star69

READY TO BURN IT. i replaced the IWE solenoid. I removed, disassembled , inspected , reassembled and reinstalled the transfercase. I vacuum tested and than removed, Inspected and reinstalled both front iwe ,axles, and hubs .
Still only has 4 wheel ONLY in reverse. It seems to have 4 in forward unless it is under a load where it needs front traction, than it seems to pop out. That it why i removed and inspected to see if the were any rounded teeth on the iwe hubs and transfercase.
Any more suggestions would be appreciated - I THINK

EBC-150

Are your vacuum 'bleed-off' tubes clear of debris? These are the small tubes to the IWE's that terminate up at the frame rail by the UCA's. I had an issue with one wheel popping out after mudding and slush. Turns out the upper end (open to the elements) was plugged and not allowing the vacuum to bleed off- keeping the wheel partially disengaged. I disconnected the lines from the IWE and blew air through the small line and all was better.

homer

Like EBC-150 mentioned, if you pull the vacuum line and just leave it off, does it still pop out? Also, does it pop back in after the load is off, or do you have to shift out of 4x4 then back in?

dean6510

on mine i replaced both front air lines. still have problem. if i look underneath while friend accelerates up a slope i can see the front driveshaft spin then pop pop and it dissinggages no more spin that why i dont think the iwe have any thing to do with my problem as the drive shaft does not spin anymore. has to be the transfer case .

jt351

had one act similar to this ended up being a hub. I too thought it couldn't be cause vacuum disconnects, found out the spring inside rubber boot of hub had rusted to pieces so it never fully engaged and sometime made clicking sounds. with vehicle off and and in 2wd there should be no vacuum and hubs should be locked in, use a large screw driver or prybar and stick in driversaft and turn, it shouldn't, if it does you will find problem.

VTX1800N1

As suggested, eliminate the vacuum system and see if it still has the problem. You can do this by disconnecting the vacuum hoses at the IWE (but don't drive like this for long because water and dirt will get sucked into the system) or disconnect the vacuum at the solenoid.

If the problem goes away, the issue is vacuum based. Either the solenoid is passing vacuum when it shouldn't (yes you can get a bad one brand new) or the control system is energizing the solenoid when it should not. It's possible a chafed or loose electrical wire is moved in just the wrong way when in drive vs reverse and that is why you are experiencing this issue.

Much more likely is that the problem will continue after vacuum is eliminated. This would mean a problem with the hubs or IWEs (most likely) or the transfer case (rare).

My bet is the hub/IWE interface. The vast majority of 4WD operation will be in drive. That means only one side of the hub gear teeth and the opposite side of the IWE teeth are subject to engine torque. This causes wear on that side of the teeth, but the side that sees torque in reverse would be virtually factory new. My guess is one or both IWEs is not fully engaging. The collar spring might be broken or rusted. If it's partially engaged, with worn teeth in the forward direction, you might get slippage, hence the grinding sound. In reverse, with the still new teeth surfaces, there might be enough holding power that no slippage occurs. By eliminating the vacuum system, you can narrow your search for the problem significantly. If just one hub/IWE slips, you will lose all pull from the front.

VTX1800N1

Also see: https://www.f150forum.com/f72/how-di...72/?styleid=14

jt351

Well if its not the transfer case motor sounds like a shift fork is bent or sometime of internal damage to transfer case then.

star69

i think i am making progress. There is no signal to the TC clutch.If i send a 12v source to the Transfercase clutch magnet it will will properly. Does anyone knows what signals it. I know it gets the signal from the PCM which has a relay in it for clutch. I need to know if something like the shift motor signals the PCM to engage the relay in turn energizing the magnet. There is no TC speed sensor on this vehicle . I can not locate a schematic that shows this system.

jt351

Accordinge to my ondemand mitchell the ecm directly grounds the clutch, no relay. only relays control the motor itself, here is the description of operation out of mitchell.
The transfer case is equipped with an electromagnetic clutch which is located inside the case. This clutch is used to synchronize the front driveline. When the mode select switch (MSS) on the instrument panel is turned, the 4x4 module (PCM) activates the electromagnetic clutch and powers the transfer case shift motor. When the shift motor reaches the desired position, as determined by the contact plate position inputs to the 4x4 module (PCM), power to the shift motor will be removed. When the transfer case front and rear output shafts are synchronized, the spring-loaded lockup collar mechanically engages the mainshaft hub to the drive sprocket. Finally, the front axle integrated wheel ends (IWEs) are engaged and the electromagnetic clutch is deactivated.
hope this helps