Factory front locker won't turn off (1 Viewer)

[jpoole]

Hello All,

The factory front diff lock on my '97 will not turn off or disengage while plugged in at the axle end. If I disconnect the two plugs on the front axle that are in the locker area then the front locker disengages and the dash light goes out. If those two plugs are connected the dash light never goes off and the front locker remains engaged including light front tire squealing when turning on pavement. Shifting the transfer from high or low has no impact on the front diff locker engagement that I can tell.

The locking knob works properly for the rear diff locker including only engaging the rear after the transfer is shifted to low range and after a bit of blinking. Turning the locker switch and shifting the transfer case seem to have no impact on the front locker which remains engaged with a solid light on the dash.

I'll get into the FSM and troubleshooting soon but wanted to find out if there are any obvious places to start on this issue. For now I've disconnected the two sockets on the front axle to avoid damage to the front end while driving on pavement.

Thanks,

 

[mudgudgeon]

It does not make sense that the locker would disengage AFTER being unplugged. The actuator is a motor that drives a worn drive to shift the locker gear in both directions

The plug on the actuator has two wires connected to a switch that is activated when the locker is in the LOCKED position. Unplugging the harness breaks the circuit to the dash light, which is why the light goes out.
The remaining wires are for the motor. Ground, motor IN, motor OUT. without power the actuator won't move.

I'd possible you have a faulty LOCKED indicator switch that stays ON.
Have you verified that the front is actually locked? Eg jack up one front wheel and see if you can rotate that tyre.
If the CDL is locked, you'll get driveline wind up on a hard surface which will account for light squealing, some shuddering, and difficult steering at the front wheel while turning.
If the front was locked, you would need arms like Popeye to drive it around corners on a paved surface.

It can take a bit to get the front locker to disengage normally, as if you have any load on the front driveline, the locking gear will bind. It may take some rolling back and forth several yards (up to 50ish) with light steering left and right to get it to unload, particularly if on a high traction surface.

 

[jpoole]

Thanks mudgudgeon,

What you are saying makes a lot more sense than my conclusion since I was assuming some sort of auto-retraction when the locker was de-powered. It's really helpful to know that both engagement and disengagement are motor/gear driven.

I've barely driven this truck since buying it and given your description have misdiagnosed the front locker issue(s) that it may have. When I got the truck the front locker was unplugged at the axle (indicating past issues I assume) but the truck drove fine, like there was no issue with the front being engaged and stuck. I never fully tested the front locker at that time. The truck has been sitting for more than a year until today so I'm just getting around to testing some of this out better. Hopefully it will operate in a sensible way when I test again later today. I'll report back with better information once I have it.

 

[dcguillory]

Rebuilding the locker actuater is not a big deal since you have to take anything off to get to it.

 

[LandCruiserPhil]

Like others have said if it is "locked" unpluging will do nothing to change that. If it is "locked" you can open the cover to access the bolt that secures the shifting fork to the actuator shaft, remove the bolt and manually slide the fork over and 'unlock" the dif. If this is the case the actuator needs to be repaired/replaced but you are now "unlocked".

 

[jpoole]

As I suspected after learning from mudgudgeon I was wrong with my initial assessment. The front locker was not engaged and the tire chirping must have been when I was in low range and the center diff was locked as I tried to get the front diff to respond.

After driving around in a gravel lot a little while ago I've determined that the rear locker works correctly but I never noticed anything different in the front axle. I assume that it would be really obvious when the front engaged so it seems like I've got an unlocked and non actuating front locker.

Now that both plugs on the front axle are plugged back in the front locker indicator is always on solid. It doesn't blink regardless of transfer case position or locker knob position.

Any clues on where to start with this? Pull the front actuator out and clean it up? Test wiring? Of course I can search here and look in the FSM but after many many hours reinstalling the head and misc engine components I'm feeling lazy and appreciate any clues.

Thanks,

 

[Tools R Us]

As I suspected after learning from mudgudgeon I was wrong with my initial assessment. The front locker was not engaged and the tire chirping must have been when I was in low range and the center diff was locked as I tried to get the front diff to respond. ...

Yep, if the front were locked, you would know it, steering becomes difficult, more so on pavement. For testing I prefer to jack the axle up, that way you can turn the wheels and see what is going on. When a locker is selected, should hear the relay click, inside, right kick panel, then the actuator motor on the axle briefly run, slightly turn a wheel and lock. What is working and not?

