Hi guys

I just replaced the transfer case BW 4405 And i noticed that the 2 sensores (front drive shaft and rear drive shaft) are bad. Anybody knows what the name of these two sensores? And where I can buy them from? I'm looking for a brand new ones if someone can send me the link where i can buy them i will be very appreciated

Thanks

 

I'm not sure what model year your Explorer is, but there's a really good chance they are just called the "Front speed sensor" and "Rear speed sensor." At least that's what they're called for the 2002 Explorer in the factory service manual.

-Rod

 

Mine is 98 explorer xlt. I saw some people call it hall effect sensors. But i am not able to find it online. Do you know where i can buy one?
Thanks

 

Per the factory service manual, in 1998 they are also called "Front Speed Sensor" and "Rear Speed Sensor." They are Hall Effect sensors, but that's just the method in which they operate, not the function/name of the sensor. ABS wheel speed sensors are also Hall Effect sensors, as are several other types of sensors used to detect rotational motion.

I've never tried to source these sensors so I'm not sure where you can purchase them. I would expect you could order them from a Ford dealership but you'll want to have the FoMoCo part number off of them.

How did you determine the sensors are bad? Have you considered pulling replacements from a salvage yard?

-Rod

 

I replaced the transfer case with a used tested one that came with these 2 sensores and when i took the car for test drive the car stuck in 4 wd it was heavy and made clunk noise. Also 4wd hi and 4wd lo was blinking in the dash So i replaced the shift motor with a brand new one because i thought the old shift motor was stuck on 4wd hi or low. But that did not fix the issue. Then i removed the shift motor and rotate the little cam in transfer case to The end of H position and that did not fix the issue also. Eventually. I unpluged the harness of transfer case and test it. The car is drives fine. This made me think that there is somthing tells the transfer case to engage the 4 wd all the time for me and it might be the sensores or somthing wrong with front drive shaft or front axle. I don't want to get sensores from junk yard coz they might be bad too.

 

I don't recall reading on this forum of common issues with the sensors, and really there's not a whole that that should fail with a Hall Effect sensor which is why I ask.

The means of determining initial wheel slip and telling the transfer case whether or not to engage 4WD would not be via the front speed sensor, but I'll need to review the manual to understand with greater detail the sequence of events.

Are you absolutely certain you got the correct transfer case for your truck? I wonder if maybe you got one for ControlTrac and you need just the manual shift version or something like that. Do you have access to a professional grade scan tool that can access the electronic shift control module for diagnostic information?

-Rod

 

Yes i am sure i got the right transfer case since it has the same ID.
unfortunatly I don't have any pro diagnostic devices. Do they leas them ? I can't afford take my explorer to the mechanic now

 

Here's what the factory service manual says:

Transfer Case Functions
There are three modes on the transfer case, Auto, 4WD Low, and 4WD High. Neutral is only available as a dealer installed option.
C-Trac Function
The C-Trac transfer case transmits torque to the front wheels through an electromechanical clutch assembly. In the Auto mode, while at rest and under cruising conditions, the Generic Electronic Module (GEM) activates the transfer case clutch at a minimum level. This allows for the slight difference between the front and rear driveshafts which occurs normally when negotiating a corner on dry pavement. Under any of the following conditions, the GEM will increase the torque sent through the clutch to the front wheels in order to prevent or control slip.

• Slip is detected (by monitoring the Hall Effect Sensors in the transfer case)
• Heavy acceleration (by using the throttle position signal from the EEC)
• Very light or zero throttle at speeds above 64 km/h (40 mph) (using the throttle position signal from the EEC)

So per this description, you're correct. If the sensors are bad, that could cause the GEM to engage 4WD if it thinks wheels are slipping. It sure would be nice to connect a pro-grade scan tool to monitor those speed sensors first though to make sure they are providing goofy readings.


-Rod

 

Lacking any kind of scan tool, some simple checks can be run with just a DMM or even a visual inspection. It'll just take you some time.

Take your DMM and check for continuity between the pins. An open circuit would be bad. Also, check continuity from each pin to the case/body of the sensor. If there's continuity, that's usually a bad sign for a sensor with two wires (a sensor with one wire is typically grounded through the sensor case, like the old engine temp sensors for your temperature gauge). Remove the sensors and see if there are any metal particles stuck to them. If so, clean and reinstall.

Separate the connectors and visually inspect the pins/sockets on the connectors. I've seen some pins that have turned to green dust.

Also, since some transfer case motors require you to remove pins from the connector to change the motor, there could be the possibility that the donor either had a different pinout or the motor was changed and it was done incorrectly. Do you have the wiring diagram? Check the pinout. If I remember correctly, at least one of the speed sensor wires pass through the transfer case motor connector. The connector that I'm referring to is the 16 pin square connector (only 14 pins are populated).

 

I put a brand new shift motor so i am sure the wires for the shift motor is in correct locations since the new shift motor comes with a harness already.
Do u have diagram for the sensores wires in harness? That will be helpful and i will check them with dmm as you said
Thanks

 

I have the wiring diagram at home for the transfer case and can get that to you this evening.

-Rod

 

Thanks alot shorod. This will be very helpfull

 

Here's the schematic showing the speed sensors in the transfer case:


And here's the C201 connector pinout:


-Rod

 

Thanks alot Shorod!