2011 4H won't engage anymore

Do you see the link in my sig. below? It is all there... But, I want to help and sometimes a personal answer beats a web site or something I wrote almost 2 years ago...

A-TRAC is Active Traction Control... and any traction control is a slip limiter, because if a tire slips, you don't move very well. 4WD helps because it puts power up front, but if one of those tires slips, then you are not moving... Just one tire in front and one in the rear will spin, and the other does nothing... you are stuck.

TRAC (traction control) or Limited Slip Differentials apply friction to a slipping tire using the brakes or clutches inside the diff. to slow down the spin so power can be shared over to the traction tire on that axle.

This is not always enough, specially off road. A-TRAC is best described as automatic locking differentials... as soon as a tire slips, its rotation is slowed to match the tire with traction... so power is split nearly 50-50 across the axle... much more so than TRAC or limited slip shares the power.

Now, the purist 4WDers love lockers, as it is 100% locked left and right tires... and the Off Road Tacoma has a locker on the rear axle.

A-TRAC works on the front and rear axles, and because it only 'locks' at the moments you loose traction and not all the time, steering the truck is not difficult or has any stress. Lockers, specially a front locker makes turning on firm ground very hard, and requires unlocking so the tires can rotate at different speed.

It is this 'automatic locking and unlocking' that some may not like about A-TRAC, as it does make some big noises, and it can be a bit jerky or allow some slip before it activates again. However, it works and it comes with our trucks and for that, it should be praised. It was available on other Toyota and Lexus 4WDs long before it was added on the Tacoma... So, it is a proven traction system. With just one tire on firm ground (a front tire even), and on a slope... uphill even... A-TRAC will pull you out... a rear locker would have done nothing if both rear tires are off the ground.