Did you replace the speed sendor in the read end? This is a common sympton of a bad speed sensor.

PSOM is behind the speed and can cause issues too but it's most likely the speed sensor.

 

I changed the speed sensor (That's the same as the ABS sensor, same thing, correct?), but what is the PSOM? I drained the rear end housing and took off the plate off. There were no cracks in the ring teeth that the sensor reads off.

 

Does anyone know here how to check the distance between the tone ring and the VSS? What is the distance supposed to be? 1997 F-250 HD

 

"PSOM" stands for Programmable Speedometer Odometer Module -- on the back of the speed readout in the instrument cluster
most likely this is your problem - broken solder joint on the psom board

Looking for 5-8 thou on tip clearance for all this type of sensor -- the below procedure is a PIA todo -- an actual depth fixture and micrometer would work better

The distance for the VSS is not adjustable, except with shims/grinding -- you can rotate the diff until a tooth is visible thru the VSS hole , then use a small ball of clay on the tip of the VSS , press the VSS(without oring) into the hole until it bottoms -- remove and use a razor blade to slice the clay at the impression -- measure the thickness of the clay

 

Thank you very much. Now I have another question. I be checking the internet for other possible problems. For the first time I seen a response from a auto mechanic that someone gave a question to their speedometer jumping problems. The mechanic responded back that it could be the EMO(?) The module is behind the fuse box. Ford in 1997-1999 models changed how the VSS sent the signal to the cluster. Has anyone found that this was the problem in there case?
I am going after the VSS clearance first and than going to go after the EMO. I have a junk 1995 or 96 pickup, Would these two models interchange with my 1997? I check on Geek and Rock Auto, but neither one sells it
Any more help?

 

Never heard of an EMO , you sure he wasn't talking about the GEM? -- that module has been called various names and been located in a few places by Ford

 

In all my years on this forum I have never heard of the EMO on an OBS. The VSS (speed sensor) is the issue MOST of the time with the exception of a bad connection in the cluster and/or poor ground in the cluster.

The VSS wiring should be checked all the way back to the rear end. I have seen cracked wires and bad splice jobs that lead to these issues as well.

 

I so sorry, I should have checked that link before I opened my mouth. It is indeed called a EMO. Yes, I must have have looked at a 100 post as this is the first and only time this was mentioned. It mounts right behind the interior fuse box. There is a video on you tube of someone taking it out of their 1997 truck only to find out it was their fuse block that was corroded? It said in the post that ford changed the way the VSS sent the signal to the speedometer in the 1997-1999 models and than in 2000 omitted the VSS. I was just so surprised that this possible solution was not bought up more often (If it is a solution).

 

Sorry again, its called the GEM!!!

 

Here is the video on You Tube:

 

Water leaking in around the wiper arm or a rust hole in the windshield cowl trough will drip down on the fuse box causing all kinds of electrical problems
The VSS mounted on the diff housing has been there a long time on these trucks and is where the speedo and ABS(+ front hubs) get the speed signal from
pretty sure the speed signal has always went to the ABS module before heading to the speedo -- check the harness at the ABS module for damage

Reference this thread

02 F250 7.3/6spd No speedo/odo not tracking mileage

Speedo is stuck at zero, odometer isn't tracking movement, only displays last known mileage. No other faulty indications, codes, or red flags. This signal comes from the sensor on the rear diff correct? Any way to test the sensor? I can shoot the wiring I suppose if I can pull a schematic. I'd...

www.powerstroke.org

 

Ignore any F150, gas models etc. The 7.3 OBS is it's own beast and Ford did some odd stuff which is why electrical gremlins are so common on these trucks.

 

Yes, but on the forum, the mechanic was discussing the F-250 HD like my. In reading about the leak at the wiper, I wonder now as I have said before when I was driving in wet weather (Wipers on?) the speedometer would act up. Now I wonder if this was what was going on, since once I got on drier weather conditions this would stop, but now corrosion has set in.

 

If this is the case would their be a seal that is rotten if there is no rust hole by the wiper?

 

97 was a change over year to the bastard F250 7-lug step child.

I'll let Hydro take over. Good luck.

 

97 was a change over year to the bastard F250 7-lug step child.

I'll let Hydro take over. Good luck.

Hang around my friend, you have good information ...this forum is a place for teamwork

 

Thanks, for your information. One question though White95f250, why was it call the 7-lug step child?
Now onto you Hydro, any more information you can give me on this GEM? If this is the problem, just pour water around the wipers to see where it was leaking once the fuse box is out? Would the 95/96 fuse block interchange?
Thanks again fellows

 

If you've ever seen one and talked to someone who owned one you will know. F150 body on an F250 frame with 7 lug nut wheels is just a glimpse.

Once I have access to my computer I can give more information on your current situation.

 

Alright I do not see a GEM on the back of my Fuse Block, is if that is true that that is for a gas model. Does the wires from the VSS run from the sensor with a straight shoot to the firewall and pass though there upward to the speedometer? If the speedometer is acting this way it has nothing to do with the transmission, since the signal comes from the speedometer to the trans?

 

The ABS(RABS) is located behind the glove box, the VSS signal goes there first - then to the PSOM in the instrument cluster -- the GEM should not have anything todo with this, it may be separate from the fuse block on your year but will be still just behind the fuse block

 

See the attachments. Cheers!

 

ABS light is on -- should pull the codes
Cruise still works -- that means the VSS is outputting a signal to the PSOM output, but since the speedo is not working -- the fault is in the speedometer, unless it has a different output for the speedo
Does that make sense?

 

The wires come though the firewall by the diver side than onto behind the glove box to the ABS than onto the PSOM, correct. Could the wire going to the VSS or back to the ABS or the PSOM be shorting out when the trucking is running, even though putting on a contunity testers shows no breakage when the battery cables are unhooked?. Could the ABS be bad, and if so is there a way to check it out.
Thanks so much

 

Well, could not find no broken wires, so I shipped the speedometer out to have it look at. I will keep everyone informed on the site when I get the part back. Thanks to everyone. The truck has over 400,000 miles on it, but I plan on keeping it till it long longer feasible. With two engines and transmissions that i pick up over time it's going to be a long time.
Yes Hydro, I understand how you explained it. That's why I decided on shipping it out.
Thanks to everyone

 

Wanted to give everyone an updated on my truck that might be interested.
I sent the speedometer almost 30 days ago.It was received by the company in 2 days, they fix what ever problems they found in 24 hrs, and shipped it back by USPS ( The same service I used to ship it to them). It took 24 days to get back to me at that point, unbelievable how this COVID 19 is affecting mail service.
Anyways, put the speedometer back in, it did not seem to help anything, put the the original computer back in ( Which I had changed from a different truck) and it seemed to work, but after a few miles it started to do the same. I was just about to send the computer in to have it check out, but really didn't want to since the mail service was so bad. I went and sprayed the male and female pins of the computer with electrical cleaner and it seems now that my problem is solved.
The tech at the company where I sent it to said that the speedometer was not working correctly, so if that was the original problem or I had a bad connection from dirt or rust in the computer pins, or a combination of both I don't know . I am just glad to have my truck back on the road.
Again, thanks to everyone that gave advice on this subject, hope that this information might help someone down the road. One of the most important lesson I learned was to have my items sent by Priority Mail. Never again will I make this mistake. The post office told me you couldn't start a case for lost mail till 30 days had past .

 

Glad it working! Thanks for the update. Cheers!