4L60E Shift Pressure Knowledge

[PHLTHS]

Hi All,

I just would like some clarification about the 4L60E experts here on the forum.

From what I can tell, the pump in the auto picks up the fluid and pumps it towards the PRESSURE REG VALVE / BOOST VALVE located in the pump assembly itself.

This is LINE PRESSURE that is coming from the pump, when in drive ranges from Min: 55-65psi to Max:170-190psi from factory. How pressure is blead off is determined by the "TORQUE SIGNAL" as I think the clutch packs do not require this full force?

This "TORQUE SIGNAL" is recieved from the EPC / PCS (PRESSURE CONTROL SOLENOID VALVE). This is a table that is applying a current in mA which alters the PRESSURE REG VALVE / BOOST VALVE bleed off point. This can be alterated / scaled using the Force Motor Current table D3801 to either increase / decrease the overall pressure for the entire system including TCC's fluid pressure. I've also seen some people turn the screw at the back of the EPC / PCS Valve either 1/8 to 1/4 of a turn clockwise to change the base setpoint.

When using the MAF a per normal on the LS1's there Torque Signal Pressure is scaled correctly. It ranges from 0-96PSI Torque Signal Pressure. Just like with E38's when running SD if the airflow table isn't corrected so that the correct Delivered Engine Torque is correct the Auto might not apply the correct line pressure as required.

I guess then the only question I have about the Auto's is this:

D3801 Force Motor Current controls the overall pressure for the transmission.

D0701 Base Pressure 1>2 Shift
D0702 Base Pressure 2>3 Shift
D0703 Base Pressure 3>4 Shift

So, are tables are basically altering the pressure applied for the actual shift itself just to complete the shift? So more pressure = firmer shift / less pressure = softer shift.

But once applied, the claming force to keep the clutch packs locked up is based on D3801 bascially? or is it based on either of the D0701 - D0703 tables to determe each gears clamping force?

I'm in the middle of building a 4L60E using the Sonnax HP-4L60E-01 Performance Shift Pack and I'm worried that not having this tuned correctly will allow the clutch packs to slip with boosted power etc.


Thank you.

[joecar]

The TCM commands line pressure by sending a PWM signal to the PCS solenoid (PCS regulates Torque Signal pressure which pushes Boost Valve which (thru spring) pushes Pressure Regulator valve which regulates Line pressure).

Table D3801 maps desired pressure @ current temperature to current to the PCS (current being controlled by using PWM).
D3801 should be made to match the PCS solenoid's ability... D3801 determines the mapping from desired pressure to PCS current mA.
If you move D3801 down you can increase line pressure, but your are faking out the TCM (it thinks it commanded mid pressure, but D3801/PCS delivered high pressure, TCM thinks it was too harsh so it sets the shift learning to softer).


Base line pressure is determined by calculation using current cylinder airmass and other things)...
MAF and VE tables must be accurate otherwise base line pressure will be wrong (too low = slippage)


Tables D0701-3 set the pressure during each shift (and after the shift the pressure is reduced back since the clamping requires less pressure than applying (spinning up component)).
You can soften the shift and keep the pressure firm by adding torque reduction in tables D0801-3.

[joecar]

After your trans build, you have to monitor line pressure at the line tap on driver side of the case.