4t40 transmission

[Lynn5907]

Seems like a great trans so far. Now I was looking into the parts that go into it. What the neck is a coast clutch ( besides the obvious) what does it do. For example I put car into 3rd gear at 45 non and noticed the rpms where not steady like I thought it should be. Like it would very + or - 800 rpms according to gas input .... If I smashed it of course it would shift to second gear. 

 

What is direct clutch? Does it just make a mechanical connection instead of power through fluid coupling? 

[Lynn5907]

On 10/19/2018 at 3:59 PM, Frosty said:

 

 

[Lynn5907]

So come to find out it is cuz the temp gauge reads cold. As soon as it hits 150 and above it shifts fine. Anyone think different?

[TWO LANE BLACK TOP]

Do you still have the thermostat out of it...?? Actually it is important for it to be in place....It key to help get the car up to and maintain proper operating temp.....So the fuel system can go from open loop to closed loop along with all the other related things...(timing injector pulse width trans shift points when the cooling fans come on ETC..) When it is in the open loop condition that means that all the sensors are not talking to each other and is basically running on the factory cold start perameters....(rich condition) all the time..when then check light is on that also sends it into a rich condition..Will also have an adverse effect on gas mileage among other things....

Pretty much what happens when you turn the key on is..

The fuel pump turns on then the butterfly or choke plate or whatever we are calling today....In the idle air control valve...Sets or closes which  works like the choke during startup.....when the engine starts and is running... It is in open loop....As the engine warms up to operating temp..The coolant temperature sensor tells the PCM (power control module)... Then the MAF (mass airflow sensor) and the oxygen sensors start talking to each other...then the system is in closed loop then all the related sensors IAT (inlet air temp) idle air control.. The trans sensors...ETC..Are constantly changing the timing...injector pulse width...transmission shift points...According to air temp..humidity...and throttle position.....The thermostat is key to help in making all that happen correctly at the proper time...This is a very basic overview and by NO means a complete or in depth explanation......

Also when the check engine light is on that also puts it into open loop condition (running rich)....takes a few minutes to get the trans fluid warm too....

Edited October 23, 2018 by TWO LANE BLACK TOP

[Frosty]

On 10/20/2018 at 2:51 AM, Lynn5907 said:

What the neck is a coast clutch ( besides the obvious) what does it do.

What is direct clutch? Does it just make a mechanical connection instead of power through fluid coupling? 

A coastal clutch is used for forward engine braking. This allows the transmission to help slow down the the vehicle and apply load to the engine to help slow it down.

By definition, an automatic transmission is fluid coupling. These is no direct connection to the motor and the output shaft of the transmission.  

[Lynn5907]

I think the only time a auto is mechinal is when the converter locks up? No? That make since so engine brake. Ill pay att and see if it does that

[Frosty]

It is still technically fluid coupling since the transmission fluid separates the flywheel from the rest of the transmission inside the torque converter. Even in a lock up situation, the inner and outer stators are moving at the same speed (1:1), they are not physically or mechanically connected or locked together. They are just rotating at the same speed relative to each other.

Edited October 24, 2018 by Frosty

[Frosty]

On 10/22/2018 at 9:08 PM, Lynn5907 said:

So come to find out it is cuz the temp gauge reads cold. As soon as it hits 150 and above it shifts fine. Anyone think different?

 

On 10/22/2018 at 10:20 PM, TWO LANE BLACK TOP said:

Do you still have the thermostat out of it...?? Actually it is important for it to be in place....It key to help get the car up to and maintain proper operating temp.....So the fuel system can go from open loop to closed loop along with all the other related things...(timing injector pulse width trans shift points when the cooling fans come on ETC..) When it is in the open loop condition that means that all the sensors are not talking to each other and is basically running on the factory cold start parameters....(rich condition) all the time..when then check light is on that also sends it into a rich condition..Will also have an adverse effect on gas mileage among other things....

Pretty much what happens when you turn the key on is..

The fuel pump turns on then the butterfly or choke plate or whatever we are calling today....In the idle air control valve...Sets or closes which  works like the choke during startup.....when the engine starts and is running... It is in open loop....As the engine warms up to operating temp..The coolant temperature sensor tells the PCM (power control module)... Then the MAF (mass airflow sensor) and the oxygen sensors start talking to each other...then the system is in closed loop then all the related sensors IAT (inlet air temp) idle air control.. The trans sensors...ETC..Are constantly changing the timing...injector pulse width...transmission shift points...According to air temp..humidity...and throttle position.....The thermostat is key to help in making all that happen correctly at the proper time...This is a very basic overview and by NO means a complete or in depth explanation......

Also when the check engine light is on that also puts it into open loop condition (running rich)....takes a few minutes to get the trans fluid warm too....

Two Lane's explanation is spot on. The differences between open and closed loop performance and operation are mind boggling. Your car is not designed to operate at cold (internal engine) temperatures for very long. Let's face it, cold te,mp / open loop is intended to operate for only the first few minutes beginning with start-up.  The engine is not designed to operate there for \very long.

Edited October 25, 2018 by Frosty

[Lynn5907]

Thanks again you all. I like to know all this stuff in-depth. I've replaced timing chain and belts before, but like to know why all this is necessary so to speak. The check engine light is p0420 code. It cuz the upstream 02 is bad. I should be able to clean the cat and have done it before... Didn't know the thermostat was so important and would make it run open loop however it does all make since. Honestly didn't even think about it until l the weather got cold and shifts where funny in fact it maybe part of the reason behind p0420 as well as the open loop 02 sensor. Feel like I got lucky when it came to this car. Seems like at one point someone had taken care of the car as due to all the maintenance paperwork I found in the trunk. I basically got the car ($400) from a dude that thought he could fix it but was over his head. The day I got it, it was covered in oil due to bad oil pressure switch and melted + wire from alt that grounded to motor. Simple stuff really but all together it didn't run, then when it did only off of two cylinders thanks to a burnt coil pack that read 35k cly1 5k cyl2 40k cyl3 8k cyl4 ohms new pack read like 10k. Found some random wires melted together as well. O and the key stopped working the next day (that was fun) I'm sorry to say I kicked the car that day 😫 ... Wound out taking out ign switch and beating out cyl sleeve of course the transistor came out witch set off security light. Found a resistor from a old radio security lights been off for months now bad thing can use anything to start car. 

"""""Btw I used duck tape ( black so no one notices ) to keep it warm for now until l can afford to get it correct. """"                         

 

Edited October 25, 2018 by Lynn5907