I doubt the computer gets involved, mechanical sensing, would be another of my guesses. Most of these systems are pretty simple except for high end cars. Mechanical systems either sense a torque differential from the wheels and add power or are in FWD and allow slip between front and rear.

 

It uses the wheel speed sensors to notice slippage. My limited has the auto setting and it does work well. But its no different then the auto setting in my '98 Expedition. The rear has to break traction before the front engages.

 

Yes, mechanical systems are fairly crude but still serve a purpose regardless. The new 150's may be more sophisticated than a mechanical system but I'll bet a buck the current systems are the same as your 98' Exp.

 

No need to bet, I agree with you. Back then they called it "control trac" but both trucks act the same. The older Explorers (1995-up) and Expeditions used wheel speed sensors to detect slip and kick the t-case into 4 high, the same as the new f-150s.

'98-01 V8 Explorer's use a fully mechanical AWD t-case and it actually works much better providing 35/65 % TQ split front/rear but can give up to 50/50 if needed. Its a very smooth system with no clunks or jerks that come along with the Auto 4 wheel.

 

I miss the good 'ole days of manual hubs and a tcase shift lever...,but I do love my new FX4 and I can see the auto feature being nice, especially in winter weather conditions.

Subbing to see where this goes.