4wd System Operation & Help Thread

Let us know what you find

 

ADD came out surprisingly easy… gear oil is very clean after being replaced in 30k miles ago

Here’s what it looked like.

Should I wire it to the battery to test its functionality before taking the plastic cover off?

Side note: I bought gear oil gasket maker for putting this thing back together, it’s supposed to hold up against gear oil better but has a cure time of 24 hours…
The 90 minute red RTV silicone would probably work fine too huh

 

Interesting it appears to be in the unlocked position, does the sliding collar in the diff move freely?
You could plug it in with it out and see if the 4wd system is happy.

Most RTV is oil resistant so I don't think it would matter which you used.

 

Yes the collar moves freely.

The actuator arm is a little tight up against the housing in the unlocked position and wiggles a little bit on its axle. Maybe this is one of those could have solved it with a hammer problems…

I’ll plug the ADD back in and fire it up and see what happens…

Other side note: I have the truck switch in 4HI because that’s what it was when I turned it off accidentally. The transfer case / front driveshaft is engaged.

 

But I guess it doesn’t matter because it should reset to whatever the switch is set to when the truck starts up

 

It's possible, if there is excessive wear on the shaft where the shift fork is mounted it could cause it to bind up.

Providing the limit switches are working properly and the Transfer Case Actuator didn't stop in a position where the limit switch signals would be invalid it should be able to figure things out and shift itself to whatever mode is selected on the switch.

 

Ok started up in 4HI and the rapid blink / lock out cleared.

still blinking and the ADD actuator didn’t move after cycling to 2WD and back…

Guess I gotta take this thing apart

 

Just make sure to mark the timing of the drive gear should you need to remove it so it can be reinstalled in the correct orientation.

 

Man this thing looks brand new! Not bad for an 8 year old truck that’s seen some decent off road

Used the wrong Phillips head initially and stripped 3 of 5 bolts… so that’s at least one trip to the hardware store. Should have broken them loose with vice grips before trying the screwdriver.

I heard a twang when I pulled the housing cover off, might have been the limit switch leads or the ADD position switch, not sure.

I even bumped the motor off the battery and it runs like a champ, both directions.

Im out of light and energon for this evening. Will pick it up tomorrow.

The only thing I think I have left to do is fiddle with the actuator gears and arm and see if it’s just stuck?

 

It does have a spring in it that acts as a wait mechanism so the actuator can move to it's position and then the spring moves the fork once the splines line up on the axle, I wonder if what you heard was the spring unloading.
Can you rotate the gear that drives the fork freely and does it move the fork?

 

That’s a really good call. I’ll have to check the gear and the fork first thing, thanks!

I did notice when I was covering the differential for the night (and incoming rain potentially) that the collar in the differential only goes to about halfway towards the driver’s side, maybe with the fork groove center if the diff opening.

It can go all the way left/passenger side and groove past the left edge of the opening. Not sure exactly what the range should be

 

I don't think it moves much, not much farther than the travel of the fork on the actuator.
I have yet to take any of them apart, everything here is from helping other solve their problems, the testing I did on my truck, and reverse engineering how the system works.

 

Ok yeah I can spin the gear with my finger and the fork moves pretty smoothly all the way over and back.

Im not sure what the issue could have been unless the ADD detection switch and / or the spring was jammed…

Everything seems to be functioning so I guess I’ll just reassemble and try the 4WD again with the ADD plugged in but not back in the diff.

thanks for all the advice

 

The way it sounds something in there was stuck.

 

Welp, put the damn thing back together and it’s still not working. It must be fried…

The ADD detection switch appeared to be working because resistance check showed open when the switch was open and ~1 ohm with the switch closed.

With the ADD assembled I used the battery to cycle it throw its range of motion (12 mm according to the Toyota 4WD trouble shooting guide).

I checked the resistance between pins 1-2 and got 8.8 ohms.

I could not get a resistance reading from pins 1 or 2 to the body ground although the unit is removed… I even wired pin 4 to ground and still couldn’t get a resistance off 1 or 2.

I hot wired it to the battery 1+ 2- (“actuator status connected”) and only got an ohm reading of 1.2 between pins 3-4. 5-4 and 6-4 showed nothing.

Rewired it 1- 2+ and got nothing for 3-4, 5-4 or 6-4.

About this time pins 1-2 stopped responding to switching the pos/neg. I opened it back up and it smelled hot. The motor still runs by hot wiring the terminals but now the resistance I get between 1-2 is 4.8…

Guess I’ll start shopping around for a replacement ADD

 

Wierd that thing looked mint inside.

 

Ok I guess I confirmed it’s not the ADD… got the new unit in less than two days off Amazon, aisin oem replacement and everything.

Plugged it in - STILL BLINKING. The actuator even moved from engaged to disengaged.

Something must be up with the wiring or ECU… I think I might have to take it to the dealer in town and see if they can diagnose it *sigh*

 

Have you checked your voltages again? Maybe we missed something or you had more than one problem.

 

I have not, haven’t had time. Need to drive this thing across the state Friday so I’m getting a little pinched… considering the time I’ve put into it I’ve probably paid for a day for a actual mechanic by now haha

I should check the voltages again. Still getting hung up on how the ADD was reading 0v in 2WD - wouldn’t that be a wiring issue? I swear it read 12v with the ADD unplugged when I checked it on Friday. Saturday I tried the same thing but it was just blinking 4WD and LO with it unplugged that time.

Im not confident in my resistance checks on the unit. I don’t understand the wiring well enough

 

Yea if you can find one that actually knows how to test the system and won't just throw parts at it.

It sure seemed like the actuator was stuck for some reason.

I mean it's fairly simple how the limit switch circuits work, the 4wd ECU sends out 12v on those wires and the switches pull that voltage to ground (0v) when they close.