4l60e dropping out of overdrive

[bigdog379x]

My 4l60e recently started dropping out of overdrive randomly when warmed up. It will drive fine and stay in overdrive for a good 10 miles from a cold start, but then once it is warmed up it will jump out of overdrive and downshift. It will go shift back to overdrive but it will keep randomly dropping out of overdrive. Transmission shifts smooth in all gears even into overdrive. Anybody know what that could be?

 

[Hezsus]

is your brake light on?

 

[bigdog379x]

Idk, i would have to find out if it is or not, i dont think it is though? What could that mean?

 

[Hezsus]

overdrive is controlled with a switch that will disengage when you tap the break pedal or if you turn off/disconnect the abs module or if it had a fault. if its not something related to that its likley internal.

 

[SAATR]

overdrive is controlled with a switch that will disengage when you tap the break pedal or if you turn off/disconnect the abs module or if it had a fault. if its not something related to that its likley internal.

I think you may be thinking of torque converter lockup, which will disengage when you hit the brakes. Overdrive (and any other gear, for that matter) is dependent on speed, throttle position, and engine load. If the TPS is faulty it may be forcing the PCM to command a downshift by reading more throttle percentage than actually exists. The MAP sensor is also used to calculate load, and could cause an issue if reading incorrectly. I know that the CTS will also make the PCM hold gears longer to facilitate warmup when the engine is cold, but shouldn't cause a downshift. Others may have a better answer, but to my knowledge it could be those issues or an internal problem.

 

[NacIK]

I don't know about OD kicking in and out, but I know my TCC would lock and unlock frequently under part throttle. Mine was doing it because the transmission fluid was nasty and needed to be changed. Fifteen quarts and a filter later my transmission runs smooth as butter. My only complaint is that it is TOO smooth!

 

[Hezsus]

I think you may be thinking of torque converter lockup, which will disengage when you hit the brakes. Overdrive (and any other gear, for that matter) is dependent on speed, throttle position, and engine load. If the TPS is faulty it may be forcing the PCM to command a downshift by reading more throttle percentage than actually exists. The MAP sensor is also used to calculate load, and could cause an issue if reading incorrectly. I know that the CTS will also make the PCM hold gears longer to facilitate warmup when the engine is cold, but shouldn't cause a downshift. Others may have a better answer, but to my knowledge it could be those issues or an internal problem.

Yes i was thinking the TCC lockup, my bad.

 

[TruckinAin4Sissies]

TCC should only be a 200 RMP fluctuation (on or off).

To test Torque converter lockup:
*Get up to a steady speed (55+)
*Use throttle not cruise control
*Right foot- on accelerator (holding speed)
* Left Foot- Lightly press brake pedal

The RPM's should climb about 200 RPM's.
If they don't then lockup isn't working.

I've read about some fixes for this eg: Solenoid replacement or even a.pinched wire near the valve body (internally)



-Truckin'-