Could this dirty VSS also happen in a 95 F-150 4x4? I also am suffering from the jumping needle syndrome!!!! Mine doesn't start jumping until I hint 40mph range, and it jumps 10 either way above 40mph+.
Does a 95 5.8L 4x4 have a VSS in the rear?

 

David, the most important thing to find out, is if your engine has a dead spot at 2-3 mph where if you drive the truck at a crawl, the engine wants to die. If that happens, then you know its the speedometer. Also, if it's the speedo, it has a pattern to it....at hwy speeds, the needle will jump way past your actual speed, and sometimes hit hte speed limiter and you'll feel the truck's engine start to cut out.

If you don't have a dead spot, and the needle doesn't jump way ahead on the hwy...then most likely its not the speedo.

When you're rear end is loose/worn out....that carrier will move...and when it moves...the speedo sensor can't pick up a clear signal cuz that carrier is shaking in the rear end.

It's not always the speedo, its not always the rear end, it's usually NEVER the speed sensor itself (its a VERY simplistic device that can hardly fail).

So if you have a bouncing speedo, it's either the rear end components are screwed up in some fashion (pull the rear over off and inspect it), or the speedometer in the dash is gone.

The speedos are known to go...its a common thing...ford fixed the problem at some point (not sure when)...like any new one you buy shouldn't suffer the same problem...but always check the rear end components to make sure they're secure and tight. If any gears or bearings are gone in the rear end, which usually happens around the 100k mile mark, then it can cause the speedo needle to bounce.

 

I had the same with my needle. Bought a junkyard special and had the exact same symptoms. I replaced the VSS but that made it worse. You have to make sure the gap between the tone ring and the VSS is only 15-20 thousands. This made a tremendous difference. The speedo still moves but is liveable. I'll be replacing the tone ring when the rear end goes.
Good luck.
Al

 

Well, the tone ring can't have any damage to it (broken or damaged teeth). It's position relative to the speed sensor, is determined by the way the carrier is mounted in the axle. That only goes on one way, and if it's not in right, most likely the bearings are gone on it.

ANY rear end damage can/will cause speedometer issues if the rear end damage affects the carrier's position, or that tone ring.

Also, sometimes the bolts on the ring gear can come loose, if that ring gear is loose, since the tone ring is mounted behind it, it will affect the tone rings position....

All this falls under inspection of the rear axle. If all of the components of the rear end are tight and where they should be....you shouldn't have any speedo problems caused by the rear end. If you've got miles on your rear end and it's sloppy, bearings/gears worn....then that carrer will move (when it's not suppose to) and that'll cause fluctuations in the speedo needle. In that case, the needle fluctuation would indicate that the carrier is moving in the rear end. Moving, as in other than just rotating like it should be rotating. It's held in by bearings on each side, which are known to go around the 100k mile mark.

It's easy to tell which is which just by looking at the speedo needle.

If you see fluctuations in the speedo needle.....look for a pattern. See if you can figure out when it fluctuates, how if fluctuates...etc etc.

A loose rear end, shouldn't have much of a pattern to it, cuz that carrier will randomly move/shake..whatever.

If the speedometer itself is bad, there will be a pattern in the way the needle bounces. When the speedometer is at fault, it has a specific pattern of events that occur. The engine will have a dead spot at 2-3 mph, the needle will sometimes fluctuate 5-10 mph at 20,30,40mph...once your at 60-65, the needle may jump forward between 60-65 and 90-95, you may feel the engine cut out (speed limiter being reached)....etc....

999/1000 times, the actual speed sensor is not the problem. It's just a magnet. It may need to be cleaned off, but it shouldn't need replacing, ever (remember, I said shouldn't...).

If you've got a bouncy speedo needle, and it doesn't follow the pattern I just gave of a faulty speedometer, then your first step would be to remove the VSS and clean it. Put it back in, see if it changed. If not, take the cover off the rear end and have a look see. Most likely, theres somethin' wrong in there.

I hope this clears up any confusion.

 

Tx Justin
Hopefully it's just the speedometer, I need to pry the dash apart to replace some bulbs anyhow. I'll have to pull the cover off the rear, and check that out first though. Sounds like thats the easiest first thing too check out.

 

You can't buy just the speedometer, you've got to buy a whole new gauge cluster ($350) unless you go to the junkie.

If you buy new, the dealer should program it for your mileage and calibrations (just like the old one was).

If you get one at a junkyard, make sure you test it and make sure there are more flashes left in it. Ford lets you change the calibration on it I think 8 times, once those have expired, you can't change the calibration on it. So make sure whatever you buy has some calibrations left. You can also have the mileage changed to your mileage via a dealership. There is another way to change mileage on it, i think with a radio, but I never really learned that way.

We have a tech article (link up top) that explains how to work with this stuff, check out "how to install a tachometer in a 92-96 truck"...or something along those words.

 

Ok, here another question for ya's. How do you remove the VSS for cleaning?
I removed the only bolt holding (only seen the one) that I seen ,and it is still securely attached to the pumpkin.

 

Thats exactly how you take it out, remove the bolt, remove the connector, then pull the sensor out. Must be stuck, try some penetrating oil, see if you can twist then pull...etc

 

Definately sounds like the wheel speed sensor. If you have an E4OD tranny and anti-lock brakes, you should be having problems with them too. The fuel shutoff is probably due to the high-speed cutoff setting in the computer as a result of the faulty speed input. The sensor is about $10-$20 depending on the type you have.

 

A faulty speedometer will also affect the E4OD shifting and anti-lock brakes