Hey everyone,
I have a 1997 f350 with a 7.3 diesiel. I drove the truck to work and 12 hrs later went to go home and the trans was slipping bad, the ABS light stuck on after going off when I started truck, the od light flashing and no speedometer at all.
I changed the the vss/abs sensor on the rear differential which has always solved my problem in the past but this time did nothing to help. I have checked the wiring, pins in plug and sensor and everything looks good, pulled out the sensor and cleaned it.
I have another sensor I bought that is somewhere on the trans with looks like a square cable that spins maybe for the speedometer.

Does anybody have any suggestions? I did a search and everyone point to the sensor on the rear differential but that is not it.

Thanks in advance

 

The only other thing you can really do that is an easy thing to check would be to check all the brake lights (yeah they can can have an affect on the transmission). I doubt that's your issue though.

Does the speedometer work like it should? Does is hop or bounce up and down as you're driving?

The only other sensor that it could be on the exterior of the transmission is the TRS (Transmission Range Sensor). It is the sensor that tells the PCM what gear the selector is in and it is located on the side of the transmission. You should be able to see it from the ground easily enough.

If the OD light is on, the PCM has stored a code for the transmission. It is like a Cehck Engine Light for the trans. Take it to a tranny shop and have them read the codes. Post those up here and then we will have something to go by. Without the codes, you're just kinda guessing.

 

your psom on behind your speedo also could be your issue i would search this forum for threads on psom, its easy to change, i did mine in less than an hour

 

Speedometer acting normally?

 

I checked the wiring harness again and found both wires going to the vss broken right in half, put them backtogether and good to go again. If it was not for everyones help on this forum allot of us would be out thousands of dollars working on our trucks i am sure. This repair cost me nothing but a little research and a great Ford truck forum.

 

I have the same problems...it started out as occasionally the OD light would start flashing, when I went up a long slow grade never a steep hill. It slowly got worse at times the speedo would bounce and the tranny would not shift properly, and I got an ABS flutter. The other night it ran good to my girlfriends house, when I left it was worse than ever! I checked online what the problem may be and it seems to point to the VSS mounted on the rear axle. Changed it and no difference...although I noticed the wire leading to the VSS was kinda sloppy feeling so Im going to go outside in abit and check it. If that isnt it Im going to look at the tone ring (hope it isnt that) That looks like it could add up to alot of time and money. any other ideas?

 

What code was stored when the OD light flashed? Trying to fix this without knowing the code is going to waste a lot of time and money.

 

The only code that showed it did say a torque converter slipped which seemed odd as the transmision had recently been rebuilt. will the VSS affect my torque converter? I used a POWERCHIP diagnostic reader..otherwise all codes were clear

 

well I went out and checked the plug in on the new VSS it wasnt all the way in...i pushed it till I heard it click, It did still feel a little bit sloppy. Same thing happened when I changed the glow plugs the wiring harness did not fit tight on the aftermarket valve cover gaskets. So being the same harness that runs the injectors it made the truck run a little odd, which I did fix and it ran fine afterwards. Im also going to try and change the oil in the differential. Cant hurt to change the oil as the old VSS looked old and possibly was not sealing...it pulled out very easy and I may have got water in the oil and it could have foamed which may give a false reading off the tone ring. But after pushing in the connection on the VSS it drove 95% better. But still being sloppy I think it may not be getting a good signal.

 

I have been dealing with this for weeks! Please don't tell me I need a trans. ABS light was coming on intermittently but no noticeable issues. Then OD light started flashing and trans began shifting hard and slipping in high gear. Neighbor put his scanner on it, (Snap-On) no codes. Replaced ABS sensor on differential, unhooked batteries, worked for 5 miles and and went back into limp mode.
I cleaned the pins/sleeves on the connector and ran continuity on the wires from the pigtail on the ABS sensor to the firewall connector, both conductors are intact.
Everytime I scan it, it says there are no codes, but it works for a short time after I unhook the batteries and reset the brain. Fluid looks good as well. How critical is the air gap between the sensor and the sounder on the ring gear? I am beginning to grasp at straws here. Don't want to believe that it is a tranny problem, because when I reset the thing it shifts and drives fine for a few miles before it goes into safe mode again. I do have some shady wiring going on with the trailer harness, but that would seem very unlikely. Other than the sensor, what would cause the ABS light to come on in the first place? I am a an electrician by trade, and have been slinging wrenches since I was a kid, all this is greek to me..Should there be 12 volt D.C. power at either the red or green wire on the sensor? Any help?

 

Sketch trailer wiring can cause these kinds of issues as well. I would correct whatever you have going on there (or temporarily disconnect it) and see where that leaves you. As far as the O/D light blinking if it was doing that there IS a code stored, but you may have to take the truck to a transmission shop to have the codes read.

Funny how easy it is to let the things go that are your specialty at work isn't it? I can say that because I was an electrician by trade as well and I HATE working on automotive electrical issues.

 

Still an unknown - is the speedometer working correctly? Yes, the condition of the tone ring in the diff is critical. Crud between the reluctor notches, anything built up on it, even contaminants in the diff lube, can play havoc with the VSS signal. And that's the one thing that's common between the ABS and the tranny.

Unless your neighbor's scanner was an MT2500 (old red brick) with a K2a personality chip, it didn't read the truck correctly.

 

The speedo has always worked, which I also find confusing. I believe he did refer to the scanner as a "brick" and he had several different modules for it (had to dig to find the right one) and when the proper characters from the VIN were entered it brought up all the correct info re the truck.. As to the model number of the scanner, I can't tell ya.

@DIYM: Spot on Brother.. These things drive me crazy. And because I am an electrician, everyone thinks I should be able to whip right through this stuff! (Or fix their VCR's, install stereos, .. LOL! )

Thanks for the input guys..

 

Oh..and the reason I asked about the tone ring/sensor relationship, is because the one I got from NAPA is molded in plastic, whereas the original had a steel mounting tang. When I tighten the bolt, a slight gap develops between the diff and the sensor seat..

 

I can almost promise you are not going to fix this without the codes. You need someone with the right software in their scan tool. Your neighbor doesn't have it. The places that read codes free don't have it, either.