How to: - The Borg Warner 4405 Transfer Case Rebuild Diary | Page 7 | Ford Explorer Forums - Serious Explorations

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How to: The Borg Warner 4405 Transfer Case Rebuild Diary

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My 4x4 went out. I have 2 transfer cases and I might just dig into my spare and rebuild it. Thank you for the awesome write up.

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old thread but actual as always. Rebuilding transfer cases like working on a assembly line i stumbled over these notches.
Did anyone have information about the sense of these notches?
Must they lined up? Kind of oilchannel?


I just developed a problem with my 99 XLT. It seems that the TC is stuck in 4wd all the time. The truck binds up bad when trying to make a turn
I disconnected the shift motor, tested, and that is working fine.
I can also put the truck in 4Lo fine.
I disconnected front driveshaft, and now the truck drives fine, no binding.
With the truck off, if I put in neutral and roll truck, I can see the front output of the TC turn, telling me its mechanically locked up inside the TC.
Any thoughts?

Hi Mike,

the transfer case is always turning, if in neutral or drive.
If you shut off the Explorer, shift to neutral, you should
be able to spin the output flange
(with disconnected front driveshaft)
with some effort (caus of the clutch).
If there is no spinning possible, then you have an mechanical blockade
inside the BW4405.

If you could spin, i think there is an electrical problem with
the brown wire which supports the magnetic coil.
Maybe the coil is "under fire" in every condition.
The coil (from 5-12V) should close the clutch only if
the sensors registrate a spinning rear wheel.
Maybe a sensor (rear diff, 2 sensors of the TC) send wrong information?

If you treat your TC fine it last forever, so i don't think it's a mechanical problem.
Nerver heard that the clutch burned together or something.
There are some wear out parts yes, but they don't cause the TC to lock.

Did you ever changed the fluid?
If not, let the oil out and look for metal/aluminium/copper particles.
Take out the 2 sensors and look for broken magnets.

Good luck!


Thanks, I will try the test in neutral when I get home.
After this problem happened, I did change the fluid in an attempt to hopefully fix it, it did look black, but I did not see any metal parts.
The 2 sensors in the TC are pretty much frozen in there even after removing the bolt. I tried to remove them, but they are breaking apart , I just left alone for now.


yes the sensor's struggeling sometimes.
Twist them a litte bit, then push them up carefully (they are expensive)
with two srcewdrivers.

Broken magnet

Black oil isn't good, it should be red like transmission oil.
No metal flakes is a good sign.
Long time ago that the TC do it's job well?

You don't have any dtc's or blinking 4x4 lights?

kind regards


The TC was working fine recently, use it on the beach

Would broken sensors cause the 4wd to always be engaged though?

No blinking lights on dash.

I think they could, they measures continously the rpm's between rear diff
an TC, differences causing the control module to fire up the coil.
If a sensor is bad, the control module analyse this as differences
-> power to the coil -> clutch engages.
You could also measure the brown wire,
it always has 5V in standby, rising up to 12V while engaging the clutch.
With installed front shaft and pulled shift motor plug, you also could test
the front binding.
All tests are better than removing/opening the TC.


I tried the test in neutral still no good.
I can’t turn the front output flange.
I even tried the test with the battery disconnected thinking somehow the clutch was energized while truck was off, but still can’t turn it.
Any ideas?

Any ideas?

No chance to spin the flange with a litte power?
So there must be something locking inside.
You know what that mean, sorry.

Maybe some other's have an idea...

regards Wolfgang

The gear that controls 4x4 is seized and the TC needs to be built. Same thing happened to mine and I had to take it out and rebuild it. Shift motor also needs to be replaced. The nylon bearings (three) inside the shift motor deteriorate over time and freezes up the motor.

I wonder if I’m better off getting a used TC at a junkyard.

The gear that controls 4x4 is seized and the TC needs to be built. Same thing happened to mine and I had to take it out and rebuild it. Shift motor also needs to be replaced. The nylon bearings (three) inside the shift motor deteriorate over time and freezes up the motor.

Would you mind providing the parts or kits you had to get to repair your issue with the seized gear?
I might try to tackle this myself to rebuild it.

The seized gear, may be Rick talking about this one
BW 4405, Range Slider [315645A] - $36.99 | Cobra Transmission

But maybe you need some other parts (clutch/shiftfork/metal spring), who knows without looking inside?
If you like to rebuild the transfer case, you should order a kit like this
BW 4405, Bearing Kit [BK4405] - $53.99 | Cobra Transmission
and the chain
BW 4405, Chain [HV-070] - $124.99 | Cobra Transmission
maybe the spring, it brakes sometime
BW4405, BW4406, BW4411, BW4416 Clutch Pack Spring [U345853] - $9.99 | Cobra Transmission
maybe the range fork
BW 4405, Range Fork [345840K] - $20.99 | Cobra Transmission

cobratransmission provide all other parts for the 4405
shift motor
BW 4405, Shift Motor [A345420] - $140.99 | Cobra Transmission

Good luck!