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I recently acquired a 1996 F350 4x4 DRW cab and chassis with the 7.5 and E4OD 104k miles.
When I test drove it it ran rough, shifted awful and the speedometer was all over the place. The needle bounced violently.
I thought it would be a simple fix so I bought the truck. Needless to say it’s not been easy. I have poured through the forums and the google and YouTube and I have done several things and no dice.
So far I have had the PSOM rebuilt which in fact helped it run and shift so much better but the speedometer is still dancing. I replaced the VSS to include the pig tail and made sure it’s grounding and unplugged the RABS box. So far nothing has fixed it.
I plan on looking at the tone gear to see what it looks like but was wondering if anyone else had any ideas.
I read about jacking it up and running it and checking the voltage and may do that.
a service buliten I read said to do a bunch of stuff to include changing out the instrument cluster which I did as well.
You're completed all the normal steps to fix the vss system.
I'd suggest finding an original Ford Vss sensor and installing that, even if it's used.
Next, buy a cheap 40 dollar o-scope and watch the raw vss signal by using the test port by the driver side hinge.
If that signal looks clean, disconnect the cruise control servo by the driver side hood hinge use the connector to watch the conditioned vss signal coming from the PSOM.
You'll find something not working right. It might be interference from an aftermarket part injection noise into the vss system through induction, or corroded wires.
I got some time this weekend and wanted to try a few other things.
one thread said that it’s possible it’s a grounding issue. So I cleaned the sensor and the bolt up and tried it to no avail. I then thought maybe it wasn’t clean enough so I put the truck on Jack stands and after running a grounding wire to it I put it in drive on the Jack stands and nothing changed.
As I was going to press the breaks to stop it and put it back in park I realized that the rear breaks weren’t working. I put the truck in neutral and let it coast down and as soon as they were almost stopped I could feel the peddle pulsate like the abs was working and then they would work.
Any idea what the deal is with that? RABS module?
I then went and removed the diff cover to check the tone gear and saw this nonsense.
Outside of the fact that it’s flippen welded on there it looks like the tone gear is too big or maybe the carrier is messed up.
The RABS system in these trucks can only reduce brake pressure; it can't add brake pressure. The pulsing you were feeling was just the shoes dragging on the drum because they're slightly out-of-round. More concerning is "why do you not have working rear brakes"?
Unfortunately, your ring gear is toast. If you have experience setting up gear-lash in differentials, you could just disassemble the carrier and replace the ring gear, but most people don't have the tools or expertise to do that kind of work. And I bet that empty ring gear hole is stripped out.
Easiest thing would go to the junk yard and pull a complete rear axle for your truck. You're looking for a dually 10.25" Sterling/Ford full floater axle with 4.10:1 ratio out of a 1992-1997. Bonus if you can find one with a limited slip.
I’m not sure if I’m explaining this correctly but If the RABS can reduce brake pressure that would make sense as to why I press the break peddle and it doesn’t engage the back brakes. Am I wrong here? The brake peddle then pulsates when they finally engage when they are almost slowed down. The pulsating and the noise are what you would see and feel if ABS is engaging.
I just purchased the truck so trying to fix its issues. At this point I’m very glad I hauled it home on a trailer rather than drove it.
The diff cover does not have a drain plug in it so I’m guessing it’s a 10.25 sterling?
You are correct. I can do a lot of things but I am not very good at the axle stuff like that so I will most likely just need to have someone do it for me.
The RABS actuator may be the cause, but you would have other issues. The unit has 2 valve. When the computer senses the rear brakes lock up, it actuates the valves. One valve traps the fluid, and the other valve meters fluid and pressure into an accumulator.
Can you bleed the rear brakes? If you can bleed them, then the isolation valve is open like it should be.
Do your brakes feel spongy? If not, then your accumulator valve is probably closed like it should be.
Okay thank you. I will look at the breaks as soon as I get this diff issue taken care of.
I was in the junkyard last week pulling instrument clusters and found a 92 f350 single cab that is two wheel drive.
I presume that it has the same 10.25 that I need. I’m going to see if it does and what gears are in it and see if I can get the carrier out of it. It had the idi diesel in it. Not sure if that matters when it comes to open or limited diffs. The truck is an XL package.
Since you have the cab and chassis f350, you got the higher capacity rear axle. Normal f350 dualies had axles rated at 1000lbs less than yours. This may not matter depending on what you're using your truck for.
Swapping out the carrier will allow you to keep your heavy duty axle housing, but you'll have to go through the procedure to re-set it up. And you'll need a case stretcher, which is a unique piece equipment, just for assembling axles with integrated 3rd members.
According to your axle tag, you have 4.10:1 ratio with a limited slip.
I pulled the carrier out tonight and it looks like they took the old tone ring off and welded the current tone ring on. It looks like the tone ring is the wrong one and is bigger in diameter than it should be.
I think it’s possible to get the current one off and put the correct one on.
The two missing bolts are very odd. Try removing one of the other bolts and threading it into the empty holes to ensure the threads are still good.
I don't see why that ring gear wouldn't work. You might just try ordering a complete carrier with the ring gear off eBay.
You'll need to remove the ring gear bolts and tap the ring gear off the carrier with a soft face hammer. To reinstall it, you'll need to heat up the ring gear to about 250° to drop it back on the carrier and quickly reinstall the bolts.
I did what you said this morning and the ring gear is good. I too am puzzled by the missing bolts but I wonder if it was because that is where they welded to it?
It's not uncommon for the ring gear bolts to back out and then get eaten up by the ring gear and pinion. It usually destroys both of them. In your case, it looks like the tone ring caught it and got damaged.
Usually, there's a sheet metal keeper tabs that prevent the bolts from backing out. I don't know how the 10.25 does it. I've also seen people loctite their ring gear bolts in place. I would investigate the tabs if I were you.
