Okay, so I have tried to do some searching and figure out what my issue is, but I have decided that another thread is best.

So, here we go.

I have a 1993 F350 460. I have had it for quite a while now and the speedo has always jumped. Never much cared, just lost cruise control because it was all over the place.

Fast forward. My brakes were starting to fail so I got them replaced at the dealership. Let me rephrase this, the brakes worked great, they just were starting to make noise and since I didn't have the time (or the special spindle socket of the D60) I took it to the dealership to get them taken care of.
When I picked the truck up I immediately noticed that the pedal was soft and that the truck didn't stop as well as it did before. I called the dealership and they said that the pads and shoes hadn't set yet. Okay, if you say so. Well about halfway through the day the ABS light comes on and I call again. They tell me to bring the truck in. I brought the truck in and they finally told me that my ABS computer(?) was bad and that they were no longer available. Hmmm. Seemed to work 100% perfect prior to my bringing it in. My pedal is super soft, especially at speed, but if I am doing a couple miles an hour the dang thing will practically put your head through the window and will hang a wheel. Something is up.
Also, right at the same time I noticed that my remote start no longer works. Seemed like a different issue to me, so I didn't bring it up to them. I took the truck into the stereo shop that installed my alarm and after having it for a week they finally figured something out. The taillights were coming on when the key was turned, just slightly. They were getting some low voltage from somewhere/something (the tech told me the voltage but I can't remember) and that voltage running through the system was tripping the remote start kill that is supposed to kill it the remote start function when you press the brake pedal and start to drive off. I told the tech of the issue with the ABS light he said that they have to be related.
So after a ton of research I decided to replace the VSS (with an aftermarket unit). EVERYTHING GOT WORSE. The speedo was jumping all over the place now, not just around 70. The pedal was gone, but then a minute later it was all the way at the top and impossible to push. Then the brakes wouldn't release, then back to the way it was before. They were all over the place so I put the old unit back in and got back on the forum to search, no ideas.

What the hell is going on here? Anyone?

 

No one can help with this?

 

Hey there. Sounds like you have air in the lines with the pedal being soft and the RABS light coming on. I'd bleed the entire system (including the RABS valve) then reset the controller and see how she does.

The tail lights glowing sounds like a separate issue which we can tackle later BUT it may not be since the RABS controller is also wired to them.

Does the RABS light flash? If so, it's giving you one or more fault codes which you need to write down.

 

No flashing. I am willing to bet that the taillights are the same issue somehow, too coincidental that the remote start stopped working (taillight issues) at the same exact time that the brakes turned to poop.

I'll try re-bleeding the system.

 

Unplug the RABS module, located behind the glovebox. It is in the signal path of the VSS to the PSOM/PCM/Speed Control module. Many times a faulty RABS module can pull down the VSS signal before it gets to the PSOM. See if your speedometer bouncing disappears.

 

I was going to try that, but I couldn't figure out what module is the RABS. Are there any pictures of one somewhere?

 

Good call Randy, I completely missed the bouncing speedo part of his post. The same thing happened to me when I first got my 96... same cure too.

OP, to get to the RABS module you just empty out your glovebox, squeeze the sides in and let it drop onto the floorboards. Look straight back and roughly centered in there you'll see a black rectangular module about the size of a paperback book.

I also still think you have air in the lines with that soft pedal.

 

A nice photo from the web:

 

I am leaning towards more than one problem too.

 

So I pulled the RABS and the needle is not bouncing, BUT all of the other issues remain. Brake lights are still drawing small current and on when the ignition is on, but no lights on.
Thanks for the help identifying the RABS, believe it or not, I actually did a google search for the picture a few days ago, but wasn't able to find for certain which it was. From what I understand the RABS is no longer sold new, so I guess it's off to the Pull-a-Part to solve at least one issue.

I am going to take the truck back to the dealer and make them bleed the whole system. Maybe that will solve the pedal and braking power issues.

I was thinking that the current draw for the brakes lights might be from the brake light switch at the pedal, but the car stereo tech said that he unplugged it and got the same thing. So I guess I'll keep thinking about that one.

Gotta love old trucks. (now if I could just find a steering column for my '64)

 

Sounds like a bad body ground and something is grounding through the tail lamps.
Check the body ground at the fender by the battery.


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I thought it might be the LED bulbs, but the stereo shop tech tried regular bulbs and they lit up too. I do know that the battery terminals are band new Monster units, but I haven't checked the body connection. I'll look to see what I can find.

 

I don't know if this narrows it down at all, but I just drove the truck and if you hit the brakes while going less that 5mph the rear wheels lock up immediately. The RABS is still disconnected

 

Oh, and the fender ground seems great. No wiggle, no nothin.

 

Oh, and the fender ground seems great. No wiggle, no nothin.