4wd dropping out???

[budwich]

As a first time ford and 4wd owner, I am not sure what to expect although I am sure from seeing the number of flashing 4wd hi/lo, etc that this isn't working quite right. With the on slaught of winter, I got a chance to activate the 4wd (auto) on my 96 for the first since I bought this past spring. It worked great and was helpful getting off the start at lights and general moving around in the crap they create when they put down salt that turns corners into a slick gumbo. However, it appears that when I get the ex over 60km/h (40ishmph), it drops out of 4wd (ie. light goes out on panel) and then I get the famous flashing (6) 4wd hi/lo stuff and the thing won't re-engage regardless of switch position.... until I turn the truck off and then back on, then it is "normal" again (ie. turn the switch to 4wd auto and everything is fine) until the next time that I get above that speed. I guess my guestion is.... this isn't normal for "control trac" 4wd... right? I don't believe that the previous owner (an older lady) used the 4wd option alot but am not sure. Is this a weak shift motor?

 

[SkanlaxJMO]

Reset the computer(ie: pull the neg. plug for 15-20 min.) mine did the same thing and that fixed it

 

[Aussie Explorer]

Mine was doing the flashing light’s thing, so I checked/ pulled all the fuses disconnected the electrical connections around the T/Case, shift motor ETC and gave them a good spry with electrical contact cleaner. I also gave the Shift motor a couple of soft tap’s with a Hammer plugged it all back together and it been a week and no problems yet, Shifts in and out of 4WD fine.

 

[gijoecam]

It could be a bad connection or a bad signal coming from the speed sensor(s). Check the connections first as the air buffeting underneath it may be enough to wiggle the connection enough to make intermittent contact.

And for the record, the motor has nothing to do with the 2wd-->4auto shift.

Good luck!

-Joe

 

[budwich]

Haven't been able to crawl underneath... I hate winter... what a mess. Anyways, after doing a "ground reset" (ie. removing grd on battery), nothing changed.... it still drops out at around 60kmph. Anyways, my latest test drives appear to indicate that the light turns off (at about 60) and then I get the flashing stuff (which goes away when the truck is turned off and restarted) but that I remain in 4wd auto in terms of driveline. If I turn my selector to 2wd, then 4wd auto is dropped from the drive line (lights will keep flashing periodically) and will not re-engage using switch selection until I do my on/off ignition. If I keep my truck below 60, I can select 4wd on the fly or at stop with no problem. Anyways, at least I know how to get 4wd if I need it in an emergency. Hopefully, the weather will improve enough for me to crawl under and check the speed sensors on the transfer as gijoecam suggested.

 

[gijoecam]

Given that yours is a '96, I suspect that even though it *feels* like you're staying in 4auto, you really aren't. Typically anytime the lights flash, the system is disabled. The feeling that it's still in 4wd is probably because the front axle is still locked-in. If the GEM is still calling for 4wd, but is getting erroneous readings from the speed sensors, it could disable the 4wd without disconnecting the CAD.

Just a hunch.... definately want to find out what it is though. Keep us posted.

-Joe

 

[budwich]

Crawled under the thing briefly today. Unplugged the front sensor connector and sprayed a little cleaner in it. Didn't seemed to help as the problem is still there. My question is do I need to take the whole sensor out and clean what? Do the hall effects die? The rear one was little tougher to get at in the current state of the underside (snow, dirt, wet)... hopefully it will dry up before the end of winter... ya right... One thing that I noticed on the recent "test drive" is that the auto 4w will only engage (ie. lights on dash turn on) with the vehicle at stop... if you are moving and select "auto 4w", the light will not turn on and will eventually do the 6 flash thing. I assume this has got to be the speed sensor. Is there a way to measure them to see if they are bad?

 

[gijoecam]

Crawled under the thing briefly today. Unplugged the front sensor connector and sprayed a little cleaner in it. Didn't seemed to help as the problem is still there. My question is do I need to take the whole sensor out and clean what? Do the hall effects die? The rear one was little tougher to get at in the current state of the underside (snow, dirt, wet)... hopefully it will dry up before the end of winter... ya right... One thing that I noticed on the recent "test drive" is that the auto 4w will only engage (ie. lights on dash turn on) with the vehicle at stop... if you are moving and select "auto 4w", the light will not turn on and will eventually do the 6 flash thing. I assume this has got to be the speed sensor. Is there a way to measure them to see if they are bad?

I'm not a mechanic and I don't play one on TV, but.....


That definately sounds like a bad sensor or for some reason, whatever the tone ring picks up... when you're stopped, it's seeing both shafts stopped. When you click it into four auto, it's seeing both shafts stopped and thinks everything is fine. Then, when you begin moving, the system sees one shaft turning, but not the other, so it engages the 4wd. After a certain time period of trying to make the shaft speeds match by engaging the transfer case, the system figures there's something wrong and starts the lamp flashing. I suspect that if you hooked it up to a diagnostic scanner at the dealership, they'd be able to pin-point the problem in a minute. You've got a 50/50 shot with the sensors, if it's a sensor at all. It may be possible that whatever tone ring generates the signal in the sensor has broken or fallen apart inside the t-case, the sensor and tone ring could have somehow become misaligned, or something else I haven't thought of.

I'm sure there is a check for the sensor.... I can't seem to find it at the moment though...

-Joe