That would make sense. I was recommended to use red lock tite on the bolts.

you can see some scarring on the carrier. I would bet you are right and that’s why it was welded as well.

 

The ring arrived today. I got everything put back in. I’ll put oil in it tomorrow and test to see if the problem is fixed.

it definitely looked like the bolts backed out of the carrier. I found pieces of them in the oil.

 

I got home today and put the oil in and then while the truck was still on stands I tested it.

The speedometer finally worked as it should and naturally the truck ran and shifted as it was intended.

However when I went to brake the rear wheels wouldn’t stop.

I then conducted another test and unplugged the module behind the glovebox and then ran the truck and braked it. The brakes worked as they were supposed to.

so based on that is it safe to assume that RABS module is bad and needs replaced?

 

The RABS hydraulic unit on the frame rail is ok. The RABS module/computer in front of the glove box is bad.

 

Any recommendations as to where to get one?

 

 

I found a new old stock module on eBay and threw it in. Problem solved.

Turns out the whole system just needed replaced. Real cool haha

thanks for all the help.

 

Thanks for the update. Just for prosperity, what was the problems and what did you do to fix it?

 

Good point!

So here is some context on everything.

I bought a 1996 F350 4x4 cab and chassis truck with 104k miles on it with the 7.5l.

When I test drove it, it ran rough, shifted unbelievably hard, the speedometer violently jumped everywhere throughout the entire range of the dial and didn’t brake well at all.

I didn’t know much about these trucks and just thought it was a simple fix by replacing the VSS.

When I got home and did a little research, along with advice from this forum I realized it could be a lot of things.

I sent the PSOM down to Module Mechanics in Colorado and had them rebuild it. I put that back in and it fixed most of the issues. It ran better and shifted as it should. However the speedometer jumped around still. Not as bad but still didn’t operate as it should have.

When I was in the process of replacing the VSS I saw the plug to the sensor was melted and thought maybe it was that. So I replaced both the sensor and pigtail and no change. I read where people said that if they aren’t grounded correctly you will have a jumping speedometer issue. I cleaned the rust and made sure it was grounded and again no change.

In order to test it I had it in my shop on Jack stands. I would put it in gear and let the back wheels spin and watch the speedometer. When I did this I found that my rear brakes wouldn’t engage when pressing the brakes. I had to put it in neutral and let it coast down and then right at the end it would grab and you would feel it in the pedal. I unhooked the module behind the glovebox and tried it again and the rear brakes worked indicating the module was bad.

I pulled the diff cover off and saw that at some point a few bolts came out of the carrier and the tone ring was welded to the carrier and the ring itself was damaged. I replaced the ring and made
sure all the bolts were in the carrier and I put lock tight on them.

I tested it again after the differential was assembled and the speedometer operated as it was supposed to.

I ordered a RABS module from eBay that was new old stock and put it in and then again lifted it on a Jack and put the truck in drive, let the rear wheels turn and then brake and they worked as they were supposed to.

In the end I replaced the PSOM, the VSS and pigtail, the tone ring and the RABS module which in my opinion they all needed fixed outside of maybe the VSS itself.

Now I’m off to fixing some other issues and gremlins this thing has.

 

I was on my way to town today and my truck was driving fine at 70 with the cruise on. The speedometer started doing its jump around thing and the transmission shifted to drive and then the speedometer quit followed but the ABS light coming on and the overdrive button light flashing. The transmission was shifting very hard.

i checked the fuses and they were fine. I turned off the truck and turned it back on and the ABS light went away and the overdrive light on the shifter stopped flashing and everything was normal except still no speedometer.

I replaced the VSS and again no change.

So I guess ill stick a camera in the rear end to
see what the tone ring looks like.

Any ideas again?

 

Check your ECM out. They tend to have issues at this age. You can open them up and check iut the board. When mine went out it was flashing the OD light. Ended up getting one from napa.

 

Turns out the tone ring came off the carrier.

I guess I know why the previous one was welded on.


Unless anyone has any other ideas on how to keep this from happening again I guess I’ll have to pull the carrier and weld the ring on so it won’t walk off.

 

Atleast you found the smoking gun.

 

no kidding I’m hoping I can get it back on in the morning without having to pull the carrier.

 

Not quite the smoking gun I was hoping for.

I was able to get the ring on and I tack welded it in.

Speedo works fine to about 50 and then is all over the place. Not sure what the issue is now.