Why is my automatic transmission disengaging?

Question

This almost entirely happens when I first use car after being off for more than 8 hours. When decelerating to a stop my transmission instead of going to first gear is disengaging. Applying the gas simply revs the engine. To re-engage the transmission it is necessary to turn off the car and restart the engine. After this happens the car drives normally and decelerates and downshifts normally. Any ideas?

This almost entirely happens when I first use car after being off for more than 8 hours. When decelerating to a stop my transmission instead of going to first gear is disengaging. Applying the gas simply revs the engine. To re-engage the transmission it is necessary to turn off the car and restart the engine. After this happens the car drives normally and decelerates and downshifts normally. Any ideas?


Added details: 98 Dodge Stratus 2.5L V6 with 75k miles. Transmission fluid color and level both appear normal.

Answer 1

I had an 81 Escort years ago that used to do that, The engine vacuum system is used on mostly older cars to provide a engine load feedback signal to the tranny.If the car uses this system there will be a little flying saucer shaped thing with a hose on one side and a mechanical linkage on the other. these are sometimes called vacuum motors. kickdown actuators, or dashpots. you probably have a bad one.
Newer cars with electronic engine and transmission controls rely instead on the control module to calculate the engineload although some have a vacuum sensor of some sort. Most use calculations involving readings from the throttle position sensor, the airflow sensor and the transmission input speed sensor. It is possible to have a faulty sensor that will let teh engine run okay but cause the tranny to act up.
If you have a newer car have someone scan the computer error codes.
One other thing that can cause this on newer cars is a faulty alternator or battery . When you let off the gas to slowdown, the system voltage may be dropping enough to cause the transmission control unit to stop. When this happens , you have to turn the key off and back on to reset the tcu.

Answer 2

You don't mention the age of your vehicle, but it sounds to me like you have a faulty shift solenoid or a faulty vacuum line.

Turning the vehicle off, disengages the shift solenoid (of removes the vacuum) and resets it. The heat build up from trying to function allows it to operate thereafter.

Take your vehicle to a transmission shop and get it checked out.

Answer 3

go to Auto Zone for a free scanning.
let me know the codes.
I guess is, a bad output sensor.