Well if the light is coming on then your transfer case motor is working. But maybe not working enough. The motor might be trying to switch to 4WD, and turns just enough to trigger the light but not engage 4WD. Get under the truck and on the transfer case is a motor on the side of the case that looks like a windshield wiper motor. Give it a couple wacks with a rubber mallet (but not too hard) and see if that frees it up enough to let it engage. If it does than your trasfer case switch motor was just frozen up a bit, which is common on these trucks.
If that doesnt cure it, you could probably for testing purposes get a new switch motor and throw it on, but keep it clean and nice cause if that doesnt fix the problem you can take it back and telll them you didnt need it. Just use it as a test to make sure that isnt the problem.
If you still have the problem you might want to look at the IWE vacuum solenoid under the cowl behind the battery, this peice might be shot and not allowing the vacuum to escape the system to engage the wheel ends to put the truck in 4WD. A way you can check if that is the problem is crawl under the front of the truck. Coming down behind the spindle of each wheel is a double vacuum hose, pull that off both sides, then just to test put your truck in 4WD and see if it is engaged (obviously not while its is jacked up and you under it). If it is engaged at that point then i would start by getting a new IWE solenoid. Because what your doing by pulling off those lines is letting the vacuum escape from the IWE system. The vacuum holds the wheel ends at a disengaged state. When the vacuum is lost it locks the wheels in. If that still doesnt fix your problem you might have siezed up IWE actuators (wheel ends) which wont engage or disengage with vacuum no matter what. At this point jack the front of the truck up just so the tires clear the ground. Turn the truck on and in 2WD, crawl under the front. (With the vacuum hoses on) spin the tires, the tires should spin without turning the halfshafts. Now unplug the vacuum hoses again behind the wheels. Now spin the tires, if everything is working fine with the wheel ends then by pulling the hoses off it should have locked in the wheel ends and now when the tires spin the half shaft should spin with them. If the tires still spin free, i think you will probably need new IWE actuators (wheel ends)
So when you switch into 4WD, two things happen. The transfer case switch motor engages the tranfer case and puts power to the front end. Then the IWE solenoid releases vacuum from the 4WD system which engages the front wheels to the half shafts.
Thank you both. I'll take a look at it this weekend, working from the simplest and cheapest solution first. Will try to post back the results when I finally figure it out, hopefully soon. Thanks a lot.
Well, I finally got to checking out my 4WD... after a snow storm or two and maple sugaring done. My truck is a F150 XLT with 5.4 liter motor with both the trailer package and the plow package and automatic transmission.
1- I looked for the small motor you spoke of but did not see one you mentioned.... however because my transfer case has the stick to engage 4WD I figured maybe there shouldn't be one but the lever should flip a switch to trigger the vacuum switch on the firewall. Am I anywhere near correct?
2- Next I made the mistake of replacing the IWE vacuum switch on the firewall ($28). Still no 4WD.
3- So I went back to your recommendations. Raised both front wheels. With the motor off I spun the left wheel and its half shaft turned. I spun the right wheel and its half shaft did not turn.
I assume based on #3 that I would need a new IWE wheel actuator. Is that a safe assumption? If so, should I replace both or just the one that is not working?
Last edited by srgntrbt; 04-20-2011 at 09:01 PM.
Reason: added automatic transmission.
The half shafts should turn when the motor is off, so the right OWE might be froze to where is isn't engaging. That would be the one I would replace. But you should get a vacuum gauge and check everything per my write up in the Everything you need to know about the IWE system and then some, thread.
Sorry, my last post i was writing on the go from my phone, i meant froze to where it isnt disengaging (or the teeth on the gears that mesh are wore off from grinding). And if that is the case and its all corroded or wore out there could be a vacuum leak in that bad actuator, which in turn would allow the vacuum to leak in the entire system which would then, while under load, would let the other side try to engage and grind. But the absolute best way to go about this is to get a vacuum guage, about $60 from any parts store and start testing parts and lines. This is alot cheaper than just starting to throw parts at it. Plus is lets you understand how the system works better. And if you take it to the dealer or a shop, make sure you explain it all to them cause from what i read on hear, alot of repair places, even dealerships, have a hard time with this (even though its so simple)
The acutators are not hard to replace, if you have done ball joints and wheel bearings before, its basically the same tear down procedure.
Thanks again, I'll work on it hopefully within the week. Its been a few years since I've done ball joints or wheel bearings but now that I'm retired I have the time and not the money I have incentive once again.:-) as long as I don't get too lazy.
I did forget to mention in my last post that I had been able to shift it into LOW Range 4WD and drove it a short distance on my gravel road. It acted as it should, very slow and I could hear the additional "whine" so with that info I had assumed the transfer case was engaging correctly. I have to admit it is not easy to shift into low range but it can be done.
Well, if self diagnosing, and trying to save money, try to do one thing at a time. That IWE obviously needs replaced. Once replaced you might find that your other problems might go away. And in my opinion, if you do replace one, if you have the $ and time, do them both, because if one goes, the other probably isnt far behind.