not upshifting

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May 20, 2020 | 11:17 AM

akpolaris

Thread Starter

Junior User

Joined: Aug 2010

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not upshifting

Intermittent problem at the moment but ….. When initially starting the truck remains in 1st gear, not upshifting as acceleration occurs. The speedo will not work during this time. I haven't quite figured out the sequence much better than this. I stop and go to park, back to drive and a reverse to mix things up. It is a 97 F350, 7.3 ltr, automatic trans. Any ideas where to start

Thanks

May 20, 2020 | 01:37 PM

Mark Kovalsky

Frmr Ford Trans Engr

Joined: Aug 1999

Posts: 24,732

Likes: 2,661

From: SE Florida

That can be the VSS (vehicle speed sensor) in the rear axle, or the PSOM (Programmable Speedo/Odomemter Module) located on the back side of the instrument cluster. Or it is an intermittent problem with the wiring between those two.

May 20, 2020 | 09:00 PM

akpolaris

Thread Starter

Junior User

Joined: Aug 2010

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thanks, something to look at I guess. Is there a way to test these sensors other than replace and see if there is a change?

May 22, 2020 | 03:12 PM

Mark Kovalsky

Frmr Ford Trans Engr

Joined: Aug 1999

Posts: 24,732

Likes: 2,661

From: SE Florida

The VSS can be check for resistance. I don't know how many ohms it should be, but it's on this site somewhere. You can also remove it from the differential and see if there is a bunch of metal stuck on it, it is a magnet.

The PSOM isn't a sensor, it is a microprocessor. You can remove it and open it to see if any of the components inside show leakage.

May 23, 2020 | 05:41 PM

John11.25

Mountain Pass

Joined: Dec 2017

Posts: 130

Likes: 21

From: Lebanon, TN

If you determine that the PSOM may be the problem, You can get a rebuilt one from Clusterfix.net, Ford doesn’t sell them.
After replacing the VSS and pigtail, I replaced the PSOM using this company last year. So far it has corrected the shifting issue I had.
I was getting a P0500 code.

Aug 5, 2020 | 10:51 AM

akpolaris2

5th Wheeling

Joined: Oct 2018

Posts: 26

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I replaced the VSS and pigtail. Still an issue. I wet under the dash and looked for the PSOM and rapped on what I think was it with a screwdriver a couple of times. Shifting fine for the moment. Possibly looking for a PSOM next. Rockauto does not carry them..

Aug 5, 2020 | 11:07 AM

DanielT28

Laughing Gas

Joined: Sep 2012

Posts: 1,239

Likes: 104

From: idaho

Quote:

Originally Posted by akpolaris2

Sounds like we are in the same boat. I’m having similar issues.

my speedometer was bouncing from 0 to 90 miles an hour, my overdrive light was flashing, and ABS light was on.

I took my PSOM out yesterday. I had a bad capacitor. luckily I have a friend who works on circuit boards, he replaced it and the speedometer is food once again. But mine overdrive light is still flashing so I’m trying to figure out what’s going on.

what type of vehicle speed sensor did you use? Ithe ones I tried will not work. When I install any other speed sensor other than the one that came with my pick up,the Speedometer does the output speed at all. PARTS store ones or OEM ones from Ford

If you look closely to the right of the black square the capacitor has shrunk or expanded. so the shrink wrap around it Isn’t covering the top anymore