2013 Tacoma TRD won't engage the rear locking diff

A relatively new guy to TRD Tacoma's but, not new to off-roading having grown up on a farm in rural Oklahoma! I am in East Texas now.

I never gave it much thought until the recent rains. After doing some farm chores, I put my Tacoma in reverse with the diff lock on per the dash light and button position. When I tapped the accelerator, all I got was wheel spin on one side in the loose sand with gravel in the "driveway". When I got home, I stopped going up a slight grade during a light rain, made sure I was locked in the rear, stomped the gas, and got a nice spin on the same wheel as before. Basic 4x4 functions as expected in both 4Hi and 4Low.

The ARB air locker in the front works as expected and the rear is what I believe to be factory except for 4.88 gears. I want to make sure I am not overlooking something obvious before I move on to something more drastic and EXPENSIVE.

Front and Rear axles are running 4.88 gears with 35" tires and I have been debating going to 5.13's. I could air lock the rear axle at that time but, I want to keep LSD/ASC performance for normal street use when things are slick during fresh rain lifting roadway oils or when driving in snow or on ice. I have TRD race brakes on it as well and during hard stops on the street, the opposite rear tire to the one that spins in the rain locks up first.

This is suggesting to me that I have a problem in the rear axle. However, there is no noise or other issues in normal use when it isn't raining. MPG hasn't been noticeably affected but, it is low enough I am apt to miss some additional drag in the driveline that isn't really significant.

TIA,
Sid

 

So, ARB in front, and factory e-locker in the rear correct?
Are you in 2WD or 4?

 

Were you in 4lo?

 

Yep, that’s what I was leading up to.

 

This

The 4WD ECU will only allow the locker to engage when in 4WD Lo.

 

Doesn't the rear locker need encouragement if not used frequently, like the 4wd actuators?

 

More so some back and forth movement to get the splines lined up, regardless of use frequency

 

I was getting frustrated with my 2011 OR until I learned on here to do slight figure-8 turns while rolling forward

And yes you need to be in 4lo

 

Yes. It needs to be used semi-frequently.
The actuator is still gear driven with contact traces and limit switches.


Where as the 3rd gen is magnetic activated. It can get by longer with out frequent use.

 

2 wheel drive

 

Sounds like I need to retry this in 4Lo and rock back and forth to see if things line up and engage.

 

Sounds like as a newbie, I need to learn a few things! I'll give this a try soon.

 

HUGE THANKS to everyone! With the lights on the dash, I was expecting it to work. Learned something new today!