 

[LINUS]

I remember the rear position switch & the NAPA pn# for a ~$20 one, not 100% that the rear & front indicators are interchangeable (anybody want to confirm from memory?)

If you can interchange, I'd try that after you jack up one wheel up front, confirm position & run the locker switch, then go out & spin the tire 'till the locker kicks in (easily may take a few full revolutions) - then check your dash indicator.

It could be a short in the socket, a worn wire in the harness - or that position switch.

If the locker actuator is found to be stuck, you can maybe 'jumpstart' it loose with a 9v battery, sort of acts like tapping it with a hammer.

 

[ppc]

The fact the light goes off when the harness is disconnected tells me the wiring is not the problem. I would remove the indicator switch and test continuity with a meter. Sometimes just exercising the switch 50 times or more while spraying with WD40 or BrakeClean can bring the switch back to life. If not replace it. As previously stated there is a aftermarket solution for ~$20 at your local auto parts store.

 

[Tools R Us]

The fact the light goes off when the harness is disconnected tells me the wiring is not the problem. I would remove the indicator switch and test continuity with a meter. Sometimes just exercising the switch 50 times or more while spraying with WD40 or BrakeClean can bring the switch back to life. If not replace it. As previously stated there is a aftermarket solution for ~$20 at your local auto parts store.

The light, switch, associated wiring, has nothing to do with the locker operation, it only reports lock confirmation. For diagnosing locker problems, best to ignore it, once the locker is working, then worry about the light, or not.

 

[ppc]

The light, switch, associated wiring, has nothing to do with the locker operation, it only reports lock confirmation. For diagnosing locker problems, best to ignore it, once the locker is working, then worry about the light, or not.

I have to disagree. There is an obvious problem with the indicator that will eventually have to be repaired. With the OP not being completely familiar with the operation of the lockers the visual feedback will be helpful. With the indicator light fixed, when the locker is enabled the light should flash until the lock is complete. If the light doesn't flash that would point to a potential problem with the locker ECU. If the light flashes then it would point to a problem with the actuator. In any case the indicator fix is relatively simple, no or low cost, less time consuming and helps the OP learn how the system functions.

 

[Tools R Us]

I have to disagree. There is an obvious problem with the indicator that will eventually have to be repaired. With the OP not being completely familiar with the operation of the lockers the visual feedback will be helpful. With the indicator light fixed, when the locker is enabled the light should flash until the lock is complete. If the light doesn't flash that would point to a potential problem with the locker ECU. If the light flashes then it would point to a problem with the actuator. In any case the indicator fix is relatively simple, no or low cost, less time consuming and helps the OP learn how the system functions.

Whatever, doesn't change the fact that the light circuit has nothing to do with the operation or diagnosis of the locker.

IMHO, the lights are one of the Toyota design fails, give too much information, would be much better if the light simply came on when switched, like the rest of the lockers in the world. Have seen way too many examples where people fixate on the silly lights, when they should be concentrating on the obstacle, driving. My advice to new '80 wheelers is to ignore the stupid lights, if lockers are working, will lock when needed. After a couple of lock/unlock events, if you cant tell that they are on or off by driving feel, you have no business holding a steering wheel!

 

[jpoole]

Thanks for the additional info,

It is really helpful to learn that the indicator light is independent of the locker mechanism and at the same time that piece of into increases the importance of troubleshooting the locker itself. That's my attempt at saying both @Tools R Us and @ppc are right

I will be doing some general inspection this weekend to familiarize myself with the locker and indicator light on my truck. Hopefully something obvious will show up. If not, I'll be better able to understand what I read on here and in the FSM as I get into troubleshooting and repair.

My current guess is that both the front locker and the indicator switch are full of crud and suffering general neglect (like the rest of the truck). Hopefully all wiring and the locker ECU are fine.

 

[KLF]

I would pull the actuator and see if the toothed rack is movable with a screwdriver, it's only 2 nuts and one bolt. Put the front up on stands so you can get the axle in slack to make it easier to move it. It's probably time to rebuild it anyway, at least pull the cover off the back and look at the drive gear, make sure there's no crud in there.

Front & rear "locked" switches are the same, so you can swap them to diagnose.

 

[mudgudgeon]

I'd start with jacking up the front end. Test the locker. if you have someone flip the switch for you ,you should hear the actuator motor whir a little. Rotate one front wheel to see if it locks. It will put out a fairly solid "click" when it locks in.
if yu dont hear the actuator motor, verify that you are getting 12volts to the actuator when the dash switch is rotated to lock, and again (different wire) when the switch is shifted from the locked position.

