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Eric
Eric, Automotive Repair Shop Manager
Category: Ford
Satisfied Customers: 30812
Experience:  Automotive Repair Shop Manager, Technician
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I have a 1999 Ford F250 Super Duty, V10, automatic transmission.

Resolved Question:

I have a 1999 Ford F250 Super Duty, V10, automatic transmission. Problem: while driving today the service engine light and the ABS light suddenly came on. Further my transmission began shifting very hard and the speedometer stopped working. This happened shortly after first startup today. No previous symptoms. Ran great yesterday. Can you Help??
Submitted: 7 years ago.
Category: Ford
Expert:  Eric replied 7 years ago.

Hi,

 

This is most likely a faulty VSS(vehicle speed sensor), or related to it, as it will set both the Check engine light and ABS light, and will cause speedometer problem and erratic shifting

 

I do strongly suggest having the on-board computer read for fault codes before replacing any parts. Most major auto parts stores, such as Autozone, will do this for free.

 

If the code is for the VSS, below is how to test VSS to confirm it is bad and not a wiring harness problem:

 

TESTING

 

  1. Disconnect the negative battery cable.
  2. Disengage the wiring harness connector from the VSS.
  3. Using a Digital Volt-Ohmmeter (DVOM), measure the resistance (ohmmeter function) between the sensor terminals. If the resistance is 190-250 ohms, the sensor is okay.

 

It is located in the left rear of the transmission at the tailshaft housing:

 

Click image to see an enlarged view

Fig. Fig. 2 Detach the connector for the VSS sensor



Click image to see an enlarged view

Fig. Fig. 3 Remove the retaining bolt for the VSS sensor and ...



Click image to see an enlarged view

Fig. Fig. 4 ... remove the VSS sensor from the transmission



Click image to see an enlarged view

Fig. Fig. 5 Pry the retainer for the VSS gear off and ...



Click image to see an enlarged view

Fig. Fig. 6 ... remove the gear from the VSS

  1. Disconnect the negative battery cable.
  2. Raise and safely support the vehicle securely on jackstands.
  3. Detach the connector for the VSS.
  4. Remove the VSS retaining bolt and remove the VSS from the transmission.
  5. Remove the driven gear retainer and the drive gear.

 

To install:

  1. Inspect the O-ring on the sensor and replace if necessary.
  2. Install the driven gear and the retainer.
  3. Place the VSS into the transmission.
  4. Tighten the retaining bolt to 98-115 inch lbs. (11-13 Nm).
  5. Attach the VSS electrical connector.
  6. Lower the vehicle.
  7. Connect the negative battery cable
Eric and other Ford Specialists are ready to help you
Customer: replied 7 years ago.
Stopped by AUTOZONE as suggested and had the on board computer read. This validated that the Vehicle Speed Sensor was faulty. Great Diagnosis by Eric. I have ordered the part (expected in tomorrow). Thanks for your help. I have used Just Answer only twice but both times the mechanic was right on with the diagnosis. Once was a Honda and this time was a Ford. Thanks guys for a job well done and such a quick response. Nine minutes and 43 second, IMPRESSIVE!