Hi everyone.

I have read most of the previuous postings regarding this issue, but still have some questions. The "4X4" dash light does NOT come on also. I was told by Ford, that if the light does not come one, it could be transfer case motor. A local garage told me that my 4X4 probably wasn't engaging because I needed a Front Differential Vacuum Motor. I put one in. No luck. I was told that the axle goes in but the lock/unlock wasn't working, thereby possibly eliminating a transfer case motor problem. I'm in the process of ordering new solenoids (Lock/Unlock 4X4). I was told they are about $70. One has come in so far, the other is back ordered. In the meantime, I was thinking of replacing the vacuum lines between the solenoids and the front differential vacuum motor, because I thought that might be cheaper than solenoids, but the dealer told be that the vacuum lines are $128, and that would get me the top half, and I would need to spend another $128 for the bottom half. Does this sound right????

There are two lines that run off of the vacuum motor, one is like a small radiator hose that stops near the passenger wheel well with nothing connected to it. The other line is a black plastic tube that has one pink, and one blue vacuum line inside it, those run up to about where the previously mentioned hose ends, where it connects (plugs) into another harness that has similar colored lines that run up to the solenoids on the firewall. Am I supposed to replace the top and bottom? Just from memory, I recall each solenoid having two ports, and the vacuum lines look like they go to the bottom ports of each solenoid, there are red and white lines going to the top ports of each solenoid. If I test the vacuum lines/solenoids to see if one is bad, do I just pull on the bottom pink and blue lines, and reverse them and put them back on?

Thanks
Mike

 

I've been through the solinoid/front axel lever issues. The awd and 4x4 light ALWAYS still worked. I'd say your issue is in the transfer case (motor/sensor or box/switch that drives them) Mark 97 EXP 4x4

 

The solinoids may not get the ON signal till transfer case sensors are satisfied, the vacuum action can be tested easy enough. I'd see if the voltage across the solinoids shows that they are being asked to turn on. It should have one or the other on when running (lock or not) I had a bad solinoid (about $25 at dealer) coil measured open (should be about 60 ohms or so). The system does not know the status of vacuum motor, only turns on the one it wants. Soooo if it fails , it does not know to "not " turn on the 4x4 light etc... search for transfer case sensors etc Just my $.02

 

If the light doesn`t light then it isn`t the front axle. engage 4x4 and lift and support the front wheels and try to turn the front drive shaft. If it doesn`t turn then the t-case is not engaging.

JMC

 

Other than buying a shop manual, which is probably what I should do, maybe a shop CD, are there pictures or anything anywhere that would show me where the transfer case/transfer case motor/transfer case sensors are? If I buy a transfer case motor, will that include the sensors, or do I have to buy those also?

Where on the solenoids do I test them to see if they are working?

There are two hoses that come up off of the front differential vacuum motor, one has the (2) vacuum lines inside, and the other is just a small radiator type hose, that stops, by the passenger wheel well. A ford picture that the shop faxed me, shows that there is supposed to be a plug in the end of that hose (Ford P/N 3N271). Is that any significance? What is that for? Is that just something to keep any crap from getting in the tube, or is that what creates the vacuum?

I was told that the transfer case motor is any easy install. 4 bolts and a line. Is that everyone elses impression? Is there a way of telling whether the transfer case, or the transfer case motor is bad?

Sorry, for so many questions, I'm just trying to do whatever I can, to avoid bringing the truck into the dealer.

Thanks again everyone.

 

The third hose is the breather tube for the front differential. it is a lot easier and cheaper to replace a transfer case shift motor than a complete transfer case. if you can tell me if the front drive shaft turns you will be a long way towards finding out what is wrong with the system. If I had to guess at what the problem was I wouldsay either switch or the T-case motor.


JMC

 

So, the plug that is supposed to be in the end of the breather hose, is not a necessity?

Where is the transfer case motor, and the transfer case motor sensor, on the truck?

If I replace parts in the order of the least expensive first, do I replace the sensor first, and if it is not the sensor, move on to the motor? Is this somewhat easy to do, unbolt old one, bolt on new one and hook up lines.

The guy at the garage told me that the axle was going in, so it wouldn't be the transfer case motor. (Whatever that meant), but he is also the same guy that said that they would "start" by replacing the front vacuum motor. I was hoping the guy could have told me what the problem was, not, let's "start" replacing parts, and stop when the 4X4 works. There is six inches of snow out right now, and it is 12 degress, thats why I have jacked up the truck yet.

