Wild speedo
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Senior User
Joined: Jul 2009
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From: Bellingham, WA
Wild speedo
Ok guys, I've read some threads here and I'm still at a loss on this one.. My speedo will bounce like crazy during driving... Sometimes no movement at all.. But never readable or any where near accurate... I noticed today that it also was bouncing wildly at an idle, not in gear..? Any ideas would be greatly appreciated
Lead Driver
Joined: Oct 2003
Posts: 8,476
Likes: 37
From: Madison, WI
No surprise that the speedo acts as it does whether at idle or in gear. The sensor (VSS) is on the differential, not on the transmission. If it were tied to what gear you were in, the speedo wouldn't work in neutral, even when it works normally. That's why it's on the diff. It's also the prime suspect in this case. Either the sensor itself is bad, or built up with metal shavings (it's magnetic), or what can also happen is that metal shavings will build up on the notches on the tone ring (the thing the sensor "reads") inside the diff. Remove and clean, inspect the tone ring thru the hole, try again. If it still bounces, replace the sensor. If it _still_ bounces, you may have to open up the diff.
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Senior User
Joined: Jul 2009
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From: Bellingham, WA
I plan on inspecting the vss tomorrow after work.... Hopefully, but just to be clear when I say idle I meant the truck was not moving what soever.. It was just sitting out front of my house running... Thanks for the tip though, I will be inspecting the vss
Lead Driver
Joined: Oct 2003
Posts: 8,476
Likes: 37
From: Madison, WI
Ah, I thought you meant you were coasting. But come to think of it, since it's magnetic, if either the sensor or the tone ring (why don't they just call it a "reluctor", like it is everywhere else?) is ooked up with metal shavings, I could see how that could "tweak" the sensor even when you're not moving.
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Senior User
Joined: Jul 2009
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From: Bellingham, WA
hey chase been doing alot of reading and came across an old thread i think was you that posted, a "reset" deal for the speedo.. involving holding the reset button and turning the key to the on postion. making the needle peg and go back to Zero.. well i did that and it did just that.. peg the speedo and returned to Zero.. got a code on the odo. E 08 5 if i remember right.... sorry been a long day and just remembered to post this... anyways does this still point to the psom... which sorry to say i don"t fully understand what it is and where is it...
sadly i didn't get to looking at the vss today either.. any other info to aid my search would be greatly appreciated! thanks to all!!!
sadly i didn't get to looking at the vss today either.. any other info to aid my search would be greatly appreciated! thanks to all!!!
Hotshot
Joined: Jul 2003
Posts: 12,177
Likes: 40
From: Newport, WA
No clue on the code, but its probably just a calibration code.
If you were searching I'm surprised you didn't find one of my bazillion posts already
PSOM (programmable speedometer/odometer module) is a small module that is integral to the speedometer (IE, you can't take it off, its built in). It receives the speed signal from the VSS and forwards the info to the PCM, which in an auto trans truck the PCM uses to control the trans. If you have a bouncing speedo in an auto truck, the PCM goes gonzo trying to figure out what's actually going on and it really beats on the trans. The only way to test the PSOM is to swap in a known good unit from another truck.
The PSOM also stores the mileage info, so if yours is bad and you swap out the cluster or speedo portion of the cluster whatever miles the donor rig had will show on your rig.
If you were searching I'm surprised you didn't find one of my bazillion posts already
PSOM (programmable speedometer/odometer module) is a small module that is integral to the speedometer (IE, you can't take it off, its built in). It receives the speed signal from the VSS and forwards the info to the PCM, which in an auto trans truck the PCM uses to control the trans. If you have a bouncing speedo in an auto truck, the PCM goes gonzo trying to figure out what's actually going on and it really beats on the trans. The only way to test the PSOM is to swap in a known good unit from another truck.The PSOM also stores the mileage info, so if yours is bad and you swap out the cluster or speedo portion of the cluster whatever miles the donor rig had will show on your rig.
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From: Bellingham, WA
i'm hopefully gonna go junk yarding this weekend... work permiting, being that i have a manual im sure i need to find the correct cluster..or can i swap things around and make a auto work? also can i get one out of a bronco or any ford truck my yr or yr range? thanks for the help
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Lead Driver
Joined: Oct 2003
Posts: 8,476
Likes: 37
From: Madison, WI
Gasser cluster will probably not work. Obvious differences are fuel gauge callout and tach range. Gauges themselves are probably calibrated differently as well, and the pinouts might not be the same. I can check the EVTM tonite. Somebody did swap in just the speedo from a gasser, a Lightning to be exact, just to have a 140MPH dial.
