Can someone describe for me the sequence of events during the time that the automatic transmission is changing gear. Specifically when I drive a manual and change gear I take my foot of the throttle while changing. How is the power controlled on an automatic? Does it keep the injectors closed or does it cut the spark.
George

 

Torque Converter.

Any ways, I only know the basics when it comes to automatics, so here's a nice video that explains it simply.

 

The torque converter transfers power from the engine to the transmission. This takes a finite amount of time, up to one or two seconds on most cars. I would imagine that during this time the power has no where to go, so needs to be removed. If this is so, then how is my question. Is it via the ignition or the fuel injectors?
George

 

It takes much less time for the TC to engage. I'd say one second would be the maximum time. But like the video mentioned, the TC is fluid coupling. Say you came to a red light. In a stick, you'd depress the clutch and brake to bring the car to a stop. In an automatic you just depress the brake. When you come to a complete stop, the fluid inside the transmission is spinning at a very, very slow pace allowing you to keep the car in one spot with light brake pressure. Now, say you kept your foot on the brake and give the car some throttle. The more throttle you give the car, the more pressure you need to give the brake pedal to keep the car still. This is because as you increase the engine speed, more fluid enters the TC and starts to spin more rapidly which starts sending the power through the tranny and to the wheels.

Unlike a clutch, where the transmission can be completely disengaged from the engine, the TC in a automatic can not be completely disengaged. If the engine is spinning, the TC is spinning. However, a TC can of a lock up type in which both sides the of the TC lock together to spin at the same speed with no slippage, allowing less heat in the transmission and better MPG.

There is much more that can be discussed about the TC such as stall speed and diameter that I won't get into.

As for your question, no the ignition is always firing while the engine is on as well as the fuel injectors.

 

I'm more interested in the situation where I've left the lights with my foot to the floor. I notice during the brief time that the transmission is changing gear that there is no rpm surge that I might expect if the engine was still developing full power. The Stock PCM tables show a TCC shift delay of 2 seconds and a target shift time of about 0.8 seconds. What I want to know is what happens during this time to stop the engine from revving up when it's not applying torque to the rear axle. If I've got this completely AOT let me know.
regards,
George

 

An automatic trans is always applying torque to the rear. If not, you would have a slipping (bad) transmission. I think you're having a hard time grasping the concept because you're trying to equate the operation of an automatic to that of a manual. A manual trans is either "in" or "out" of gear, and it grabs instantly as soon as the clutch is snapped out. The shift delay you're referring to is the time it takes the automatic to go from one gear to completely into the next. Automatics don't grab the gears with a bang-bang-bang shift like you can shift with a manual, unless you have the trans built that way. For lack of a better term, an automatic glides into the gears, but it doesn't slip between the gears, which is why you don't see an rpm surge.

 

Thanks for your patience and the info.
regards,
George