as the title states everything....1992 f150 2wd auto e4od tranny 108000miles from ohio.....no cel on, going to try to pull codes tomorrow, i think its the vss due to reserch on this site, please ALL help is needed!

 

With the year of your truck, your speedo, should be cable driven. Thus if it was just the VSS your speedo would still work just fine. But, with speedo not working, I bet that your VSS is still good, just that it may be missing the little gear on the end of it. Or the gear is missing some teeth.

Pull codes, if you get a VSS code, unbolt and pull out the VSS and see if the gear is still on the end of it. If it isn't you'll have fun fishing that plastic piece of chit out of the tail shaft

 

1992 was the first year for the electronic speedometer/odometer. The problem is most likely with the VSS in the rear end. There is no cable drive.

 

changed the vss today.....still no change, no odomiter no speedomiter and shifts outta wack....reset computer also.............PLEASE help....this is dd and need to get to work monday ANY suggestions would be of help

 

It could be one of three things.
It could be that you have fuse 8 or 18 bad.
It could be a bad RABS module, unplug it to see if the speedometer works again to test.
It could be a bad PSOM.

Of course it could always be bad wiring from the VSS sensor to the dash wiring.

 

THANK YOU SUBFORD!!!!!!!!!!!!!!!!!! i owe many thanks to you! it was fuse 8 blown....go figure, but im sure i needed new vss anyway.......test drove it, n it drives like a caddy now!!!!!!!!!!!!!!!!!


THANK YOU!!!!

 

I ALSO DISCONECTED RABS.....dunno why, just to see if it made a diffrence, all i know is it drives amazing!!!!

 

update....now its back to shiftin hard sometimes.....

 

What does the speedometer doing when it shifting hard?
Is the RABS module still unplugged when it is shifting hard?
Does it only happen when you turn the radio on or up?
Did you put a 15 amp fuse back in fuse position 8?

 

speedo holds steady, rabs is still unplugged...radio was off during testing...
replaced with a 15 amp fuse.....

thought for sure i had this thing beat!....took the wife for a ride to show her it was fixed....lol wow that backfired, started shiftin hard as before...but atleast gauges work and its semi-drivable...its back to the pre-gauge failure of shiftin weird when it wants to lol.. it drove perfect for my initial run. dunno what happened withinin the 1/2 hr of waiting to show her but it is what it is

 

You need to clear the codes and take it for a ride until it does it and then check the Stored Codes in the Computer (CM codes).

 

I have a similar issue. My speedometer/odometer stopped working after I replaced the heater core last weekend. I had to remove the metal box (about 4x6x1) that was behind the glove box while replacing the heater core. now my speedometer does not work. Was this the RABS box? Unplugging it does not seem to affect the speedometer.

This was on a '92 F250, 5 spd, diesel.

 

Yes it sounds like the RABS box.
Sound like you might have caused an open in the wiring at that point.

 

What is the PSOM and how do I check it?

 

Programmable Speedometer/Odometer Module. It's located on the back of the instrument cluster. It divides down the signal from the VSS in the rear axle to something the speedometer/odometer and PCM can use. It eliminated the VSS in the tailshaft of the transmission/transfercase around 1991.

I suppose if you could find a wiring diagram you could see if the signal is making it to the PSOM then see if the output signal is there.

PSOM on back of the instrument cluster:


VSS-RABS-PSOM wiring diagram: