[smokum]

My electronic shift 4x4 will not engage in low. When I turn the switch from 2 to 4-hi, I do so in neutral, and everything works fine. I then procede to turn the switch to 4-low, and the light comes on, but nobody is home. No forward or rearward motion, and a terrible grinding if I try to put it in park. If I switch back to 4-hi, the low range light will turn back off, it will "clunk" and I can move again.

Where should I start?

BTW: I was on a hill, with my foot on the brake. I even tried letting it roll to move the gears, but to no avail.

 

[nlemerise]

Not having the ESOF tranfer case, I have never had to work on these units BUT here is what the manual says to look at with your symptoms:

4WD mode switch.
Neutral safety switch.
Brake pedal position (BPP) switch.
GEM.
Transfer case.
Digital transmission range (TR) sensor.
Circuitry

I'd start by checking the relays and maybe get someone to engage the 4hi to 4low switch while you listen at the tranfer case to see if you can hear/feel if the shift motor is operating.

 

[Cool_Canuck]

[ QUOTE ]
No forward or rearward motion, and a terrible grinding if I try to put it in park. If I switch back to 4-hi, the low range light will turn back off, it will "clunk" and I can move again.

[/ QUOTE ]

That is not a good thing. Sounds like you have a problem with your transfer case not engaging low range properly.

 

[smokum]

[ QUOTE ]
[ QUOTE ]
No forward or rearward motion, and a terrible grinding if I try to put it in park. If I switch back to 4-hi, the low range light will turn back off, it will "clunk" and I can move again.

[/ QUOTE ]

That is not a good thing. Sounds like you have a problem with your transfer case not engaging low range properly.

[/ QUOTE ]

The grinding is the park rod trying to engage the park gear while the guts of the trans are free spinning just from internal drag equalizing their speed to that of the torque converter. Power is going into the transfer case, but the planetary is not engaged.

 

[MOUNTAINMAN444]

[ QUOTE ]
My electronic shift 4x4 will not engage in low. When I turn the switch from 2 to 4-hi, I do so in neutral, and everything works fine. I then procede to turn the switch to 4-low, and the light comes on, but nobody is home. No forward or rearward motion, and a terrible grinding if I try to put it in park. If I switch back to 4-hi, the low range light will turn back off, it will "clunk" and I can move again.

Where should I start?

BTW: I was on a hill, with my foot on the brake. I even tried letting it roll to move the gears, but to no avail.

[/ QUOTE ]

I'd start by trying it again befor I even started trouble shooting. Leave the truck in drive or reverse when you shift it into 4wd high. Try to move the truck a little if you can while it's shifting. When in 4wd high, put your foot on the brakes, then put the truck in neutral and shift it into 4wd low. Put the truck back into drive or reverse, take your foot off the brakes and drive away. Try it that way before you go any further.
Joe

 

[dougger222]

The F250 did what your truck is doing a few years ago. Grinding and not engaging. Called a large Ford dealership and was told it was a leak in the vacume lines near the wheels, $425 to fix $25 in parts, 4 hours. Never tried four low after that, then one day my ac/heat controls started to act funny. The vacume leak was causing the cabin controls to only work on the defrost position.

My mechanic tried a new pump with no luck but managed to bypass the vacume lines going to the front and now the cabin controls work normal.

Recall people on forums using a aftermarket stainless steel covered vacume line for the front end leak problem.

 

[Cool_Canuck]

The transfer case is free wheeling when 4low is selected. Has nothing to do with vacuum.