ddgts68

Trying o find info on control trac. Didn't know if any of this gen came with it. This forum seems to be the go to place for me to find info on wife's 99 expedition xlt, 5.4l, 4wd. The exp forum keeps telling me I have vacuum modulator like my 97 f150 4wd to engage front diff. Just trying to figure how it works. PO remove front drive shaft because of bad abs sensor. What I have read says the transfer case uses the front drive shaft to determine weather power applied to front. If so has the transfer case been engaging itself since no drive shaft? Once again thanks for all your help!!

OhioLariat

Control Trac wasn't offered on the F150, so the Expy forums will likely be your best source of information; however, there are a few folks on here that just might be able to weigh in.

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.

ddgts68

Thanks OL I was hoping someone might as the expy forum has been very little help.
Thanks AK I do not have the vacuum pod or solenoids. The switch on the dash only has 3 positions being A4WD, 4H, 4L. The PO had abs sensor go bad on RF, and the shop she went to took front drive shaft out! Said 4wd drive engaged all the time. I am more curious on how it works, would like some basic understanding of how things work.

OhioLariat

AK is one of the people I figured would pop out with valuable info.

It sounds like that "mechanic" didn't know what he was talking about. ABS would have nothing to do with activating the 4WD system. Removing the drive shaft and other components was probably a band-aid fix for the 4WD system acting up. Too bad they yanked parts off rather than actually fixing it.

white89gt

Yeah... my Expy has the A4WD, and I still have the solenoids. Are you sure you don't have them? They are mounted on the firewall behind the battery.

ddgts68

I agree AK, it was a tire shop that they took it to.
I just looked White and there is no solenoids, wires, vacuum tubes, etc. I looked at my 97 f150 to make sure and there is nothing!

white89gt

You're saying your F150 does or does not have the solenoids? Sorry.... just clarifying.

white89gt

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

ddgts68

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