Yes.
Yes.
Whatever the codes indicate is causing the problem.

 

Mark, I am hoping you are correct that the Torque Converter is NOT my problem. Here is an update. I replaced the transmission output shaft speed sensor after cleaning and changing differential fluid, drove the truck 20 miles and did not get a flashing overdrive switch light any longer. It had been flashing after ten miles of driving. However I am still getting some slip and over revving. I did find metal filings in the rear end and when I got the truck back home noticed gear lube all over the right rear wheel backing plate. It is obvious I must change the axle seals now. While I have the axles pulled I thought I may as well replace the clutch packs in the differential. I have the 8.8" ring gear, 10 bolt limited slip rear end, 3:55 gears. Just giving you an update and thanking you for your advice. Hopefully this will cure the slippage.

 

I have changed the entire rear axle with one out of a 91 F-150. I had to change the shock mounts, spring perches, output shaft speed sensor and am still getting a blinking OD switch light. The original codes were P0503 and P1500. Both indicate Vehicle Speed Sensor Erratic. I have eliminated slippage in the rear end due to worn clutch packs and speed sensors. Still have the same problem minus slipping in first gear. It overrevs and upshifts around 4,000 rpm, OD light starts blinking then it won't stay in OD.

 

You sure have a lot of energy and some money to burn.
The 503 and 1500 codes are telling you the signal FROM the sensor is noisy or intermittent. It is an input signal to the computer.
It is causing the computer to make the shift changes.
VSS out to the computer, computer back to trans valve body for false shifting due to the noise. The computer program thinks it's a request for some action on a false basis.
The VSS, TPS and engine RPM are the mains shift controls. Any other false signals Fs things up.
It's not the trans, valve body, clutches or converter.
It just happens the VSS is in the rear , signals the computer up front, computer operates the trans in the middle.
Fer-stay?
Fix the noise issue and let other things alone..
Were trying to help but your not being still long enough to put it all together.
Good luck.

 

Did you check for a broken wire/connector or damage in the harness?

 

First I replaced the sensor before the dealer scanned the truck, it was my first suspicion. No change so I had dealer scan it, he said it was metal shavings in the differential throwing the VSS (Actually an ABS speed Sensor) sensor in the rear end off so I completely cleaned the rear end, filled with new fluid and additive, some improvement but still same problem. The clutch pack and axle bearings and seals were all worn bad so I changed the entire rear axle with one out of a '91 F-150 2WD. I cleared all codes and drove it, OD switch light still flashes after 5-10 miles. Today I dropped the pan and found the old filter simply laying in the bottom of the pan. I think I have found the problem. Now my question is: while I have the pan off, is there anything I can check without removing the valve body or going any deeper? The valve body was still tight but the old seal was stuck inside the hole the filter goes in. I managed to get the old seal out without scratching the aluminum, new filter, fluid and some Sea Foam Trans medic going in tomorrow.

 

The filter being loose in the pan is sure a problem. LOL

I don't like transmission additives though. Just an FYI

D

 

Yes I did and did not find anything wrong with the harness.

 

Darrin. I installed the new filter, fresh synthetic fluid and took it for a test drive. Shifting is improved but it still seems it is staying in gear longer than it should before upshifting. Once it gets to third I have to back all the way off the throttle to get it to shift into overdrive, once it does shift into OD the rpm's fall off and it shifts back into third within a few miles. And I am still getting a flashing OD switch light. I am running out of time (and money!) as I live in Louisiana and have a new job waiting for me in North Dakota. I was planning on taking this truck up there to move with if I can get it fixed before I have to leave. I have to get there before the Christmas holidays or I lose the new job and am unemployed. What should I check next? Thanks a bunch!

 

God man, I don't know. Sounds like you have several problems going on. I honestly don't know that I would trust that truck to get you where you need to be. Particularly if it's for a new job that you really need. I think if it were me I would consider selling it I couldn't figure out what all was wrong, nobody local that could get there hands on it could either and I had to have reliable transportation.

Blows me away that someone with a scan tool can't figure it out, but it is what it is I guess. I wish I had more to offer from here, but I don't want to be throwing any more wild geese into the mix from a keyboard in Indiana. Particularly since it's critical that you get it sorted out quickly.

If you're dead set on fixing this and need it done right within that timeframe, I think I would bite the bullet and hand it over to a reputable shop that you trust. Regardless of what you think, it's likely going to cost you less in the long run rather than to be going through what you are now. Different story if this were a truck that you were just playing around with and didn't have to rely on.

I hope it gets sorted out and congrats on the new job!

D

 

Doesn't that truck use a VSS in the transfercase to control shift points?

 

I do not know if there are any sensors in the transfer case to control shift points. I have not done anything with the transfer case at all, it seems to work fine.

 

The Ford Mechanic said it was in the rear differential speed sensor, metal filings were throwing the sensor off. I have not taken it back for a second scan and now I don't have any problem UNTIL it shifts into overdrive. I think I am going to lockout overdrive and put some more miles on it and see what it is doing with OD locked out. Thanks.

 

Since the transmission is totally electric control, it does not make any shift decisions. It's operation is totally from outside of it.
Shifting is all done through the PCM program.
The shift decisions are normally made by the inputs from the speed sensor, the engine RPM and the throttle position (TPS).
On upshifting, where the TPS is advanced with more throttle, the engine RPM is rising and road speed is rising, the program enters a line with a number loaded in that tells the trans to upshift at conditions that exist for the three inputs.
On a down shift, the action is the same but reversed by another program line loaded with a different number, as the inputs are coming downward.
These shift controls are the valve body solenoids that open and close fluid passages and control the pressure applied to the servos and clutch packs.
The TC lockup is mainly by the TPS at cruise under light throttle.
Be awhere that TC lock/unlock is not the same as down shift to third gear.
They are two different actions.
Going back, you can see from this operation, the VSS codes are indicating a noisy unreliable signal as part of the decision making process.
I recently saw another thread with the same issue but don't know the outcome of it.
Granted it is a tough one to crack but don't know any easy way but look for the circuit noise/intermittent problem. It can get involved, takes a lot of time and needs some one who understands what I have described above.
Good luck..

 

What I am saying is
I think the pcm gets it's input from a vss on the transfercase
for the transmission shift points and not the abs sensor at the rear
diff.
I remember reading somewhere that the 97/98 4x4 models only
have this.
Might be worth a look
Good luck