Transmission o/d light flashes and does not shift properly

This is an electronically controlled transmission. No vacuum hose. It doesn't have a modulator valve. The shifting is done by shift solenoids.

speed sensor failure

Symptoms of a P0500 DTC may include
: loss of anti-lock brakes the "anti-lock" or "brake" warning lamps on the dash may be lit the speedometer or odometer may not work properly (or at all) your vehicle's RPM limiter may be decreased the shifting of an automatic transmission may become erratic other symptoms may also be present

Read more at: https://www.obd-codes.com/p0500
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Sounds like a coil breaking down. Try this for a test, get going to around 45 mph and lightly accelerate, is the is miss is reproduced then the most likely cause is the secondary ignition system. I.E plugs or wires or a coil.

Which seal was replaced? The torque converter (or main seal). Or one of the axle seals? Or another seal somewhere else? Usually the O/D light flashes when you have a TCC solenoid or shift solenoid problem. Like... if there's no power going to the torque converter lock-up solenoid, It will not go into fourth gear because the tcc solenoid cannot lock up the torque converter properly. Depending on which seal you've replaced, it may just be a coincidence. Maybe the light would have done this regardless. Either that or maybe something is not connected tightly. Maybe one of the transmission connectors.
I had the same light flashing in mine when I disconnected the valve body wiring connector because my torque converter was locked up solid and that was the only way I could move the car into the garage.
I would take a good look at the transmission connectors and make sure that all the connectors are tight.
I hope this helps, good luck!

daytime light relay stuck on..replace relay..

take it to the dealer and have a cert Ford / Merc shop program the comp, they can reboot and install what your car calls for ,

DTC P0715 CHRYSLER - Input Speed Sensor 1 Circuit
P0715 is detected when TCM or ECM does not receive the proper signal from the sensor.

The input speed sensor detects the primary pulley revolution speed and sends a signal to the Transmission Control Module (TCM) and Engine Control Module (ECM).

Symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Possible shifting problems

Possible causes
- Transmission speed sensor circuit is open or shorted.
- Poor transmission speed sensor circuit connection
- Faulty transmission speed sensor

Hope this clues helps to solve it.

It is inside the the side pan of the transmission,ss1 ss2 ss3 are identical.SS1 is the top solenoid.You will need to remove the subframe to get the side pan off, and this is tricky.Good luck!

yes, it's the speed sensor. It is mounted in the transmission above the axle as seen in picture below. The part is $24 at autozone.com. Before buying the part, make sure the connector is properly attached to the sensor and the wiring is intact. If the wiring is good, the sensor is most likely the problem. let me know if you have any more questions.

Check the transmission fluid first. it sounds like one of the clutch plates is sticking.

If you shift into second after you've stopped, can you get the car moving?