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MegaShift™ 4L80E Wiring

This page provides information on how the 4L80E automatic transmission from General Motors operates with the MegaShift™ controller, as well as the TunerStudioMS settings needed to configure the controller.

The 4L80E is a 4-speed (with overdrive), electronically controlled transmission, with ratios:

4 (OD)0.750

There are 40 teeth for the VSS sensor, and 31 teeth for the input shaft speed sensor.

Build information for the GPIO board to use MShift™ with a 4L80E is here: build guide The 'bill of materials' is here: 4L80E bom

The 4L80E is controlled through 11 pins. These are:

Inputs to GPIO
LTemperature Sensor Signal
MTemperature Sensor GND
NPressure Switch A (aka. Pin A)
RPressure Switch B (aka. Pin B)
PPressure Switch C (aka. Pin C)
n/a2WD/4WD Input (ground for 4WD)
n/aVehicle Speed Sensor (VSS input & output) - has its own 2-pin connector

Outputs from GPIO
ASol A (1-2) Switched GNDOn/Off20-40 Ohms (0.75 Amps Max.)
BSol B (2-3) Switched GNDOn/Off20-40 Ohms (0.75 Amps Max.)
CPressure Control Solenoid HighPower (nominal +12V)Switched 12V from harness
DPressure Control Switched GNDPWM (293Hz early, 614Hz late)0 to 60% (3.5 - 4.6 Ohms at 20°C, 1.1 Amps Max.)
E+12 Volt PowerHigh (nominal +12V)Switched 12V from harness
STorque Converter Clutch Solenoid Switched GNDOn/Off20-40 Ohms Early / 10-15 Ohms Late (PWM) (1.5 Amps Max.)

The main difference between the 4L80E and the default 4L60e output pattern is the pattern for solB (output2) is 'inverted':

Gear 4L80E 4L60E
P/N off ON
R off ON
1 off ON
2 off ON
3 ON off
4 ON off

The wiring inside the 4L80E transmission looks like this:

The corresponding AMPseal connections for the control/sense functions are:

AMPseal Pin
Sol APE4VB323
Sol BPM2VB435
switchAAD0EGT4 (jumper)26
Input VSSPT5VR314
Output VSSPT0VR12
Temp SensorAD2GPI330
Brake SenseAD7GPI43
Speedo OutputPT4PWM131
line pressure sensorAD4EGT227
2WD/4WD switchPE1GPI15
Spare Output1 (Clutch)PT7VB1 (jumper)11
Spare Output2 (Clutch)PA0VB212
Paddle UPPT6VR215

In addition there are:

AMPseal Pin
Power In (+12V)1
Power Grounds18, 19, 20
Vref (+5V)28
Sensor Ground17, Temperature/VSS/pressure sensor ground

On the GPIO, the connections are:

On MS-II™, MS-III controllers, the CAN paths are:

The CAN termination resistors are already in place on the MS-II™ and GPIO.

To wire the 4L80E transmission to the GPIO board, you need to make a number of connections:

You need a minimum 4.7 Ohm (or higher resistance - up to ~10 Ohms), 10 Watt (or more) resistor (such as Digi-Key 4.7CWBK-ND, $1.67) on the pressure control solenoid wire from the trans connector pin D to the GPIO board's pin 33. This resistor dissipates up to 4 Watts of power at low line pressures (maximum PWM percentages). As a result, the resistor can get hot, so mount it on a heat sink (ideally a metal block) in an area with plenty of air circulation. In conjunction with that resistor, you will need a 1N4001 diode placed between pin C and D on the 4L60E connector (the closer to the transmission connector the better). These two additional components cut the flyback spikes from the solenoid to manageable levels preventing damage to various GPIO board components and potentially cleaning up external signals such as the VSS.

If you want a 'mode selection switch' to force auto mode or enable manual mode, you can do this with a switch and two diodes (1N4001 or equivalent):

(This circuit only works with 'Shift Button Polarity' = "active low".)

When the mode switch is closed, auto mode will be used, regardless of what you do with the shift buttons. If the mode switch is open, pushing either the upshift button or downshift button will put you in manual mode (and pushing both OR switching the mode select switch to auto will put you back in auto mode).

The four resistors for the LEDs can be 330 to 390 Ohms, 1/4 Watt.

If you are looking for a 4L80E harness connector, try a scrap yard, or here:


The 4L80E uses three types of sensors:

  1. There is an early and a late model of the 4L80E transmission. The difference is the pressure control solenoid (aka. "force motor") changed from 293Hz to 614Hz (at the beginning of the 1994 model year), and there was no no dither requirement (and the case connector may have changed).
  2. VSS (output vehicle speed sensor) on 2WD vehicles is in transmission housing, on 4WD vehicles the VSS is in transfer-case.
  3. The ECU also senses a brake switch and turns off the TCC solenoid whenever brakes are applied.
  4. TCC lock-up solenoid is normally only energized in 4th gear, if the transmission temperature is above 250°F it will energize it in 2nd and 3rd as well. Early model TCC was on/off; late model is PWM but can be used as on/off under 500hp
  5. Duty cycle on the Pressure Control solenoid is inversely proportional to the throttle angle (as throttle angle increases, duty is decreased) At idle (minimum throttle), the duty is at max (60%). At WOT (wide open throttle), the duty is at min (0% or off). Note that the PC solenoid takes the place of the Throttle Valve cable on earlier transmissions. In the TunerStudioMS interface, the 0-60% signal has been converted to a 40-100% signal, where 100% means maximum line pressure, and 40% means minimum line pressure. This *should* be more intuitive for the user, hopefully.
  6. All solenoids share common 12V line on pin E (except Pressure Control solenoid, which has its own +12 Volt supply on pin C) and are switched on and off with ground.

