into 4WD but would be able to go back to 2WD. To get a better idea of the health of the vacuum lines and the diaphram in the front actuator, I thought I would try something mentioned in another thread I read somewhere.

18. Remove the two vacuum lines from the solenoids that lead down to the front actuator
19. Reverse their position and reattach them to the opposite solenoid
20. Crank up the truck to generate some vacuum preasure and give it a test drive to test out the 4WD system

Surprisingly, but puzzling, when I pushed in the 4WD button, it engaged properly with the typical clunk from the front end and the dash light came on! Releasing the button dropped it back out to 2WD. All is well! But why? One would think that the opposite would occur that pushing the button would result in 2WD while releasing the button would engage 4WD.

I need to go back and try to find that thread that I was reading. I remember that the guy said he tried the same thing successfully by swapping vacuum lines but also had no explanation. He also questioned that his lines may have inadvertantly gotten reversed by another technician while doing some other service. But in my case, I know for sure that the lines remained in the same configuration since my 4WD system used to work. In fact, it is a bit of a stretch to put the rear vacuum line onto the front solenoid which supports that fact.

I thought that this swap may have just dislodged a sticky front actuator. So, I put the vacuum lines back to their original configuration and the system would not engage 4WD again.

So, I'm puzzled but happy to at least know that both actuators (the expensive bits) seem to be functional. I'm going to drive it with the lines reversed for a while and see what happens. I'm also going to research some more to see if I can figure why this works.

I'd be very curious if you see the same result by swapping yours. Care to give it a try? Takes 5 minutes including the test drive.

[kennyyoung]

I have been under my truck this morning and here is what I found. I removed the Position Sensor Switch to see if the ballbearing was sticking.... it was perfectly fine...with it still out, I plugged it back in and pushed up on the ballbearing....presto, the dash light came on, the front actuator engaged and locked the front stubby drive shaft.... release the ballbearing, the dash light goes out, the front actuator disengages and the stubby shaft unlocks. If the stubby shaft is locking, doesnt that mean the truck is in 4x4? If that the case, what the heck is the point of the transfer case actuator anyway? I could just bypass the position sensor switch with a toggle switch and with the push of a button, the dash light would come on, the front actuator would engage and the stubby shaft would lock putting it in 4x4. Am I right or am I missing something here? Oh yeah, your question......yeah I would be willing to try swapping my vacuum lines but you will have to explain exactly where they are!!!! Whats your take on my findings?

[kennyyoung]

If you took the electrical connector off the 4wd switch and joined them with a paper clip, the dash light should have come on, the front actuator should have engaged and the front stubby should have locked. That was the same thing I did by pushing up on the ballbearing......it created a circuit and thats what happened. You have an electrical break in the line from that connector.....thats my guess!!! But in the mean time I would like to swap my vacuum lines....could you explain where they are?

[taroy1]

I won't be home until after dark. I'll take some pictures in the daylight tomorrow of the solenoid assembly and where the vacuum lines connect.

My understanding is that the dash light will not come on until everthing is engaged (both the transfer case and the front diff) and you are mechanically in 4WD. The electrically powered transfer case actuator engages the front drive shaft with the transmission while the vacuum powered front actuator engages the front differential with the front drive shaft. So, you can have either half of the system engaged without the other and the light would not come on. The position sensor switch on the transfer case senses when the front drive shaft is engaged which signals the solenoids to engage the front differential. I have proven that the transfer case has engaged because the front drive shaft turns. But my front differential will not engage unless I swap the vacuum lines. Go figure. You might have a different problem than me because, yes, I did do the paper clip trick and that did not engage the front actuator or bring on the dash light.

[kennyyoung]

That drawing that I did in post #32 is basically how the Position Sensor works.... by me taking out the sensor and pushing up on the ballbearing, the truck thought the transfer case actuator was engaged, therefore engaging the front actuator and dash light. The problem I am having is that the transfer case actuator isnt engaging, pushing out the shaft into the transfer case...... if it did, everything would be fine on my truck. My actuator needs to come apart and I really dont want to do that!!! I will wait for your pictures and try the vacuum lines first.....anything is worth a shot!!!

[taroy1]

Also try steps 1-9 in post #36 to confirm that your transfer case is not engaging.

[kennyyoung]

Will do, first thing in the morning ..... that is if the snow lets up.....15cm so far today!!!lol

[taroy1]

Here are a couple of photos of my 4WD vacuum solenoid assembly which is mounted to the sidewall on the driver's side right behind the battery. You can see a vacuum line coming out of the top of each valve and going down to the left. I simply twisted and pulled on each line to remove it and then swapped them.

