Rear Diff Lock not engaging, Rear Lock Light just flashes

[patrick28x]

Hi all,

I have a Gen 3 and the rear diff lock has never engaged since I got it. The person I bought it from told me that it was always finicky and that "It worked last time he drove it" but I am not sure it that's true.

I've researched a lot, watched many videod and have tried many solutions. Here's what I've done so far.

To start, I put the truck in 4H. I then put truck in Neutral. I then go from 4H to 4L, then put truck in drive and start moving slowly (Under 5mph) and then press the Rear Diff Lock button, The ABS light comes on which is good and the Rear lock light just flashes showing its trying to engage but has not yet. I keep moving, coming to a stop, try turning a bit left to right. Trying backing up then forward but still no engagement.

I try other sequences like put the truck in N, the 4L, then into Drive then push diff lock button before moving. Still no engagement. I even tried having it in 4L and in Neutral and tried to engage.

Next I unplugged all the connectors to the Diff and diff lock. Cleaned them with electrical cleaner and plugged them all back in. Pins and connections all looked good. Still no engagement.

At this point I feel I tried all the self remedies. Can anyone help point me in the right direction non what to do to diagnose this or to fins out where the problem lies. What part should I replace or test? Do I need a new actuator or what? I dont mind just buying a replacement part if i just knew what to try or perhaps someone knows what the problem part may be

Any help or suggestions is appreciated.

Thanks

Patrick

 

[5VZ-FE]

It sounds like your issue probably lies inside of the locker itself, maybe the actuator. This YouTube video shows how to rebuild the actuator, and even if that isn't your issue it has some great info, and shows exactly how the locker works.

https://www.youtube.com/watch?v=aqPmA0J0Zco

 

[DAW89446]

Before I got my ‘18 T4R, I had a 2002 Tacoma TRD 5-sp.

Probably the same rear end set up. They can be a bit finicky but your’s sounds like it’s not working. Or you’re not giving it enough time and distance for it to finally engage if it’s sticky.

In the first years I’ve owned the truck, I only engaged it before I would tackle a technical section; but later started engaging it any time I started a trail where I knew it would come in handy at some point, leaving it on for miles. At times, engaging it the light would flash for a tenth of a mile or more until it would suddenly engage when one of the rear wheels would break loose.

I’ve never pulled mine apart, but the actuator looks easy to get to. My truck even had a little skid shoe covering the actuator.

 

[patrick28x]

DAW89446
Are you in 4Lo when you get on the trail and start driving. When you drive that longer distance are you going over 5MPH? What speed do you think is ok to drive for a while? DO you have your shifter in D in lower speed like 2?

 

[JohnMc]

It sounds like your issue probably lies inside of the locker itself, maybe the actuator. This YouTube video shows how to rebuild the actuator, and even if that isn't your issue it has some great info, and shows exactly how the locker works.

How To Rebuild A Toyota Tacoma E-Locker Diff Lock Actuator - YouTube

/\ /\ /\ This would be the issue with all you've tried. I guess one last chance you could give it would be to jack up both back wheels, push the button (key on, motor off) and listen for a little electrical motor whirring briefly. The motor just runs and preloads a spring, the spring then waits patiently for the locking collar to have a chance to engage. So push the button, then rotate one of the wheels - the other wheel should rotate the other direction (open diff). If it never *clunks* into locked, then plan on taking off that actuator and taking it apart to see what's wrong with it.

You need to be *VERY* careful pulling that actuator off. Especially here in the salt/rust belt, it can really be stuck on. Aluminum housing against cast iron, not a good mix when there's salt around. I was super SUPER careful with mine, and I still cracked the aluminum back plate on the actuator. It's pretty fragile. Luckily enough, you can still use it with some modest cracking.

Inside you might find hardened solidified grease, rust, gunk, separated magnets on the motor cover, etc. It's usually worth taking apart to see if you can fidget it back into functionality since new replacements are 350 to 500 bucks (or 1000 from the dealer, lol).

 

[DAW89446]

DAW89446
Are you in 4Lo when you get on the trail and start driving. When you drive that longer distance are you going over 5MPH? What speed do you think is ok to drive for a while? DO you have your shifter in D in lower speed like 2?

Trails I left the locker engaged were much like shown in the photo above. I lived in an area that was full of such trails and I drove them repeatedly. That trail is much like shown in the photo for about 25 miles and speeds under 20 mph. Driving for miles with the locker engaged didn’t seem to hurt the truck; though you could hear and feel the rear tires being drug through turns since they both turn the same speed. My son, who lives out of state, still owns the truck and uses it off road. It has well over 200k miles on it now with no drivetrain failures whatsoever.

The Tacoma had a manual transmission.

Otherwise, I generally left my truck in 4LO and used the higher gears if conditions permitted speeds up to about 25 mph. If on smoother dirt roads, I used 4HI.

I pretty much practice the same off road habits driving my T4R. It’s an SR5 so no rear locker any longer. When on dirt roads I generally run in 4HI just to keep the shifting mechanisms and drivetrain limber. On two track trails and worse I’m in 4LO. I am not a fast driver off road, so yes, my transmission is generally locked in D2; in D1 on long downhill sections (I dislike that DAC button - too much drama).

 

[96RedRunner]

Jack up both back wheels, push the button (key on, motor off) and listen for a little electrical motor whirring briefly.

You be at Diff locker have someone else pushing button. If you hear motor run and stop tap on actuator with small hammer while rotating a tire.
If you decide to pull it start spraying it with penetrant every day a week before you try.

 

[MountainBrew]

I tried diagnosing the same issue for quite a while, light never stayed on solid and I assumed the diff wasn't engaging...only to discover it absolutely was engaging and the light just wouldn't stay solid. May be worth throwing it up on jack stands and giving it a try. Could save you a lot of headache.

 

[patrick28x]

Thank you for all the replies. I will start spraying some Kroil on the housing and Actuator to begin penetrating to loosen it up in preparation for removal (Great tip 96RedRunner)

I have ordered a floor jack and stands, should be here this week. I will then Jack up both wheels and try the tests mentioned. Thanks JohnMC

Lastly I have found a new part Diff Locker Actuator PT# SAT-009

If all else fails I will order and install the new actuator.

Thank you for all the feedback and help. Feel free to share any other ideas. I will post up results once done