My speedometer just started jumping a few days ago. I've changed the vss, unplugged and checked the abs module, and visually inspected the speedometer. The new vss didn't do anything. Speedometer, psom, appeared to be ok. Well, nothing seemed to be loose.

From what I read on a previous post at 30 mph I should get 3.5 volts from the abs module. I was getting approximately 3.0 volts, speedo was jumping which made it difficult to tell what speed i was at. Then I unplugged the abs module and at 30 mph I started getting 4.5 volts, speedo was still jumping.

Does this sound more like a module problem or a speedometer? Going to look for replacement parts this Saturday and was wondering what all I should get. Any other suggestions?

In case this helps, its a 95, auto, 4x4.

 

Just posting my results on this. I got my Motorcraft sensor a couple of weeks ago, but just got around to installing it on Monday. My issue was the needle bouncing about 5-10 mph when I got up to about 65-70. I road tested it today, held 65 for about a mile, and the speedo's reading nice and smooth. So, apparently either the Motorcraft sensor is the only one that will work reliably, or my NAPA replacement that I had installed previously was defective.

Both sensors looked the same, except of course the part numbers that were stamped in them. I measured their length with a digital caliper, and they both measured within .005 of each other. I did notice, however, that the center magnet part of the Motorcraft sensor was sunken down, maybe .010" from the outer part of the sensor. Not sure if this is what makes the difference or not.

The Motorcraft part I bought was part number F85DZ-9E731-AB. I bought it at Fast Parts Network - Home

 

I know I’m still new here but I’ll share my experiences with this issue thus far. My speedometer is mostly consistent all the way up to 65. Once at 65 it bounces anywhere between 5-25 mph, but this doesn’t seem to affect anything else (shifting, speed limiter etc). Another thing I’ve noticed is that if it’s under load the bouncing is much worse than when it’s not. Even if I’m coming down from 65+, it seems to level out sooner but if I jump back on the throttle it begins bouncing again. I replaced the VSS (Autozone calls it a rabs sensor) with one similar to what’s pictured on the first page and the issue began occurring at 50 mph instead of 65 so I swapped back. My abs light is on almost full time now as well. I’ll unplug the module this evening to see how that affects the issue and I’ll report back.

Thanks for all the info!

 

So I'm straight, this is the part number for a new Motorcraft VSS, which fixed your problem after you replaced it and plugged in the RABS box again? I tried searching that part number and couldn't get it to come up.

 

Yes, this is the part number that was on the box for the VSS that's mounted in the rear diff. Try searching without the dashes maybe? There was another number on the box as well, DY-1123.

I haven't plugged the RABS module back in, not sure how that will affect things.

I did, however, have a chance to get the truck on the highway today. Speedo stayed nice and steady, got the truck up to 80 MPH.

 

Welcome to FTE! There's a lot of great info and great people here. Let us know how you make out, hopefully it's something simple!

 

Thanks for posting your results. I think I am going to order one of them.

 

You're welcome! Hope it works out for you.

 

After unplugging the RABS box behind the glovebox, the speedo held steady all the way up to 75 and appears to be in good working order again. Thanks for all the info guys!

 

That's what worked on mine, smooth all the way up tell it stops. Lol, and no ill effects with the brakes and no cel. I found it odd something likethat could affect it that much.

 

Hey guys, I'm new to the forum, but came here to find some answers. I'm having the same problems and was just wondering if anyone had any problems remaining after replacing the VSS with a motorcraft one and plugging the RABS back in.

 

Anyone have any T/C shudder while the speedo is bouncing? Maybe I have a different issue.
I haven't found anything about a bad T/C causing speedo bounce yet.
I've changed fluid/filter and vss (the second listed one from advance) but still bounces around 50mph. It only bouces 2-5 mph from 50-60mph depending on accelleration.
From all i've read this week i'll check my trans filter installation and rear tone ring condition.

97 f250 psd e4od

 

I don't think that the speedo needle bounce is related to torque convertor shudder. Are you sure thats what is happening?

 

Hi guys, first off just want to say thanks to all of you that have posted stuff on this issue. It saved me a lot of time and money. I just wanted to post what all I went through along with the results to further help out.

I have a 96 F350 with the 460 and manual transmission. So this is what happened. I first started having problems with speedometer jumping and the engine wanting to stall at 1-3 mph and between 70-80 mph. Thanks to the forum I found what was causing this. It was a bad PSOM. I guess it was sending a bad reading, causing a whole bank of injectors to shut off. Anyways, I got this replaced along with the speed sensor (VSS). The main problem was gone but my speedometer was still bouncing +-5 mph. This was caused by a NAPA speed sensor. I replaced this with a Motorcraft one and my speedometer quit bouncing. Everything's working good now. Thanks again for all the helpful posts.

 

well i unplugged my abs (behind the glove box) and nothing changed. I've only had the truck a few months but last month it wouldn't shift into first or second until over 2500 rpm's when the trans warmed up so I changed the fluid and filter and added a third cooler. now it shifts fine but i'm getting speedo bounce and some sort of shudder similar to clutch chatter. If i turn on the hazards (to unlock the T/C) or turn off the OD it goes away. It's always at 52mph under normal accelleration in OD so i don't think it's the vss or toner ring maybe the speedo but I can't find the connection between the shudder and speedo bounce.
Next thing i check is the trans filter.