T-case shift motor, BW 13-54

[Brain]

Borg Warner 13-54, electronic shift:

Pulled the shift motor assembly apart today and was wondering what issues other have had.

The position sensing plate (with the large diameter gear in the worm gear drive) has a bushing over a screw on the back of it that acts like a stop. The bushing is deformed on one side and I was wondering if people have had more problems with the actual motor giving up the ghost or if the motor is just overrunning the sensing locations on this plate/gear (because of the deformed bushing) so that the control module (GEM) loses track of it's position.

I'm planning on posting some pics to help the DIY'ers out there that are having problems with the shift motor, as it seems to be pretty common and winter is here and people are finding themselves without 4WD.

Thanks for any input.

 

[Brain]

bumpity bump - any input?

 

[DeRocha]

The shift motor is comprised of 2 parts. A worm driven motor and a geared position sensor. The Position sensor is notorious for getting "lost". This occurs because the plastic stop inside the sensor breaks apart over time and allows the sensor to travel slightly outside its operating range. If this happens the the 4x4 computer module will have no idea what position the T-cases is in and will shut down and do nothing. Other members have found the position sensor is ok, but a high amp draw on the motor prevents it from shifting. The 4x4 module will supply power to the motor for only several secs in order to switch into 4x4. I believe if the sensor doesn't indicate 4x4 after this time the motor is reversed for several secs negating the switch. A high amp draw typically occurs from lack of use, or from the electrical windings beginning to short out.

My shift motor had a bad position sensor, which eventually (from 6+ months of non use) resulted in a high amp draw. I cleaned and repaired the position sensor and shift motor. I verified the sensor was correctly installed by using a multi-meter and testing its wiring harness (I did have to slightly rotate the shift motor cover 1/8" to obtain the correct continuity). After re-installation 4x4 did NOT work. I then read another post about a high amp draw on the shift motor. I removed the shift motor and directly applied power to it (the two wires going into just the motor). I watched the worm gear rotate for 30 secs and then reversed the wires to run the motor backwards for another 30 secs. I repeated this several more times before re-installing the shift motor. I then pushed the 4x4 button in the cab and a slight clunk later I was in 4x4. This was over a year ago and I've had no problems since. I engage 4x4 a minimum of twice each month to keep it in good working order.

 

[Brain]

OK, I had pulled apart my '92's shift motor (since the t-case was out on a bench) to see what "good" internals looked like before I pulled apart the one from my '91 which was inoperable. After I understood how it basically worked, I left it disassembled (for pictures later) and went after the one in the '91 (still in place).

I maked the sensor cover so I could realign it in the same position as it was. After it was open I took a little bit of 600 grit paper and cleaned the "finger-spring" contacts for the sensor. I applied voltage directly to the two pins on the connector that run the motor and spun it in both directions. I rotated the plastic bushing so that the stop would contact a different place (it still looked pretty good) and stuck everything back together. I had applied some voltage while the motor was still in place, so the position was somwhere other than a normal stopping position. When I turned on the key, it indicated that it was in 4X4 mode. I pressed the 4X4 button and ....nothing. CRUD

Then I pulled and checked the fuse in the main distribution box (under the hood) and all was well there. Then I tried the button again and still nothing. Then I loosened the three torx-head bolts that hold the sensor cover in place, rotated it a bit (CCW), and tried the 4X4 button again, and IT WORKED!!! I did it over and over and then reset the cover to the original position (according to the original matchmarks) and it still worked. I figured it would be best to leave it in the original position until I had all of the t-case issues resolved.

Which brings me to where I am now, with 4x4 working (at least according to the indicator light), but low range doesn't light. When I push on the low range button, both the backlights for 4x4 and low range go off for a while and the low range indicator light doesn't come on. The shift motor doesn't turn at all when the low range button is pushed. I'm pretty confused now. The shift motor controls the shift into low range, right?

 

[DeRocha]

The shift motor does all the switching.. 2H - 4H -4L it rotates the T-Case selector shaft by means of the geared position sensor. In order to make the switch into 4L the transmission must be in neutral and the speed sensor must indicate your going under 3mph (this prevents Trany damage if you were to accidentally press it when going faster). If you remove the shift motor you can manualy rotate the selector shaft with pliers. You don't need to worry about how far to turn the shaft as you will feel a definite indent as the shaft drops slightly as it reaches the next position. Several members have gone wheeling with no shift motor..