2012 CTS-V 6l90 TCC pressure dump after apply?

[TransGo Robert]

Hey Rob,

Just with respect to the TCC circuit I've always thought it was:

pump => line_pressure => line_pressure_reg_valve_PCS1 => converter_feed => converter_reg_valve_PCS_TCC => converter.

Can you please let me know where I'm going wrong?

You are looking at the hydraulics when it is not locked, it all changes when the flow is reverse in lock up.

In lock-up, it goes like this:

The pump creates a vacuum drawing fluid into its inlet, and then displaces it to its outlet.

Next the pressure regulator valves restrict the flow up to the force if the spring required to move the valve into its regulating position generating and regulating line pressure.

Once the PR has built the desired line pressure, the extra pump volume goes into the converter charge (goes to the cooler in lock-up, by-passing the converter completely) until the desired pressure is reached (limited by the converter limit valve) and then it opens and dumps the rest on the slide reducing circuit reducing the pump volume output.

Both the line pressure solenoid and the TCC solenoid are fed AFL pressure. The actuator Feed Limit valve gets line pressure and pass it to the solenoids until it gets to110 psi. Once that is reached, it dumps the rest of the pump output volume to dump to ensure the pressure never goes above 110 psi to the solenoids.

The line pressure solenoid then outputs a certain % of its provided AFL feed based on the computer command to the boost valve which adds to the PR spring force raising line pressure.

The TCC solenoid output a % of its AFL feed as commanded by the computer to the TCC control valve and the TCC regulator valve.

Once the TCC solenoid output pressure is high enough to overcome the spring force of the TCC control valve, it strokes against its spring and reverse the flow in the converter.

Finally when the TCC solenoid output pressure is high enough to overcome the spring force if the TCC regulator valve, it sends fluid pressure into the 8apply path to apply the clutch in the converter.

Screenshot_20231219_172656_Acrobat for Samsung.jpg

[hjtrbo]

And today I learnt I don't like hydraulics. I'll stick to being a sparky. It's either on or off on my world.

[TransGo Robert]

And today I learnt I don't like hydraulics. I'll stick to being a sparky. It's either on or off on my world.

LOL. The Beauty of it is that electricity and hydraulics are identical. Both are fluids, one made of electrons the other one of ATF. Pressure = Voltage, flow in GPM is the = current in AMP, and resistance to flow is the same for both.

[hjtrbo]

LOL. The Beauty of it is that electricity and hydraulics are identical. Both are fluids, one made of electrons the other one of ATF. Pressure = Voltage, flow in GPM is the = current in AMP, and resistance to flow is the same for both.

Cheers Rob. Sounds very familiar. The logic of hydraulics however, in particular spool valves / pump slides requires some extra thought from my side.

[hjtrbo]

Hey ya Rob, I want to 'chew the fat' so to speak with you again if you don't mind? The reason I'm coming back to this is I want to verify if my tuning method of allowing the tcc pcs pressure to spend the rest of it's days at 758kPa is valid. The TCC if locked, is unlocked for all shifts then re-locked if scheduled.

This discussion is with respect to an OEM 6L90 fitted with an OEM 6 bolt ZL1 converter. Feel free to pm me if you want.

You got me right back into the books, damn you lol.

My terminology is not good, forgive me; I want to make a statement with respect to steady state operation:

TCC Apply Pressure = (or is very close to) Line Pressure (up to the convertor feed limit pressure value)

Can I say that?

[TransGo Robert]

Hey ya Rob, I want to 'chew the fat' so to speak with you again if you don't mind? The reason I'm coming back to this is I want to verify if my tuning method of allowing the tcc pcs pressure to spend the rest of it's days at 758kPa is valid. The TCC if locked, is unlocked for all shifts then re-locked if scheduled.

This discussion is with respect to an OEM 6L90 fitted with an OEM 6 bolt ZL1 converter. Feel free to pm me if you want.

You got me right back into the books, damn you lol.

My terminology is not good, forgive me; I want to make a statement with respect to steady state operation:

TCC Apply Pressure = (or is very close to) Line Pressure (up to the convertor feed limit pressure value)

Can I say that?

110 psi all the time is going to be very hard on that little flimsy lock-up piston! That yields 124 psi at the clutch in a stock application. There is no need to ever go above 80 psi on that piston, it just distort the heck out of it and makes it less able to hold, not more. Not to mention the issue with the stock back cover that is so prone to warping. If you have a converter with billet cover and billet piston then it is not going to hurt anything, but otherwise I strongly advise against doing that.