Only difference between an automatic and manual cluster is the little callout for the tranny. It's just a liitle mechanical needle on a cable. If you get an auto cluster you should just be able to take the little panel off your existing cluster, that covers up where it would say "PRND21", and put it on the auto cluster. Or you could confound your passengers and just leave it there, and make them wonder why you have an automatic shift pointer on your manual truck.....
Edit -- UPDATE; checked the EVTM, and the pinouts are the same for gasser and diesel. Can't say whether the gauges will sweep properly, if you go this way. Oh, and disregard the "Unleaded Gasoline Only" admonition on the fuel gauge....
Only difference between an automatic and manual cluster is the little callout for the tranny. It's just a liitle mechanical needle on a cable. If you get an auto cluster you should just be able to take the little panel off your existing cluster, that covers up where it would say "PRND21", and put it on the auto cluster. Or you could confound your passengers and just leave it there, and make them wonder why you have an automatic shift pointer on your manual truck.....
Edit -- UPDATE; checked the EVTM, and the pinouts are the same for gasser and diesel. Can't say whether the gauges will sweep properly, if you go this way. Oh, and disregard the "Unleaded Gasoline Only" admonition on the fuel gauge....
Hotshot
Joined: Jul 2003
Posts: 12,177
Likes: 40
From: Newport, WA
Gasser cluster will probably not work. Obvious differences are fuel gauge callout and tach range. Gauges themselves are probably calibrated differently as well, and the pinouts might not be the same. I can check the EVTM tonite. Somebody did swap in just the speedo from a gasser, a Lightning to be exact, just to have a 140MPH dial.
Only difference between an automatic and manual cluster is the little callout for the tranny. It's just a liitle mechanical needle on a cable. If you get an auto cluster you should just be able to take the little panel off your existing cluster, that covers up where it would say "PRND21", and put it on the auto cluster. Or you could confound your passengers and just leave it there, and make them wonder why you have an automatic shift pointer on your manual truck.....
Edit -- UPDATE; checked the EVTM, and the pinouts are the same for gasser and diesel. Can't say whether the gauges will sweep properly, if you go this way. Oh, and disregard the "Unleaded Gasoline Only" admonition on the fuel gauge....
Only difference between an automatic and manual cluster is the little callout for the tranny. It's just a liitle mechanical needle on a cable. If you get an auto cluster you should just be able to take the little panel off your existing cluster, that covers up where it would say "PRND21", and put it on the auto cluster. Or you could confound your passengers and just leave it there, and make them wonder why you have an automatic shift pointer on your manual truck.....
Edit -- UPDATE; checked the EVTM, and the pinouts are the same for gasser and diesel. Can't say whether the gauges will sweep properly, if you go this way. Oh, and disregard the "Unleaded Gasoline Only" admonition on the fuel gauge....
Thread Starter
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Senior User
Joined: Jul 2009
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From: Bellingham, WA
So the speedo head can cone out of just about any ford from 94 to 99 or do I need a specific yr to just swap the speedo head? I pulled my cluster out quickly before dark I'm not sure yet how to seperate the speedo part from the rest of the cluster.. Any more info would be great
Thanks
Thanks
Hotshot
Joined: Jul 2003
Posts: 12,177
Likes: 40
From: Newport, WA
So the speedo head can cone out of just about any ford from 94 to 99 or do I need a specific yr to just swap the speedo head? I pulled my cluster out quickly before dark I'm not sure yet how to seperate the speedo part from the rest of the cluster.. Any more info would be great
Thanks
Thanks
Any speedo from 92-97 should work. One from a lightning truck goes up to 140mph
I'd sell the complete cluster out of Whitey if you're interested, 168k miles and change.
Tuned
Joined: Sep 2011
Posts: 416
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I pulled the speedo from a 94 gasser and it worked fine 
I also have a full cluster from a psd that everything works fine if you need one! I found the gasser speedo before the psd cluster got to me in the mail so now I have a spare
I also have a full cluster from a psd that everything works fine if you need one! I found the gasser speedo before the psd cluster got to me in the mail so now I have a spare
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