I have a 95 F350 crew cab, 460,4X4 with a auto trans, and I was wondering if anyone has had a problem with the speedometer needle jumping around at slow speeds? Mine does this until I get above 10 mph and then it's fine. Anyone out there have any ideas? Thanks, Doug

 

check the sensor on the rear for corrosion or loose wiring...

 

Mine did the same thing in my Ranger..........then the cable snapped.

 

He doesn't have a cable on a 95. You could do a search for "bad PSOM" and find out instructions on what to do, essentially you want to check all wiring for the speed sensor on top of the rear diff, make sure there are no bad wires. Next, remove the speed sensor (1 bolt and it pops out), clean it with a rag, and put it back in. Next would be to pop the rear cover off the differential, and check to make sure the axle is in acceptable condition and that the tone ring for the speed sensor has no damaged teeth on it. If everything checks out this far, it's possibly the speedometer module in the dash that needs to be replaced, it's been known to need replacing from time to time from what I've seen on this site. If your engine starts cutting out and wanting to stall while going 2-3ish mph, it's definitely the speedometer module.

 

Thanks guys for the help. Now I've got a direction on what to look for.
Thanks again, Doug

 

Justin, can you tell me more about this? I get the waving speedometer between 60 and 70, and I have a hesitation just as I first take off but after that the truck runs like a watch. Could the two be interconnected?

 

Hey Mustang, does my 92 have a cable?

 

gatesj - what truck are you talking about?

qman - No, yours has a VSS.

 

You need to replace the speedometer module in the dashboard. You have a bad PSOM (programable speedometer/odometer module). The hesitation just as u first take off, is a clear indication of that. Another indication is the waving speedo needle at higher speeds, I had this exact same issue. When the truck is moving 2-3ish mph, it'll want to die. The reason for this, is because the speedometer module is giving the computer an incorrect speed reading, the computer thinks your going between 130-180mph and shuts the fuel injectors off for the speed limiter for that tight window of 2-3 mph.

Put simply, you need to replace that speedometer in the middle of your dash. For more information, do a search in this forum for "bad psom". I had this issue with my other F-150, and just simply bought a new gauge cluster from Ford, it was $350. If you want, you can go the junkyard route and fetch one, but the mileage will be off (needs to be corrected by a dealership for $50 or so unless you dont care about the mileage being correct), and it will need the correct calibration for the tire size you'll be using. Changing the calibration is very easy, but ford only allows you to do this 8 times before it's not able to be changed, so make sure you buy a dash that has some "flashes" left. There is a tech article on our website in the Tech Articles section which tells you about calibrations on these.


The 92-96 trucks do not use a cable operated speedometer.

 

Sorry about that, it's my '95 F-150.

Justin, I haven't messed with the VSS yet, I was thinking about taking it apart and cleaning it, but the hesitation is always the PSOM, not the VSS, right?

I'm also going to do a conclusive test for vacuum leaks first, those clusters are expensive!

 

DAMN!!!!! Is there anything about these trucks that I WON'T find on this site? SHEEEEESSSHHHHHH!!!!!!! ))

 

No

Yes. A bad VSS signal won't make the hesitation, it'll just make the needle bounce irratically.