 

In your last posting, you said, "either switch or transfer case motor".

By, "Switch", do you mean, "Vacuum Solenoid", or "Transfer Case Motor Sensor"

 

I mean the switch on the dash that you turn to engage 4x4. The contact plates in the transfer case are part of the t-case motor. Why do you want to start throwing parts at this problem? Would it not be easier to diagnose the system and only replace the deffective ones? Now, as a concerned fellow F-150 member I say to you: Stay away from the Àsshole that told you; that my 4X4 probably wasn't engaging because I needed a Front Differential Vacuum Motor. You have already replaced it and it still isn't fixed. What makes you sure that his next guess will fix the problem?

JMC

 

IF JMC will allow me to put words in his mouth, by 'switch' he meant 'the switch on the dash'

The light is controlled by the GEM. When you select the shift by twisting the ****, the motor turns the transfer case shaft, engaging the lockup collar. When the motor rotates, there are a set of contacts inside it that send a feedback signal to the GEM that says, "I'm at XXX position." If those contacts send the signal that it's in 4high, the GEM say, "Hey, the motor is in 4x4hi, turn the 4x4 light on the dash on."

Yours isn't getting that far (or at least that's what we're assuming). You need to turn the key on, then flip the switch to 4hi. Leave the switch in 4high. Then, crawl under the truck (with the front wheels on jack stands, of course) and see if the front driveshaft will turn. If the front driveshaft can turn, the transfer case did not engage 4wd.

Now, what causes it? Tough to tell.... If none of the lights are blinking, I would suspect a bum switch. A simple swap with someone that has a good working one can check that.

Generally, if the GEM is receiving the proper inputs from the switch, but the motor does not shift, it'll flash the 4x4 lights. If it DOES complete the shift, the lights should come on.

The easiest way to troubleshoot it is with a NGS test stand at the dealership. They'll plug it in, flip the switch, and see what the GEM is seeing for inputs and outputs. It could be money well-spent for the diagnostic.

-Joe

 

OK here is the thing. If you do not confirm that the front driveshaft either turns or not when in 4x4 you could spend a lot of money on replacing parts that are not needed. With the front wheels in the air they will offer no resistance when you turn the front drive shaft. If you engage 4x4 and you are able to turn the front drive shaft then for some reason the t-case did not shift into 4x4. If it did shift the front driveshaft would be locked and cound not turn becasue the rear wheels are still on the ground. So untill you can complete this test I can go no further in helping. It would be a huge waste of time. Now, to answer your other questions; The breather hose cap is not necessary. The t-case shift motor is at the rear of the t-case. Here is a diagram.


JMC

 

OK, just a few more things.

1) I do not have a switch in the dash. I have a floor shifter for 4WD, if that makes any difference.

2) The "4X4" dash light, lights up on startup but then turns off. So, the electrical part works.

3) Thanks for the motor diagram, it helps when I at least know what I'm looking for, seeing as though, I am totally clueless when it comes to this stuff. Like, what is a GEM? I don't want to seem like I keep asking the same questions but, no one has said yet where the transfer case is.

Send all razzing to me, I can handle it. I know about as much about my truck as if I would let my wife try to figure it out.

 

From your original post:

I was assuming you had the electronic shifter because of these statements.

It can't be the transfer case shift motor because (if you have the floor shift) you don't have a motor.

Once again, shift into 4wd and see if the front driveshaft locks to the transfer case. If it does, we'll look more closely at the front axle. If not, you've clearly got a transfer case issue.

GEM stands for General Electronics Module. Basically it's the brain that controls all the accessory functions, essentially everything electronic except the engine and transmission.

If I was going to guess, I'd guess it was the feedback to the GEM from teh t-case. The GEM isn't finding out that the t-case is engaged and, therefore, isn't locking the front axle. Again, without a diagnostic system to tell us what the GEM is seeing from the t-case, there's no way to know exactly where the problem is.

Start with the front driveshaft check.

-Joe

 

Yeah, wow... If you pull the shifter and all is well, the xfer case IS engaged. Take the ten minutes to do JMCs test. Heck for grins pull it down into low range and see if you max out at 30some MPH.

Adrianspeeder

 

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