Hi all, I have a few questions for the experts out there. Let me start from the beginning- 95 F250 XLT 4x4 with a 460 and E40D trans. A while back while driving home down the freeway, the speedo started going beserk, then quit about 10 miles later. The problem resurfaced on the next trip and never went away. I was headed up to the in-laws to get our 28 foot camp trailer some 12 hours away. A lot of things were going on and it had me concerned- speedo jumping, hard shifts, dying at intersections. I went to the local Ford dealer and asked them, they recommended replacing the VSS in the rear end. Tried that, no luck. So, I hooked onto the trailer and drug it home. Once I got here, I took the truck to the local Ford dealer down here to have them look at it. They checked the exciter ring in the rear end- it's fine also. They also tried a new VSS and that didn't solve the problem. The tech there figured it was the PSOM and explained the electronics to me in a simplified manner. They wanted to charge me 3+ hours of labor plus parts just to see if it was in fact the PSOM, and I couldn't stomach that. I had them button it up and I drove it home so I could tear it apart myself.
Now here I am today- got the gauge cluster out and got the gauges removed (took me all of 45 minutes, taking my time). My question is, can I swap in a PSOM from another truck to see if mine is faulty, or will I need a PSOM from a truck with my same engine and trans configuration? I know that somewhere in the 95-96 model year Ford changed some stuff around so I was just curious. If anyone has any advice or tips on where I can dig around for another PSOM I'd greatly appreciate the help.

 

Any PSOM will work just fine. The clusters themselves are slightly different bewteen certain years, but as far as I know all PSOMs are the same.

 

First off the PSOM will not cause the engine dying at intersections.
All PSOMs I think will sub for testing, there were some problems in the early 90s but they have improved the PSOM from about 1994 on.
The PSOM is where the odometer mileage is stored so you will have whatever mileage on your odometer as the truck you took it out of.
It also is set for your tire size and can be changed about four times to correct the speedometer and shift points.

I would say yes you can put one in from a salvage yard for a test but only Ford can put one in legally.

Sounds more like bad wiring to me.

 

Thanks for the quick replies. subford I have a couple more to throw your way- stock the truck came with 235/85/16's, it now has 265/75/16's. I don't know if the PSOM has ever been reprogrammed for the different tires, but since the height is nearly identical would it make much of a difference? The tech that worked on my truck also suspected a wiring problem between the VSS and the PSOM in the twisted pair- is the twisted pair an easy set to find and trace, or do they get buried in a tangled mess in a harness somewhere along the way?

 

A bad PSOM can cause it to die at intersections; I had it happen with my truck! Here's what happened in my case: At around 1 mph, it would send a signal to the PCM probably saying I was going over 100 mph. So if I coasted to a stop with the clutch in, it would usually die. Getting going was also quite fun. People thought I didn't know how to drive a manual transmission. My engine would also cut out on the highway every time the needle swung down to the high peg.

There were a couple other guys here a few years ago that had similar symptoms with a bad PSOM.

Superduty4x4, if your tires are the same height your speedometer won't be affected. I was wondering about those very sizes as my 97 F-250 has 265/75/16's on it now and the PSOM has never been reprogrammed.

 

Thanks for the info brown 4x4, I'll see if I can round up a used PSOM to see if the problem goes away. If you don't mind me asking, what did the new PSOM set you back?

 

I bought a base model cluster on ebay for around $10. I kept track of the mileage difference and in the meantime found another PSOM with known miles for I think $40. I switched over to it at exactly the right mileage, so now I have the correct mileage.

 

Thanks for the info brown 4x4!

 

Wow! Smart thinking!!

 

I can see how that would happen, I just never heard of one going bad that way.
They usually just work or not from what I have read on this site. Thanks for the information.

 

Well I borrowed a used gauge cluster from the mechanic at the dealer... PSOM is the culprit. Took a short test drive and the speedo tracked true, no weird running, smooth shifts every time. Now to find a 95 tach gauge cluster and swap it out!

 

It does not have to be a tach cluster. Just remove the PSOM from the salvage yard cluster and put it in yours. Try to get one from 1994-1996 if you can but I think ones all the way back to 1992 will work.
Note that a PSOM is where the total mileage and tire size of the truck is keep. You will get the mileage of the truck you remove it from and you will have to reset your tire size in it, this can be done up to four times for the life of the PSOM.
This is not legal but it is what most of the posters do.

The PSOM.

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Yeah I'm aware of all that, but I figured since it's already apart and my PSOM is TU, I may as well try to find another dash cluster with a good PSOM and a tach and do the swap (original cluster does not have a tach). The dealer is checking for me to see if a used PSOM can be re-programmed to show the correct mileage, otherwise I guess I'll have to bend over and buy the part from Ford.

 

Actually, it is not illegal to repair a broken speedo/odo with a used unit. It IS, however, illegal to misrepresent the actual mileage on the vehicle if you try to sell it or trade it. You MUST disclose the fact the odo's been changed and for what purpose, AND disclose the mileage the original had on it when changed, as well as the mileage on the used unit when installed. Just record the numbers from both before you change it, sign it, have it notarized, and stick it in the glove box. I had no intention of selling my old duck. I just wanted a working speedo. If it were illegal to change them, there would be no such thing as aftermarket systems available. It's just illegal to lie about the mileage.

I checked into this when a stealership fried the original digital cluster in my '86 Bird, along with the original stereo, original alternator. Funny, but the ECM even looks like it's been replaced. But they still stuck me for an alternator, which was working just fine when I took the car in for a long-block installation. (I drove it in with ZZ Top blasting on the radio and the headlights on and wipers running, albeit with very weak oil pressure.)

 

after ten years miles is not needed for any legal reasons . and no a used cluster cannot be serviced to the right miles they require a reman and cahrge around 450 if i remember correctly, i swapped out my cluster for a tach cluster it was plug n play but i swapped out my psom for the truck