i have a 1997 supercab 4.6l auto 4x4.
I was on my way home from checking out a college and i was sitting at a red light, waiting to turn left. i took off and i looked down after i went straight and i had no speedometer, then the OD light started flashing. i tried shutting it down to make the light go away and it didnt stop flashing like it use to. there is a set of wires that have made their way toward the left front tire and have rubbed a few times on something, they come up and go to connecters underneath the airbox, and back into the frame where i didnt follow it.

so i need a run down of things to check, right now im gonna go crawl underneath the truck and find out if theres any wiring blatantly broken or something to that effect.

 

from what ive read if the speedometer gear in the drivetrain is bad i would have bad shifting and i dont so where does that lead me to? anyone wanna help? ive had 20 views but no replies, a bit of help would be great.

 

Since you have the mechanical speedo, the most likely cause is the little gear on the end of the speedo cable where it goes into the tranny. It's plastic and may break on occasion. They are only U$10 to U$20 at the dealer and take a few minutes to change. Or, it could be the gear inside the tranny or the cable itself being broke.
The OD flashes because the computer/tranny can't sense the speed anymore.

Fritz

 

well if it was in the tranny wouldnt i experience erratic shifting? what else would allow me to have normal shifting but no speed readout? ford said the VSS could be the culprit but my chiltons book says thats a mechanical gear in the rear diff, would that make sense if that was the one wore out?

 

the VSS in the rear diff has no ohms of resistance read out when i test it, would that signal a bad sensor then?

 

i've had the same thing happen to my diesel...the speedometer does not move and the od lite on the shifter starts blinking..i usually pull over shut it off ..wait 10 seconds restart and everythings fine!..its done it twice in about 8 months but thats the "fix" i use...zap!

 

There is no VSS in the rear differential. That is the ABS sensor plug on the top of the differential housing.
The VSS is at the side of the tranny.

Fritz

 

well thats chiltons/haynes for ya, crappy quality.
ill go check that sensor out tmorrow.

 

Don't know if the 97 is the same, but my 99 Expedition w/ 4R100 dropped off the rear speedo gear and I lost the trans towing home.
The speedo gear is pressed onto the end of the shft and uses a sensor to tell the speed. I was 6 hours from home towing a 6Klbs trailer through Pa. The torque converter sounded like a can of marbles by the time I got home. POS Ford.

 

It is still a vehicle speed sensor, it is just not the one for the speedometer. On your 97 you have a plastic gear on the tranny tail. If the VSS on your rear has no resistance it is bad and you normally should have an abs light on on your dash. I believe it should measure around 1200 ohms give or take.

 

ok current issue, i pulled the speedo gear out and spun her and it read 15mph. stick her back in and nothing again, no speed...

the new sensor for the rear end still doesnt read any ohms.

 

took speedo gear out, spun it and it read 15mph, put it back in and nobody home. ford shipped me a big *** circle plastic gear w/ grooves in it and i dont see how that spins the little speedo gear.

 

what all do i need to do/ how do i replace the inner speedo gear, the round grooved one, not the one w/ teeth that can be pulled out w/ sensor?