http://https://www.f150online.com/fo...then-some.html

I have been through the thread above and posted my problem in it to no avail. I realized it might not get as many views as it is in the technical articles section. I figured I might get more eyes/ideas here.

The truck is a 2006 fx4 crew cab with around 120,000 miles. I started having a problem where the 4x4 would disengage under load and then re-engage after a while when I let off the accelerator. For example: I put the truck in 4x4 high, light comes on stays on the entire time. I start to crawl slowly up a grass covered slope. It starts out fine, then as more load is applied to continue up the slope, I hear a bang/clunk and the rear tires start to slip as fronts are disengaged. I let off the accelerator and the tires re-engage. Repeat.

I read through the above link and started off by replacing the hubs and actuators as the gears on both looked a little worn anyway. The parts were replaced with the appropriate motorcraft parts. This fixed my ABS light but the 4x4 was still acting up.

Next, I replaced both of the check valves with the corresponding motorcraft part numbers. One of the old ones had turned into a two-way "valve" so I had my hopes up, but still the problem persisted.

So I bought a vacuum gauge and tested the vacuum system. Everything held and released vacuum per spec. I bought a new solenoid just to rule that out as well. I already had the updated part but figured what the hell.

I did read on here that the member Josiah was possibly having the same issue a few years ago, but he never really updated on the solution to situation that I could find.

I am thinking about purchasing a used transfer case off ebay for around $200 shipped. I just have a hard time believing the transfer case is broke. The truck hasn't seen heavy offroad duty in about 3 years and the problem just popped up last winter. Before that, it was just Silver Lake sand dune action. Nothing too hardcore, no submerged water crossings or jumping.

Any thoughts or ideas would be greatly appreciated.

 

Are the hubs (IWE) releasing or is the transfer case disengaging? Can you determine which?

 

glc

It is hard to tell. At this point, my ears tell me it is the transfer case disengaging as it sounds more under the truck. I realize this is not very scientific. I will try to have someone in the driver seat driving up the incline and watch/listen from outside the truck.
I realize the cv shaft would still be spinning if the iwe was "released." I am going to have to find another incline to test on as I am not too keen on the rear tires digging more holes in my yard when the front disengages.

One more point to add. I have subbed in a brand new motorcraft cv axle on each side.

 

After further testing over the weekend, it is definitely the transfer case disengaging. I'll be pulling it out this week and taking it to the local transmission shop.

Does anyone know of any upgraded parts for this transfer case?

 

I took the transfer case into the the tranny shop. They split the case and gave me a call. Perfect condition. WTF? I'm lost.

I guess that leaves the engagement motor, the electronic switch on the dash, or the front differential. I'm up for any ideas or past experiences you all have had.

 

well I have a 99 f150 4x4 and my truck seemed to be stuck in 4lo so i took it to ford and they found it was the 4x4 motor. 613 dollars later my truck has a new 4x4 motor and works perfect. I dont know if this helps but it sounds like the motor.

 

This happened to my truck awhile back but I just thought it was a fluke accident. It has only happened once since then but I don't try it out that much. Keep us posted on what you find out. I might run into the same problem in the near future...

 

I ordered a new transfer case engagement motor off RockAuto. It should be delivered the 6th. I will keep the thread updated.

 

I'm stumped. The issue remains with a new transfer case engagement motor. I don't do electronics and I'm 98% sure that's where the problem lies. I guess it's time to take it to the dealer. I will update after I take it in.

 

Good luck.....interested to know what it is.

 

I have one more data point to add. The truck acts just like it should in 4x4, while in REVERSE??? It will climb all over the hill or bury the truck down to the frame. Putting it back in 1,2,D still results in the same disengagement issues. I will conquer this...eventually. Any thoughts or comments are still welcome.

 

Have you checked vacuum on highway or under conditions your experience the problem, or did you just check it at idle?

You have already replaced check valves and hubs so it could be a hole in the line. It sounds to me though its on up the system more. I just messed with my 4 wheel and it memory serves me correct it actually reduces vacuum pressure in 4 wheel drive. So for yours to be falling back into 2 wheel means its gaining pressure. This is not an indicator of a leak to me at this point.

Maybe that amount of information may help you narrow it down with what is left on your system. Just for sh*ts and gigs put a t in your vacuum line and run a long hose up through the window into the cab. See whats happening with the pressure when it disengauges. This will for sure tell you whether its a vacuum problem or not.

 

Watson

I have not checked vacuum under the "loaded" condition. Only at idle.

I have unplugged the vacuum lines at the hubs and tested it for this very reason. There is no way (that I can think of) that the hubs could gain vacuum to put it in 2 wheel drive with no lines attached.

The half-shafts stop spinning when my 4x4 "unexpectedly" disengages. However, I will give your suggestion a try just for the hell of it as I already bought a vacuum gauge during my diagnosis of this issue. Thanks for the input.

 

If you have already pulled the vacuum lines from the hubs and it still stops pulling its not a vacuum at the hub issue.

You have replaced your transfercase and engagment motor. Have you checked the front drive axle? Can you grab the driveshaft and move it with a lot of play?

 

Are you talking about the cv axles or the front drive-shaft? I have swapped a new motorcraft cv shaft side to side. The front driveshaft seems fine. Fine enough to dig all four wheels until the truck was on the frame (this was done in reverse, also in a red mist).

The reverse thing baffles me. Unfortunately, by now, I am pretty familiar with the vacuum and mechanical system on the truck. I only thought about doing the reverse thing after seeing two different relays for CW (clockwise), and CCW (counter-clockwise). Beyond checking fuses and relays and basic plug 'n' play stuff, electrical is not my forte.