My dad just got a 95 f150 w/302 e4od. The speedo jumps around at about 50mph. I am thinking it is the vss but not sure. The milage read out sometimes flashes "error 3". Also the Front brakes will lock up on a hard stop in the snow but the rears don't. Is this truck rear abs only? Any help would be great.

 

Yeah sounds like a VSS problem. These trucks have rear abs only not that it or the rear brakes work terribly great anyway, so front wheel lockup on slipery surfaces is normal.

 

I'll second that

 

I'll third that.

 

May not be a VSS problem, if the ABS lamp is not on then the VSS is more than likely OK.
When ERROR 3 message alternate with normal odometer display then you need to RESET conversion constant.

The sensor may be OK but if the RESET of the conversion constant does not take care of the problem then you may need to wipe the VSS off and change oil.
Here are some other things that can cause it.
Damaged, missing or bent teeth
Metal chips on speed sensor
Open or shorted sensor
Improper gap between sensor and speed sensor ring

To RESET conversion constant:

Note: The module can only be reprogrammed six (6) times.

Reprogram speed conversion constant using the following procedure:

Locate the dealer mode programming enable single-terminal connector. The connector is located at the bottom of the instrument panel below the center of the glove box. On all vehicles, the dealer mode enable wire is Circuit 567 (LB/Y).

Insert metal clip in service wire panel connector. Clip other end to vehicle ground while the key is in the OFF position.

Key to RUN while holding down the trip odometer RESET button on speedometer. Release RESET button.

Speedometer will prove out (sweep across dial and back). The English/Metric and revision levels will be displayed. The last number of the display is the dealer mode programming lockout count. This count shows the number of allowable conversion constant changes remaining. When the count is zero (0), no additional changes can be made to this instrument cluster. If a conversion constant change is required, then the PSOM must be replaced.

Press and release RESET button again and PSOM conversion constant (without the decimal point) followed by the word CAL will be displayed.

Press and release the odometer SELECT button as many times as necessary to change conversion constant to the correct value.

Note: Pressing and releasing the RESET button to lock in the new conversion constant reduces the number of times the PSOM can be reprogrammed by one count. The module can only be reprogrammed six times. If you change your mind and want to go back to the old conversion constant, turn the key off before you lock in the new constant.

When the correct new value is displayed in odometer window, press and release the RESET button to lock in the new conversion constant.

Key off. Remove the ground wire. Verify proper speedometer operation.






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thanks guys I will get this info to him asap.

 

Also, I had my speedo jump around the place shortly before the rear end granaded.

 

He says that it isn't noisey so I hope this fixes it. A dealership told him that the error3 message means to replace the whole instrument cluster.

 

Not true, read my post above, my reply is what the Ford shop manual says.
At most you would have to replace the PSOM.

 

Thanks, I was hopeing you would say that. I did read that post but want ot check on the other info as well. I will let him know that it is not the cluster for sure.