1995 F-150, 2WD, 4R70W transmission, 114K miles.


I "inherited" this truck with several issues, but am focused on the XMSN for now.


First time I drove the truck the XMSN didn't try to shift from 1st to 2nd until very high engine revs, then disengaged with the OD light on the shift lever flashing rapidly. I found the fluid was 1 1/2 qts overfilled, and drained/corrected that issue. I checked for any wire/plug/connection obvious issues and found none. Drove it for about 20 minutes, still did the same thing intermittently, but no flashing light. Checked codes and got these:


Engine Off;
172= Oxygen sensor not switching - system is or was lean - Single, Right or Rear HO2S - Fuel control
...maybe from the oil bath it [O2 sensor] gets from the leak?
...and I don't think it's relevant to the shifting issue.

Engine On;
129= No MAP or Mass Air Flow sensor change during "goose" test - MAP MAF
167= No Throttle Position sensor change in "goose" test (must get at least 25% rotation) - TPS
632= E4OD - Transmission Control Switch (TCS) should be cycled once between engine ID and Goose test


Yesterday I drove the truck for about 170 miles from the other side of the state to my house. During that drive, in the first 60 miles or so, the transmission did the "shift disengage/engine revs" thing several times. The transmission would eventually re-engage with a slight jerk, after about 2-5 seconds. The longer it drove the less that happened, only twice during the last hour of driving.



I'm sure this is some sort of electrical issue. Most of the drive the truck ran strong and smooth.

 

Do you know for certain the truck has a 4R70w or are you going by what you were told? What is the trans code on the drivers door pillar? When engine does the truck have?

Are there any issues at all with the speedo or ODO? The shifting issue is a classic symptom of a speed input problem at the PCM, that signal originates in the rear axle VSS but passes through the PSOM before continuing to the PCM and that is why the speedo cluster can sometimes hint at the source of the problem.

 

The flashing OD light indicates that the PCM found a problem and stored a code in memory. That code will stay in memory for about a month unless you clear it.
None of those codes will make the OD light flash. There are more codes stored, and you need those to diagnose this. That means you need a better scan tool.

 

No issues/malfunctions noticeable with the instrument cluster other than the right turn signal dash bulb is burned out. All the exterior signals are working.


Mark,
- The "flashing OD" was only the one time (over a year ago) before I corrected the fluid level.
Do you think a parts store "free scan" likely be able to draw the codes? Honestly, all I did was the "count the flashes" scan, as I was 30 miles from anything when I checked it. Now that I have the truck at my house instead of on the other side of the state, I'm hoping to resolve this issue.

 

Codes that were set a year ago are no longer in memory.

I know that the free scans cannot read these codes.

The light will flash on/off for as long as it detects the problem. It does not flash out the codes.

 

The auto parts stores around here don't even have the OBD-1 scanners anymore for the free scan. I got mine on line for $27.
If you already have a code for bad TPS, I would change that. Mine wouldn't 1-2 shift til 40 or 45 MPH or so, then slam into gear. Then if I touched the gas, it would downshift; may be the "letting go" you sensed. New TPS fixed it.

 

* the flash count codes were for the OBD- wire short, count dash flashes method.


Local parts place said they could read the codes when I called, but "no we can't" when I got the store.


Local general repair shop manager said transmission symptoms "shift flare" are likely from worn seals. ? Recommended a transmission shop if a dose of "trans x" did not help... again ?

 

Update:


After more reading I sent the PSOM/cluster to be repaired. There were intermittent odd light issues with it. Several faults were corrected in the PSOM, but did not resolve the "de-coupling transmission" issue. At least the PSOM is eliminated as the issue.


This will likely end up being a "shop" repair sometime in the future. When time and $$ allow.


When this gets repaired the truck will be an "ace", with all new brake rebuild, good A/C, nice paint/no rust body, and low miles.

 

The 3 codes you got from the 2nd part of the test indicate you just didn't hit the gas pedal while the test was running.

 

Still frustrated.

The truck is at a local XMSN shop (recommended by several other "general" shops). When I dropped it off the guy said it sounded like it could be the neutral safety switch?

After two days, he says (each day) "I drove it for a few minutes and can't get it to do anything." I replied that it is intermittent, but always happens within 10-15 minutes of driving time. He says he can't be out of the shop for 15 minutes.

The best description I can make is, like if you were driving along with a manual transmission, and pushed in the clutch pedal for a few seconds, then released the pedal/re-engaged the clutch.

Is this really that hard for an expert to figure out?

 

Did you ever change that bad TPS?

 

It is hard to figure out. I was researching this very thing when I was at Ford. I had a vehicle instrumented to document everything, trying to find out why it did exactly what you are describing. A coworker and I drove 500 miles one day looking for the problem. It didn't happen. We gave up and headed back. Just before turning into the parking lot it did it! We captured the data and proved that the Transmission Range Sensor (TRS, or commonly called the neutral safety switch) had erroneously indicated that the shifter was moved to neutral.

I recommend changing your TRS. That almost certainly will fix it.

 

SubFord,

Ashamed to say, no. I have the part. Is it really likely at steady speeds that could affect the xmsn?

 

It certainly can't hurt. Thank you very much!

I'll post results...

 

It is possible but I will concede to Mark as he know the transmission.
If changing the TRS does not do it then I would change the TPS.