First off, I would just like to thank everyone on this forum. All the helpful posts, all the little tips and write ups and pictures have helped with some troubles I have had on my 95 XLT. Thanks to everybody.


My issue at hand is the notorious bouncing speedometer. I have changed the vss on the transmission, the differential sensor, checked wiring and connectors(all were cleaned and unbroken), tried a few different psom's(all different years ranging from 92-96), and even tried a couple different rabs modules(as I've heard the psom is tied to that somehow). speedo still bounces.


I replaced my front brake pads earlier this summer. Shortly after I began getting a pulsing in my brake pedal. So I unhooked my rabs module and no more pulsing. Also noticed my speedo bounce range went from 10-15mph to about 5. While I was under the truck changing the differential sensor, I noticed what I believe is a chassis ground, was broken. I found three and all three are broke. I have pics attached to verify that they are chassis grounds. Would these broken grounds affect the speedo at all? How would I go about replacing them? Thanks in advance for any ideas or suggestions

 

Bad grounds will cause problems, yours specifically: you won't really know until you fix them.

Just get some wire and eyelets, crimp/solder the eyelet to the wire and replace. Take it as far back as you can if you aren't able to remove/replace the entire ground wire. Also be sure to clean up the frame around the bolt, replace the bolt as well. $0.15 for a new stainless bolt is a lot easier than trying to clean up the old bolt.

When you replaced the dif VSS did you clean up area it mounts in? It has to read the speed ring through the metal and any extra interference will cause issues. I would also check your wiring starting at the dif VSS up to the PSOM in the cluster, clean all connectors with quick drying electronic clean, check for loose pins, damaged wires, loose connectors, etc...

 

Thanks fltdriver. Its been pretty chilly here in WI, im hoping for some sunny weather this weekend so i can get under there to fix.

As for the diff vss, wiped the area clean of any old sludge like fluid and debris before installing the new one

 

Definitely the grounds need fixing, but a booster cable from the frame to the cab would tell you if it's your problem for sure or not.
The Vss in the diff, that's one of those sensors where most people say Motorcraft only.

Also since you seem to have tried everything else, I believe there may be a speed sensor on your transmission as well that's tied into that system. And I think the cruise control might be too.

 

Im gonna go ahead and pay the extra money this time to try a motocraft sensor. Ive never had issues just going to autozone and using a sensor i buy from there, but theres a first time for everything.

As far as the grounds, im gonna remove the wire thats there and go with some 4-8 gauge wire for my grounds.

I'm also guessing the cruise control is tied in some how cuz my cc doesnt work. I've always had the assumption it didnt work cuz of the speedo. Is that possibly flipped where the speedo is bouncy due to an issue with the cc?

 

Question: Does your horn work?

 

Yes my horn works. I had to replace the low tone one because when i swapped the fenders i noticed there was a hole melted in it and wasnt working. Replaced and high and low tone both work fine

 

Try unplugging the cruise control. Worth a try.

 

I will try that this weekend and post back. Thanks for all the helpful ideas.

 

I asked about the horn because when the air bag clock spring goes out you lose cruise control and horn.