Rear Diff Lock Anytime Mod 3rd Gen DEVELOPMENT

Does the display indicator tie into the ECU? It would be great if we could just bypass everything and make it a completely dumb system feeding it the correct voltage to lock, but I’m certain it’s not that simple.

 

The lock feedback switch in the diff does feed into the 4wd ecu, which processes the data and sends the indications to the dash display over CANBUS, which then displays the dash display indicator.

It does this so the ECU can monitor the lock feedback and throw codes if the lock doesn't lock when commanded or doesnt unlock when commanded.

Manually driving the lock coil is pretty easy. Just disconnecting the feedback switch so you dont get a dash indication is very easy. Making the dash display the lock signal without causing the truck to throw codes is relatively very hard. Making your own lock light using the feedback switch is pretty easy.

 

whatever is easiest. i can do a whole separate switch or i seen your posts earlier in the thread with a setup using factory switch with that iec255 relay. i have no trouble cutting and splicing factory wiring just not familiar with all these little technical electrical doodads.

 

The absolute 'easiest' for most is to use a separate switch, but easy for one person may be hard for another. Just remember if you have no safeguards in this system when locking the rear, if your kid borrows your truck and locks the rear locker on the highway, it may not be good. So a guarded switch or some other 2-step locking procedure is probably recommended.
(Probably the 'easiest' is an aftermarket 'normal' latching switch installed in place of the original lock switch, and bag tag and secure the OEM locker switch.)
***If you want to use the existing overhead momentary OEM locker switch, then you will need a latching relay like this

$11 HiLetgo 2pcs 12V Single Bistable Self-Locking Relay Module Push to Start and Stop

https://www.amazon.com/HiLetgo-Single-Bistable-Self-Locking-Module/dp/B01HHM5M4M/***

If your switch isn't capable of at least 5 amps DC (or you don't want to run larger wire to where the lock switch is located), I would wire the switch to control a normal automotive relay, and use that to drive the lock coil.

After that decision, then you have to decide if you want any indications that the locker is powered and also if any indication that the locker is locked... Attempts to use the OEM locker indication in the dash will result in thrown codes, however the feedback switch in the rear diff can be used for aftermarket locking lights. If an aftermarket switch was used, then that can be used for the locker-power indication typically. This is optional, but at a minimum the OEM lock feedback switch must be disconnected from the ECU

I recommend adding a resistor to the locker power wire, to reduce the voltage into the locker coil to not exceed the values that Toyota used. (Coil might be fine for the full 14v, but why risk it). I have been recommending a 1.5 ohm 100W resistor (or 2* 3ohm resistors 100W in parallel), that MUST be attached to a heat sink of some kind, like a piece of aluminum or the vehicle frame, etc.

I also highly recommend a flyback diode across the lock coil (downstream of the relay or switch). This is important to protect the switch or relay from being burned by the large inductive current caused by the lock coil when shutting it off. Just about any stout 5 amp diode will do, although I usually recommend something like a 5-10amp rectifier diode just because the bigger leads are a little more stout.

The 4wd ECU should have a 3 ohm resistor (any power size) attached to the ECU side of the wiring, so that the ECU thinks the locker is still attached. Make sure the OEM locking switch is disconnected from teh ECU to prevent this resistor being overheated. Make sure this connection can't leak current to ground (due to water, etc), as this will throw codes.

How you wire this stuff together really depends on what you feel most comfortable with... if you prefer just cutting the OEM harness and solder-sleeving, or if you want OEM connectors, or if you have 2wheel-low harness and want to splice in there are all fine solutions...

Take a look at the 'schematic' posted in the first post in @fuzzydoodle post (which describes his work in installing an OR rear axle in his sport and hooked up the locker)
Factory locker install on 16 sport | Tacoma World

 

@BigWhiteTRD and others seem to know a great deal about our Diffs, so I ask:
It seems the diff is activated and kept activated by a lesser varying pulse width voltage from the 4WD ECU to the diff "solenoid" (not a motor like in the transfer case), upon deactivation a spring within the Diff returns the mechanism and shifting fork to the open diff position. If my assumptions of the "spring" and "solenoid" are incorrect I need to be corrected.

What about removing the spring and replacing the solenoid with a motor that moves the shift fork? Much like the transfer case has a motor that the polarity of the voltage is reversed to engage and disengage the shift fork. This would make the electronics easy in my way of thinking and there would be no worry about how much voltage to apply to keep the locker engaged.

I don't know where the spring is located, on the electromechanical shift mechanism or deep within the Diff? With an ARB, which I am familiar with, the springs to return the Diff to the unlocked position are indeed deep within the locker.

Also, one unrelated question. What happens in the stock mode when I stall the vehicle on a very tough obstacle and I absent mindedly in my stress turn off the ignition, does the Diff lock disengage and my truck rolls a bit or more depending upon my predicament?

