Intermittent 4x4 Issues

Every now and then I will try to engage my 4HI and the 4x4 light will continue to blink and not engage. Even after shutting the truck off and back on it will not work. It will only start working and engage properly when I either disconnect the battery, or pull the fuse in the cab labeled 4WD. Where should I start looking to diagnose this issues?

 

what year is this? If it is still under warranty, take it to Toyota. if not, try to go forward, then reverse a few times and see if that works.

 

It's a 2008, no warranty. And I tried that, when it stops working nothing will get it to engage except disconnecting battery or pulling fuse.

 

are you slowly rolling when going from 4lo to 4hi with the wheels straight? my 2013 is very sensitive to any binding in the drive train and will only engage after "rocking" the truck to allow the gears to mesh.

 

Very likely the ADD on the front differential. If the front drive shaft spins, it's the diff.

Typically to diag it I use a known good, or I'll remove it (4 12mm bolts) and see if it moves back and forth when trying to actuate the 4x4.

I've changed probably 100 ADD's and maybe 2 transfercases in my career.

It's a very simple system with very little computing involved.


This video shows him testing both units and you get an idea.

 

This guy right here took the words out of my mouth. It is very simple fix if it is the front ADD. If it is the Transfercase ADD, it is super expensive and not something you should try at home.

 

It wont engage in either 4LO or 4HI, when i switch from 2hi to 4hi it stops working

Thank you! I searched and couldnt find that. Will be at shop today and will see if boss lets me bring it in