Shift PatternSol A (1-2)Sol B (2-3)TCC Sol (LU)Pressure Control solenoid SolRatio
ReverseONOFFN/AON *2.077
1stONOFFON/OFF**ON *2.482
2ndOFFOFFON/OFF**ON *1.482
3rdOFFONON/OFF**ON *1.000
4thONONON/OFF**ON *0.750



Solenoid A20 - 4043.0
Solenoid B20 - 4043.0
TCC20 - 40 E / 10-15 L56.9 / -
Pressure Control3.5 - 4.58.1

Pressure Switch Manifold

The pressure switch manifold (PSM) is a multiple switch assembly consisting of 5 normally open (NO) pressure switches.

Fluid from various hydraulic control circuits is fed to this the pressure switch manifold which allows the ECU to determine which gear the shift lever is currently shifted into (not necessarily the actual gear the transmission is in). The switch contacts are normally open and close when fluid pressure causes them to. Depending upon the circuit, the switch may provide a ground path when closed. The table below shows a pin that is grounded by the PSM as a "0", while an open circuit shows a 12 (volts).

GearPin NPin RPin P
3rd (Drive)HIGHHIGHlow
4th (Overdrive)HIGHlowlow

Case Connector

ASol A (1-2) Switched GND
BSol B (2-3) Switched GND
CPressure Control Solenoid +12V
DPressure Control Solenoid Switched GND
E+12 Power
LTemperature Sensor Signal
MTemperature Sensor GND
NPressure Switch A
RPressure Switch B
PPressure Switch C
STCC Solenoid Switched GND

Main Line Pressure Tap

MegaShift has a line pressure sensing/logging function built it. It is digikey MSP6907-ND for $114. It's a 0.5-4.5 Volt output (accuracy ±5 psi), and has just a three wire hookup:

  1. 5V from Vref on Ampseal pin #28,
  2. ground, and
  3. signal to Ampseal pin #27.

It has a 1/8 NPT fitting - the same as the transmission port. However, a 90° elbow, or maybe even some tubing, will be required in most installs to keep the sensor away from the transmission tunnel.

4L80E Temperature Sensor Output

The 4L80E temperature sender can use the default sensor curve built in to the MShift™ code [with the default bias resistor (2.49K Ohms)]:

°C°F R (Ohms)
-40-40 100544
-28 -21 52426
-16 -10 18580
-4 23 12300
0 32 9379
7 40 7270
19 68 3520
31 86 2232
43 110 1200
55 131 858
67 145 675
79 176 333
91 194 241
103 213 154
115 239 115
127 260 79
139 284 60
151 302 47

TunerStudioMS Settings:

Most of the default settings for the 4L60E in the MShift™ code apply to the 4L80E as well. However, there are a few differences:

  1. The 4L80E has the same input pattern as the 4L60E (the defaults in the code). For the shift solenoid outputs, the only thing that you will need to change is Input 2 (SOL B) for the output, as it has the opposite pattern to the 4L60E: Shift Input Patterns

    Gear 4L80E 4L60E
    P/N off ON
    R off ON
    1 off ON
    2 off ON
    3 ON off
    4 ON off

  2. The 4L80E has an input shaft speed sensor with 31 teeth. Set 'Pulses/Revolution' = 31.

  3. The early 4L80E pressure control solenoid is PWM at 293 Hertz (same as the 4L60E). Later models apparently use 614 Hertz. If you are using a later model 4L80E (apparently at the beginning of the 1994 model year) change the 'PC PWM Period' to 1.629 milliseconds.

  4. If you have the earlier transmission (1993 or before), you can enable the 'dither' cleaning pulse under 'PWM Refresh and Dithering'. The values are: If you have a 1994+ 4L80E transmission, the dither cleaning pulse was not used on these (disable dithering by entering 0 for the PC dither duration).

  5. The 4L80E does not use a lock-up feel solenoid, it PWMs the TCC solenoid directly. If you wish to pulse width modulate your torque converter's clutch, you will need to select 'Use PT3/Amp32 for LUF and SPR2/PA0/VB2 for TCC' under 'Spare Ports/Clutch Outputs', then set the PWM values under 'Lock-Up Feel Parameters'. Then you would use Amp pin 32 for PWM'd TCC control. Spare port 2 will then be on/off with the TCC, and unavailable for other uses (except for TCC 'applied' indicator light control, if you want that).

    You can use the on/off output for TCC control if you prefer, of course, though the TCC engagement might be a bit harsh.

  6. The gear ratios are different:

    Gear4L80E Ratio
    4 (OD)0.750

This is how these settings should look in TunerStudioMS:

Use the same patterns for Park and Neutral.

The settings image above was contributed by Guillaume Scheidt, who is forum user 'gui67'. Please verify it before using. Many thanks to Guillaume for permitting us to display it here.

Here is a draft MSQ (for 2.007 code) for the 4L80E with the changes mentioned above (including the PWM TCC):

Right click and 'Save As'

The values in this MSQ are for an early 4L80E with a 293 Hz pressure control solenoid and dithering. Check all settings carefully to be sure they are right for your transmission.

Last Updated: 03/31/2010 09:47:18
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© 2010 Dave Hjort and Lance Gardiner. All rights reserved. MegaSquirt©, MicroSquirt©, and MShift™ are registered trademarks. This document is solely for the support of MegaSquirt® boards from Bowling and Grippo.