3-4 harsh shift 4l80e

[NickTransmissions]

@bucket @NickTransmissions

I forgot, I fixed this about a week ago but i figured out why I thought it as a 3-4, then realized it was 2-3

It wasnt the shifts, my TCC Lockup occurs at the same time as the shifts(according to scan tool)
Lightly holding the brake confirms the shifts are actually beautiful(since doing the TAPs reset)

I also finally nailed down the MAF as being bad, I couldnt get proof of it being irrational on my live data or on my freeze frames, but during some accels one day I got to see the value plunge during large throttle openings usually at speed , they would occur so fast and go back but I finally saw it.

So i replaced the MAF with a Delphi. Not an OEM part number Delphi, but a Aftermarket Delphi. Still cost a decent amount (100$) but it was locally in stock.

That made the shifts even softer. However, TCC lockup is still harsh and it has no pattern. It still slips a few RPM which is designed to , not an issue. But my next best guess would be my step dad used some cheap universal ATF last he did it. WHen I can ill do a DEX VI and filter and address the either leaky pan or gasket or whatever lol!

The part that got me about all this is that the TCC lockup occurs DURING 2nd gear and it doesnt wait a second after the shift before applying?

So the problem was a bad maf? If so, im not surprised. They cause all kinds of problems with transmissions when breaking bad.

Check the apply strategy tables to see when the TCC is supposed to be locking. Some have the tcc come on at WOT in 2nd to mitigate slip-driven heat build up but it shouldnt be locking up at part throttle, unless mods have been done...

 

[AuroraGirl]

So the problem was a bad maf? If so, im not surprised. They cause all kinds of problems with transmissions when breaking bad.

Check the apply strategy tables to see when the TCC is supposed to be locking. Some have the tcc come on at WOT in 2nd to mitigate slip-driven heat build up but it shouldnt be locking up at part throttle, unless mods have been done...

The strange part for me was the freeze frames were completely rational, i even checked my autel against my tech 2 to make sure the readouts were accurate.

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In order to obtain second gear, the PCM receives input signals from the transmission speed sensors (input and output), the Throttle Position (TP) Sensor, and from other engine sensors. These signals determine when to de-energize the 1-2 Shift Solenoid (SS) Valve.

Manual Valve: In the Overdrive range second gear, line pressure from the pressure regulator valve is directed as PRND4, PRND43, and Drive fluid pressures. The PRND4 fluid pressure is directed to the Automatic Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly and to the 2-3 shift valve. The PRND43 fluid is directed to the TFP manual valve position switch and to the manual 2-1 band servo. The Drive fluid is directed to the TFP manual valve position switch, the forward clutch, the 1-2 shift valve, and the accumulator valve.

Automatic Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly: Drive, PRND4, and PRND43 fluid pressures from the manual valve are directed to the DR, PRND4, and the PRND43 switches on the TFP manual valve position switch. This sends a signal to the PCM that the transmission is in Overdrive range.

1-2 Shift Solenoid (1-2 SS) Valve: When the 1-2 SS valve is de-energized, 1-2 signal fluid exhausts through the solenoid. A spring force holds the 1-2 shift valve to the extreme right.

2-3 Shift Solenoid (2-3 SS) Valve: When the 2-3 SS valve is de-energized, 2-3 signal fluid pressure forces the 2-3 shift valve to the extreme right against a spring force.

1-2 Shift Valve: Spring force holds the 1-2 shift valve to the extreme right. Drive fluid pressure from the manual valve changes into 2-3 drive fluid pressure at the 1-2 shift valve. This pressure is directed to the 2-3 shift valve, to the TCC PWM Solenoid Valve, and to the intermediate (second) clutch.

2-3 Shift Valve: Spring force holds the 2-3 shift valve to the extreme right. The 2-3 drive fluid pressure from the 1-2 shift valve changes into Front Band Apply (FBA) and is directed to the manual 2-1 band servo. The PRND4 fluid pressure from the manual valve is held at the 2-3 shift valve in order to be utilized in other gear ranges.

3-4 Shift Range: Spring force holds the 3-4 shift valve to the extreme right.

Forward Clutch: Drive fluid pressure from the manual valve applies the forward clutch.

Intermediate (Second) Clutch: Second fluid pressure from the 1-2 shift valve applies the intermediate clutch. The 2-3 drive fluid pressure from the 1-2 shift valve seats the # 4 checkball, causing the fluid to flow through two orifices and into the center support. This applies the Intermediate (Second) clutch. The 2-3 drive fluid pressure changes into Second apply fluid pressure at the orifices.

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iS the highlighted above relevant? And I dont think it will affect the TCC lockup, but I did see this:

Updating TAP information is a learning function of the PCM designed to maintain acceptable shift times. It is not recommended that TAP information be reset unless one of the following repairs has been made:
^ Transmission overhaul or replacement
^ Repair or replacement of an apply or release component, such as the clutch, band, piston, or servo
^ Repair or replacement of a component or assembly which directly affects line pressure

Resetting the TAP values, using a scan tool, will erase all learned values in all cells. As a result, the PCM will need to relearn TAP values. Transmission performance may be affected as new TAPs are learned. Learning can only take place when the PCM has determined that an acceptable shift has occurred. The PCM must also relearn TAP values if it is replaced.

Should I reset my TAPs again?

 

[AuroraGirl]

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