Originally Posted by white89gt

It does for the Auto 4WD. It uses the ABS sensors to sense "slipping" and activate/deactivate 4WD.

Originally Posted by ddgts68

The f150 does have the solenoids. The expy does not..

Originally Posted by akdoggie

97 and up Expeditons had the option of AWD (Control Trac). It nothing special, just a selection where is can be AWD when necessary.

The front differential is actuated by a vacuum pod that operated a fork inside the right front side axle tube. The pod is operated by vacuum from 2 solenoids on the right side firewall below the power box. One side is on the other is off. There are 2 plastic lines that can crack, if so you take small hose and use it to attach the two pieces together until you can make up a new line. The 4 position switch on the dash is AWD all the way to the left. When it is engaged, or 4H, the solenoid will work the pod to engage the fork. When you go to 2wd it pulls the fork back and disengages the front differential.

I'm confused. You said that the OP pulled the front Driveline for ABS reasons? ABS is separate. There are sensors on all 4 wheels with Control Trac. The drive line is just a rotating piece of metal. Reinstall the drive line and check it out.

Originally Posted by jethat

My F150 has 2 vacuum actuator solenoids next to the firewall relay. When I bought the truck 4wd didnt work because a little battery acid had dripped on one of the vacuum lines. I patched it and they have worked since but its probable a similar set up.

Originally Posted by ddgts68

Well I got the front shaft in, had it up on jacks, ran it, and front diff kicked in about 10 mph. Made a lot of noise kicking in and out, guessing because of no load. Have a slight vibration on deceleration though and steering feels heavy? Got to find some dirt now!