[kennyyoung]

I never had a chance to try the vacuum hose swap today.... hopefully tomorrow!!!

[kennyyoung]

Ok, I came across another problem before I swapped those vacuum hoses..... the magnets in the actuator motor came loose in the motor cap. I had to epoxy them back onto the cap and put everything back together. If your gonna pull the cap off and check yours, becareful that the stator dont come out with the cap.... if it do, you will have two brushes to get back into place and it aint fun!!! Just got it finished, now I got to wait for the epoxy to dry for 4 hours before I can crank her up and try the 4x4!!! Fingers crossed!!!

[dirtrider612]

i had the same problem with my 99 tacoma. i guess the guy before me never really used the 4x4 so i took it to big o to check it out cause i knew nothing about the ADD system. the guy knew nothing about it as well so just tried a bunch of things. the way he fixed it was pushing air through the system with an air pump. i believe he said it took about 15 pounds of air pressure.
just make sure once you get it working you use it atleast once a month just to keep the actuator moving.
hope this helps out.

[kennyyoung]

Ok tried the truck this morning, pushed the 4WD button and perfect, the truck engaged into 4WD..... only problem is, now it wont disengage!!!! Maybe the epoxy wasnt strong enough to hold the magnets on!!! So, I crawled under the truck and unplugged the position sensor switch.... it disengaged the front actuator and took it out of 4x4.... the rear actuator is still engaged into the transfer case therefore the front stubby will continue to spin, but at least its out of 4WD. I think im going to bypass the position sensor switch and put a toggle switch in the cab to control the front actuator giving me 4wd on demand!!! After I install the toggle switch, would it be OK for me to unplug the t-case actuator to make sure it doesnt try to disengage anymore... it would be permanently engaged????

[taroy1]

I would be concerned that having the transfer case always engaged and the front driveshaft always spinning might add wear to the system. It would also likely affect your gas mileage.

After playing with mine for a little while longer, I have determined that swapping the vacuum lines is not a viable solution. It does in fact reverse the effect on the front differential because after making the swap, I found that when I thought I was in 2WD that the front differential was engaged with the front driveshaft. The transfer case was not engaged so the front driveshaft was just spinning whenever the front wheels were rolling.

With what I know now, I am near certain that I have a vacuum leak or bad solenoid up front. The side that is bad is the one that engages 4WD. I will confirm this after my order for a hand vacuum pump and guage is delivered.

dirtrider612 is right, once it is back in operation, use it occasionally on a loose surface or wet road to keep the lubricants moving around.

[kennyyoung]

Yes, I figured that having the transfer case always engaged and front driveshaft always spinning will add wear to the system, but I am getting rid of the truck in May or June of next year.... I only need about 6 months out or the 4wd system so I am hoping it will last that long!!! Winters around here, I am in 4wd most of the time anyway!!

So, you are sure that your t-case actuator is working? If you can get your front actuator to engage, all that is left is for the t-case actuator (and thats an electrical actuator) to engage to be in 4wd and the dash light to come on!!!

[kennyyoung]

Taroy1, have you solved your problem yet... I finally got mine fixed (to a certain extent), with the help of a toggle switch. Once I got the t-case actuator engaged, I unplugged it and ran a toggle switch from the cab to the position sensor switch..... basically bypassing the t-case actuator!!!! So, all I got to do now is flick the toggle switch and the front actuator engages and gives me 4x4..... flick it again and it disengages. The t-case actuator will remain engaged 24/7 and so will the front stubby shaft, but at least I can toggle between 2wd and 4wd.... better than nothing!!!!

[taroy1]

Good creative solution. Glad it worked for you. While I waiting for the hand vacuum pump that I ordered to arrive, my time has been diverted to painting our dining room. 'Tis not nearly as fun as tinkering in the garage.

[kennyyoung]

Tough break.....that vacuum pump better get there soon to get you out of the dining room and back into the garage...lol!!! I have a much better understanding of that t-case actuator now and how it works....if you have any questions.... you know where to ask!!! Good luck!!!

[4x4CPOSEADOG]

Originally Posted by kennyyoung

Tough break.....that vacuum pump better get there soon to get you out of the dining room and back into the garage...lol!!! I have a much better understanding of that t-case actuator now and how it works....if you have any questions.... you know where to ask!!! Good luck!!!

So you finally solved your problem? Congrats then

[kennyyoung]

Thanks 4X4CPOSEADOG, it was a long haul and alot of digging for information, but with a lot of online help, I finally found a way to get around my problem!!!! Thanks to all who offered input..... it was greatly appreciated!!!