As for this "TCC Apply Pressure = (or is very close to) Line Pressure (up to the convertor feed limit pressure value)", the converter feed limit pressure valve is only when not in lock-up. It is easy to confuse converter valve with converter clutch valve. Once in lock-up that converter feed limit valve now controls only the cooler pressure, it no longer has anything to do with converter pressure. The TCC regulator valve is the one that is 100% in charge of controlling the pressure fed to the converter when the lock-up is applied.

[hjtrbo]

110 psi all the time is going to be very hard on that little flimsy lock-up piston! That yields 124 psi at the clutch in a stock application.

We love data, screenshot below with commanded tcc pcs at 758kPa and pcs1 commanded at 110kPa generating a calculated line pressure approximately of 557kPa (80psi). In this case the converter clutch sees that same pressure (80psi)?

it just distort the heck out of it and makes it less able to hold, not more. Not to mention the issue with the stock back cover that is so prone to warping.

I have seen many of Precision Transmission's tear downs with 3 bolt 6L80 converter faults. Is that why GM went to a 6 bolt converter for higher torque applications?

If you have a converter with billet cover and billet piston then it is not going to hurt anything

The dream.

The TCC regulator valve is the one that is 100% in charge of controlling the pressure fed to the converter when the lock-up is applied.

I see that now. Thanks.

[TransGo Robert]

We love data, screenshot below with commanded tcc pcs at 758kPa and pcs1 commanded at 110kPa generating a calculated line pressure approximately of 557kPa (80psi). In this case the converter clutch sees that same pressure (80psi)?



I have seen many of Precision Transmission's tear downs with 3 bolt 6L80 converter faults. Is that why GM went to a 6 bolt converter for higher torque applications?.

That is a funny way to command things with the tune you have, normally it would never command the solenoid to try and output higher then calculated line pressure, since it that is physically impossible. But in your case, under those conditions, yes of course the lock-up apply pressure would be limited to 80 psi.

The 6 pads vs 3 pads is not related to lock-up, it just something that is needed in higher torque applications to prevent breaking the flexplate, distorting the back cover or breaking bolts. The lock-up piston that gets distorted when too much pressure is applied to it is inside and flexes towards the cover sincere there is no longer any pressure between it and the back cover so it just bows and end up looking like a bowl of soup.

[hjtrbo]

4L60 lockup solenoid style. With the smooth ramped apply. Keeps things simple in the tune. I let line pressure do the work. People with jacked up torque values will have issues.

[noobers8]

Just a little update ?. After running it with the offset/gain setup for a little while I have decided to revert back to a desired TCC pressure table. Ultimately I could not find a happy medium on lockup pressure that would hold under load but not apply too hard and drop rpm enough to unlock in 5th /6th while under light loads up hills ?. I could have raised the 5th/6th lock up schedule but I was not willing to give up that ability due to fighting trans temps as it is. For what ever reason I still can?t get the adapts to work in my favor and ended up disabling them as well.

[hjtrbo]

The adapts are still a mystery.

[hjtrbo]

What sort of trans temps are you fighting? The are lots of temperature adder / modifier tables behind the scenes

[noobers8]

Seems like keeping it under 180 is nearly impossible while not on the highway ?. I try to lock the tcc @ 45 mph to try and combat this while cruising in the city.

[hjtrbo]

180 is ok. 210 would be concerning.

You still running the factory cooler circuit? Can always check cooler is clean. And if you're in a hot location that plays in too

[noobers8]

Had many conversations with David over at circle d and he preaches over 180 is detrimental to the clutch packs. I?m running the factory radiator trans cooler and a tru cool 40k

[hjtrbo]

That's only just into the normal engine coolant temp region. I'm not going to argue with him, but surely there's some allowance around that number. What's your typical ambient temp this time of year?

[noobers8]

We are talking trans temp here and not engine correct ? And Ambiant is around 30-49 deg Fahrenheit

[noobers8]

Where is the tcc regulator valve located ? I?ve this this issue rear its ugly head once again?..due to the randomness, I?m leaning toward a hardware issue at this point.

[TransGo Robert]

Where is the tcc regulator valve located ? I?ve this this issue rear its ugly head once again?..due to the randomness, I?m leaning toward a hardware issue at this point.

In the valve body.

[noobers8]

It is odd that it happens around the same mph every time though ? light throttle usually. Shifts to 5th tcc locks and I have 6th scheduled to shift at 60mph but it doesn?t until 65 but 60 mph is when the tcc goes from 65psi to 16 psi back up to 58 psi every time? The randomness is what is throwing me off?.. and I do have lock while shift enabled.