If its not actuating, and you have 12volts ,pull the entire actuator, strip it and clean it up. test it on the bench, refit

its simple enough to remove, if in doubt follow the FSM, or find a how to thread here

 

[jpoole]

No time to dig into the locker components on the front axle today but I did just go out and shift the transfer to low and then rotate the locker switch to rear then front without the engine running so that I could listen for clues.

Heard:
-a center diff lock type noise when I shifted into low range
-the rear locker relay in the passenger floor area then the rear locker whirr when I selected the rear locker
-the front locker relay click and the front locker whirr

I'm optimistic that my only problem could be the locker indicator switch being stuck on and a bit of impatience or bad testing of the front locker to date. Seems like the indicator light wiring is ok since the light goes out when I unplug it and seems like the switches/relays/wiring/ecu are all ok since I heard the relays click and the lockers whirr when expected. I'll test the front with a wheel up tomorrow to see if it will engage and then pull the front indicator to see if it will work with cleaning.

In the long run I plan to clean/regrease/reseal both locking mechanisms but at this point I'm still just trying to figure out what's broken on the truck, and how badly broken it is as I move through initial baselining. After doing a head gasket job including lots of resealing and hose replacement it's running great and passed emissions today so now I can move on to the rest of the truck...

Thanks again.

 

[Brimley]

Don't you love this cite!. Sounds like you need a $20 dollar part. But if not you tried that first!!!

 

[-Spike-]

You will need more than one tire lifted to test locker operation. With the CDL engaged and 3 tires on the ground, the fourth shouldn't turn freely, regardless of axle locker position. Best to lift at least one tire on each axle, then tires both will rotate with CDL engaged and axle locker disengaged, will not rotate with axle locker engaged.

 

[jpoole]

I did some investigating today and have some updates though I'm sure they'll contain incorrect names for some of the components involved, sorry.

After lifting the front passenger/right side tire off the ground I tested the lockers by first shifting the transfer to low and then spinning the locker knob to the front and rear locked position. I spun the front right wheel in both directions and didn't get a click or a lock.

From there I pulled the locker engagement indicator switch and hooked it up to an ohm tester and found it to give unreliable readings as I moved the plunger in and out. After working brake cleaner into the switch and exercising it for a while it started to give consistent readings and I believe that it's now functioning correctly. After reinstalling the indicator switch the front diff light was still on solid regardless of my shifting of the transfer or spinning the locker knob.

I then pulled the motor/gear/whatever off of the axle and the cap that covers the end of the actuator rod (right name?). Once I had these two items off I could easily move the actuator rod in and out by hand. It had been in the "in" position without any length of the actuator rod sticking out into where the cover had been. I tried reinstalling the motor after moving the locker switch with the motor off in case it was out of phase with the actuator rod or something like that but didn't get any different behavior (I may have done that incorrectly?).

In the end (time ran short) I manually moved the rod to the "out" position where it was protruding into the cap. I then reinstalled the motor and actuator rod cap and now do not have a constant light on my dash for the front locker which is nice.

When I spin the locker switch to engage the lockers I now get two blinking lights on the dash. If I were to drive around the rear would engage.

I spun the front right tire forwards and backwards with the actuator rod fully in and fully out (moved by hand) and never got a click or a lock of the front wheel.

While exploring I discovered signs that the front-end has been apart on my truck. I'm starting to suspect that I have bigger issues in the front axle than the locker. As stated by -Spike- it seems like my front-right tire shouldn't have been spinning freely with the front-left still on the ground. I'm going to read up on things and get a better idea of how to test for bigger issues in the 4wd and front-end on this truck. The truck drives fine and doesn't make noise etc. in the drivetrain but I don't know if AWD or 4WD are functional of not as I've only driven on pavement a limited amount. Getting both front tires off the ground seems like a good next step for testing but any other suggestions are appreciated.

Thanks

 

[mudgudgeon]

As stated by -Spike- it seems like my front-right tire shouldn't have been spinning freely with the front-left still on the ground.

Correct, unless the transfer is in neutral. With the transfer in gear, and one wheel lifted, you won't be able to rotate the lifted wheel.
Locker control circuits only work with the transfer in low, unless you have a CDL switch on the dash and have it on

Did you bench test the actuator motor? I.e., put 12volts through it.

If you manually shifted the locker, you may need to do this while slowly rotating one tire.
The locking ring has very coarse teeth with square shoulders (6 teeth) you need to rotate the tire far enough to let these align while applying some force to the locker mechanism