transfer case question?

[topo4u2]

If I move my switch from 2wd to 4low and the transfer case goes in, does that mean that the electric motor should go in to 4auto no problem? I'm trying to see if my shift motor is ok but maybe having trouble with it. When I flip the switch I do not hear the motor actuate except for the vacuum modulator at the front axle. But truck does for sure go into 4low.

 

[dogfriend]

The shift motor should only move when going from Hi range to Lo range or Lo range to Hi range. It shouldn't do anything when going from 2wd to 4wd Auto.

 

[topo4u2]

Sorry to be asking so many questions but these electronic transfer cases are over complicated!
Anyway, if the shift motor does not move when going from 2wd to 4 auto, how does the transfer case shift inside then? I know for sure because I looked tonight that moving the button to auto engages the vacuum modulator to the front axle.
I took it out to the pits tonight and honestly I could not get the front tires to prove traction, although I was on loose gravel. I event tried in 4low. I still feel that there is no drive coming out of the transfer case. I do hear alot of gear noise when I put it in 4 low so that must be working?
please let me know what you think...Mike. Boy I do not want to have to take my truck back to that Ford dealer.

 

[dogfriend]

An easy way to verify that 4wd Auto works is to put all the wheels up in the air, put it in 4wd Auto, put it in Drive and see if they all turn. Just make sure that it is secure, so it can't fall off the stands.

When you shift from 2wd to 4wd, the vacuum disconnect should engage like you verified, then the GEM sends current to the transfer case clutch coil to engage the clutch (the brown wire that goes into the case). This should cause some of the torque to be sent to the front axle. When all the wheels are turning at the same speed, the amount of torque sent to the front is small (~4%) but if the rear wheels are turning faster than the fronts the GEM will send more torque in increments until the wheel speeds match.

These transfer cases are pretty complicated (you should read the patent on it, if you haven't already) but that's what makes it interesting

 

[topo4u2]

Thanks good info DF. Maybe the connection through that brown wire is crap? Maybe the clutches are crap in the transfer case? I will try and get her off the ground as soon as I can. I'm almost sure that there is NO torque going to the front.
I have an appointment with an independent tranny shop tomorrow to see if they can check it before I even consider going back to Ford...this whole ordeal has been and still is a very big P.O.

 

[dogfriend]

One other thing occurred to me about the problem with the lights on the dash flashing: When you drained the fluid, you said it was really dark. If the fluid had a lot of gunk in it, some of the gunk may have coated the (2) driveshaft speed sensors. Someone else on this board was suggesting that the gunk may interfere with the signal from the sensor. You can remove the sensors from the transfer case and wipe them off to clean off any metal particles.

The dirty fluid makes me wonder about the condition of the clutches, but my understanding is that they are pretty robust.