1997 Expy OD light flashing, transmission slipping

[webmack]

My 1997 Expedition Eddie Bauer 4x4 5.4L 8cyl (92,000Kms) has started flashing the Overdrive 'OFF' light. I also notice that when the outside temperature is hottest (afternoon ~ 40C + ) going from 1st Gear to 2nd and back to 1st causes the truck to jerk forward as if the transmission is slipping. When its cooler its still there but much less noticeable. The 'OFF' light starts blinking only when I'm well into 4th Gear on the highway and then stays on until I stop. I've just changed transmission oils, engine oil etc. hoping that it might fix the issue but no luck. I've done some research and I'm taking it in to a Ford dealer this weekend, but wanted to get some info so I know what I'm up for. Is it likely to be the tranny is up for rebuilding / replacement? I've also read it could be just a TTC solenoid and this could act up in high temperature.. is this correct? Will a scan give a code that points to the problem? The engine check light does not stay on, so is it still possible to do a diagnostic scan? What's the ideal steps a good mechanic would take to diagnose this?

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[glc]

The flashing OD light means that there will be stored transmission codes. The dealer should have a scanner that can read them - it takes an OBD2 scanner that can read manufacturer-specific codes.

The FIRST thing a competent technician should do is scan the codes and go from there.

Something YOU may want to do in that climate is get an auxiliary transmission cooler.

[webmack]

Right, I've got the car back from the Dealer. Not impressed.

They got a code P1728 which they say is a transmission slip fault. They rang me after getting the code saying they need to pull the transmission down to have a further look into it. I was about to say ok, go ahead when they said if they pull it down, then whatever the cost came out to (whether it was 5,000 Dirhams or 20,000 Dirhams) that I would have to approve it for them to pull it down. Otherwise I would have to tow the car and the transmission which they would not put back in, myself. I just took the car back and paid them the 400 dirhams for the diagnostics.

Meanwhile I think the transmission is getting worse. The slipping once its warm is more prominent. And once I heard a metal on metal clunk when it shifted from 2 to 3. The sound and the jerking movement forward seems to originate from the lower rearend of the vehicle

So I'm not sure where to go from here. I'm looking for a reliable ford mechanic who has dealt with expy trannys before. But could you guys give me some indication of what this code means and what am I likely to be looking at?