To confuse matters more, I have heard that if my electronics fail on the trail, I just need to remove the shifting mechanism and physically move the shift fork, but would it stay in whatever position I move it too?

Thanks for any enlightenment.

 

There is no shift fork and it is a pretty well integrated unit (kind of similar in layout to ARB). It's basically a dog clutch that is part of the armature (plunger). When you energize the coil it moves the armature/dog ring into engagement overcoming the return spring. Without being energized (like when the ignition is off) the return spring will be trying to disengage the clutch. It won't necessarily disengage if the dogs are in contact and under enough load. The load would also need to be relieved so the return spring can return it to the unlocked state.

People get hung up on the pwm but it's nothing more than applying a constant voltage that's lower than the source (12V) voltage that's available to the solenoid driver circuit. Just put the constant voltage on it, trick the ecu into not knowing it's locked, and you're good to go.

Below is a good look at the locker.
https://www.tacomaworld.com/threads/stock-8-75-bd22an-locker-dissection.674592/

 

Thanks for the clarifications, in all respects.

So, on a trail failure of the electronics the only thing to do is to wire in a 12VDC supply to the solenoid, hoping it was not the solenoid that failed. There is no way to manually activate the locker! Spring is not accessible, solenoid is not field replaceable, so it is sounding more like the ARB in field serviceability.

I'm still trying to wrap my head around the picture and component drawing of the thread link you supplied. I wish there was something like this for the Toyota locker:

https://www.rocky-road.com/media/ARBairlocker.gif

 

Yes, you'd need to put power to the solenoid. Whether the 12V is long term safe is not known for sure. We know the truck applies about 10V to get the locker engaged and drops to about 6V to maintain engagement.

Solenoids rarely fail, it's just a bunch of wound wire. Chances are a failure will be a busted harness/connector or an internal mechanical failure where manual engagement wouldn't do anything anyway. The solenoid actuator itself is probably the most reliable and robust part of the system and miles better than the old motor, gear, rack, wipers, shift fork nonsense.

I think that ARB animation is their older style. The newer version is a much cleaner design.

 

Thanks for the realist approach. I have seen the current ARB website and the different approach they have taken with lockers. My Samurai has the old style, wonder if they redesigned those models into the newer versions? I will be finding out soon as I believe my spider gears are shot (in the Samurai), will find out before summer when I get into the third member to see.

 

In full disclosure (and not recommended) there *is* a way to manually lock the locker. This was discovered by a member here by accident. The diff lock indicator switch that goes in the side of the 3rd member "hooks" on the other side of the differential lock position plate. This plate moves with the plunger and when it moves to the locked position it pulls the indicator switch out to indicate the locked state. If you can take this indicator switch out (be careful it doesn't want to come out because it's hooked around the position plate and is designed to be removed after the carrier is removed from the 3rd member) and then insert it or something else back in that pushes the position plate in, it will lock the diff. Know that the position plate isn't there to be pushed on to lock the diff and whatever impinges on it will be rubbing and squealing as the position plate rotates with the diff.

You asked, that's a way.

 

Bravo
Way to convert an 'Issue' into a 'Feature'

 

Looks like I need to go under and explore.

 

doing things. waiting on switch and another resistor.

 

just seen this posted 2 hours ago on facebook. clean plug and play solution using the factory switch. also has a failsafe that the lock button has to be held 3 seconds to lock to prevent accidentally engaging it.

https://experimentalinc.com/products/anytime-locker

 

TBQH, after driving my 2020 OR on a multitude of terrain I think an any-time A-TRAC/MTS would be more useful than an any-time rear locker. Albeit, I don’t think I need either. I’m confused by this popularity in using the rear locker at hiway speeds. When the get any where near a location where I might need my locker, my first action is to put the truck into 4lo.

I have found very few situations where a-TRAC plus rear locker is better than a-trac alone.

The advantage of a-trac is that it doesn’t mess with your steering like a locker does and this is extra important at hiway speeds.

 

nobody is using locker at highway speeds. not sure where anybody even said that.

and its actually least important at highway speed because theres very little difference in wheel speed. i can say from personal experience its completely un noticeable with a spool when up to speed.

 

2hi and 4hi are for hiway speeds. In a situation where I think I need my locker, I’m going no more that 5mph.

 

I had an any time locker on my 3rd Gen 4Runner and I had a blast using it on the trails in 2-Hi and 4-Hi. I did most the trails in Ouray/Telluride in 2-Hi and my rear locker on. I did it just see how far I could take it without going into a 4-Hi/Lo.

 

2hi locked can get you through alot of stuff youd usually need 4x4 without the drivetrain bind. but most of all being able to have the rear end of truck slide when on sand or fire roads is much more fun. its not a use it every day thing. i just want to be able to use the locker freely without a stupid computer telling me i cant