The O/D light flashes it is off

My 1999 Ford Taurus (140,000 miles) is giving me trouble. This usually happens when I have just driven off the freeway and now am driving in stop and go street traffic. The O/D light indicates it is off. The odometer stops working. The needle on the tachometer slowly accelerates. The speedometer remains stuck at zero. The engine sounds like it it straining to work.
I fear that this is going to be an expensive repair; I hesitate taking it to my Ford dealership. My family’s trusted auto repair shop technicians seem perplexed by this problem. They hint that this might have something to do with my turbo engine. Help!!!

This probably is not a very expensive repair. The transmission Power Control Module and the speedometer have lost the signel from the Vehicle Speed Sensor. First trouble shoot the VSS and wiring to determine if the signel is present at the VSS and getting to the destination (the PCM). If the signel is getting to the PCM the problem might be more difficult to trouble shoot.

The PCM commands the shifts and lockup for the transmission so that explains why the transmission is going into ‘limp home’ mode. Part of the ‘limp home’ mode is to turn ‘ON’ or flash the O/D OFF light.

Hope this helps. Let us know what the outcome is on this matter.

The flashing OD light means something, likely a transmission malfunction. The other symptoms sounds like you are in “limp mode” which is the car runs enough to get off the road but is having a potentially serious problem.

Your trusted mechanics perplexity is perplexing to me. A good shop should be able to read codes and diagnose the problem(s), but if no good shop is handy a Ford dealer might be best to at least figure out what is going on. A crank sensor might not be feeding info into the computer for some reason, bad sensor, bad connection, bad computer, etc.

The car is sick and continuing to drive it as is won’t help things. Take it somewhere for a diagnosis and then see where you are when you have a repair estimate.

I am perplexed by your trusted shop too. I have never seen a '99 Taurus that was turbocharged, not the 3.0 L pushrod or DOHC, or the 32 valve 3.4L SHO V-8. If someone added a turbocharger to it, that would be HIGHLY unusual. Have they tried to sell you any blinker fluid?

Get the codes read first before you go jumping into anything. This could be one of several things. Codes are the best place to start. Post back with the code/s and we will go from there.