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Vincent, Ford Senior Master Technician
Category: Ford
Satisfied Customers: 1450
Experience:  28 years as Tech.
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I have a 99 ford taurus, and the transmission shifts ...

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I have a 99 ford taurus, and the transmission shifts in and out of overdrive at cruising speed. I checked the resistance between the two terminals of the tcc and got 20 ohms, which is within reason. Checked the continuity between the two terminals and the battery and none. So it sounds like to me the tcc is good, just wondering where my next move should be, or is there somethings else with the tcc?

The tcc controls the converter lockup not Overdrive. By the symptoms that you are giving me I would lean on the Manual Lever Position Sensor. It is mounted on the top of the transmission right where the shift linkage is connected to the transmission.

We do have a problem with that sensor commanding a downshift while driving at freeway speeds. I even had one shift the trans into 2nd gear while at 70 mph.

When you say you are at cruising speeds, how fast are you traveling. Speeds around 40 to 50 mph and the od will come in and out on a regular basis, depending on load. (throttle setting)

Customer: replied 9 years ago.
yes a cruising speeds of 55 the car will drop 200 rmps and then raise right back up

That is the tcc or the converter clutch coming out. 200 rpms is how much of an effect that the converter clutch has on rpm. Are there any trouble codes?

We do not have many problems with the solenoids for the tcc. but we do have problems with the converter clutch and with the valves in the valve body.

Customer: replied 9 years ago.
yes sorry, the trouble code is 1744

That DTC is for Excessive slip detected when tcc commanded at 100%

That is always a converter failure. You may get away with a trans flush, but I doubt it. Every time that I have that DTC, I end up replacing the converter.

Customer: replied 9 years ago.
so you are saying i should pull the tranny and put a new converter in
Yes, the converter clutch is either worn out or the seals inside the converter have failed. The converters are not easily rebuilt as they have to be cut apart and rewelded after the rebuild.
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