I have a '86 GMC dually 1ton 4x4, that I would love to have a 4L80E in, in place of the th400. I know I can get a trans computer from Jet and others in the aftermarket, but they're pretty pricey. I've seen bits and pieces online of people talking about using the trans computer out of late model diesel trucks, but nothing definitive. Can anyone on the list point me to some solid info on the use of this computer? Thanks.

just my opinion here , so please take it as that...


Diesel computer is old tech to control the 4L80E.

Get the Comp U shift. We have used them in several applications..... 4L60E , 4L80E , AODE. Very programable.

The Tech guys at Comp U shift have helped us with stuff. There are also some back doors into the programming to even more stuff with the Comp U shift.

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If you can't fix it with a hammer, you have an electrical problem.

The Compushift is the route I'm going as well. Thought about a TCI....no technical support whatsoever unless you call FAST and bother them.
The thing on the compushift is that you MUST buy the little display with the 4 square buttons on it to do the back door programming. You can even set it up to do lockups based on percentage of throttle all the way up to WOT, but you must have the programmer.

If you really want to go the diesel route, look here:
www.tunercat.com
$D3 16128420 92 - 93 C/K Diesel Truck L65, Auto Trans, TCM
I sent them a bin that I pulled out of a diesel trans contoller's prom and they had it broken down in like 4 hours.
Here's a list of everything that was in the bin:
ECM Switch Parameters
Output Speed Low Diag. (Error 24)
Trans Press Switch Diag. (Error 28)
Brake On Diag. (Error 37)
Brake Off Diag. (Error 38)
System Voltage High Diag. (Error 53)
Trans Temp High Diag. (Error 58)
Overdrive Diag. (Error 68)
TCC On Diag. (Error 69)
Engine Speed Low Diag. (Error 71)
Output Speed Loss Diag. (Error 72)
Trans Temp Low Diag. (Error 59)
Force Motor Current Diag. (Error 73)
Input Speed Sensor Diag. (Error 74)
System Voltage Low Diag. (Error 75)
Transmission Hot Diag. (Error 79)
Quad Driver 1 Shift B Diag. (Error 81)
Quad Driver 1 Shift A Diag. (Error 82)
Quad Driver 1 Diag. (Error 83)
Undefined Ratio Diag (Error 85)
Low Ratio Diag. (Error 86)
High Ratio Diag. (Error 87)
Manual Mode Enable (X = Disabled)
Downshift Turns Off TCC (X = Yes)
Rapid TPS Decr. Turns Off TCC (X = Yes)
Very Low TPS Turns Off TCC (X = Yes)
Hot Trans.Turns Off TCC (X = Yes)
Cold Trans.Turns Off TCC (X = Yes)
Cold EngineTurns Off TCC (X = Yes)
Gradual TCC Release (X = Enabled)
ECM Constants
Mechanical 1st Gear Ratio
Mechanical 2nd Gear Ratio
Mechanical 3rd Gear Ratio
Kickdown Mode Enable %TPS Threshold
Kickdown Mode Disable %TPS Threshold
Low PRNDL Upshift Speed Threshold
Low PRNDL Downshift Speed Threshold
Drive2 PRNDL Upshift Speed Threshold
Drive2 PRNDL Downshift Speed Threshold
Manual Mode 2->3 Shift Speed Threshold
Manual Mode 3->2 Shift Speed Threshold
Manual Mode 3->4 Shift Speed Threshold
Manual Mode 4->3 Shift Speed Threshold
Pressure Reduction for 1->3 Upshift
1->3 Upshift Pressure Reduction Time
Pressure Reduction for 1->4 Upshift
1->4 Upshift Pressure Reduction Time
Pressure Reduction for 2->4 Upshift
2->4 Upshift Pressure Reduction Time
Garage/Normal Shift Speed Thresh (P/N)
Garage/Normal Shift Speed Thresh (Drive)
Garage/Normal Shift Press Delta (P/N)
Garage/Normal Shift Press Delta (Drive)
Garage/Normal Shift Press Delta (Rev)
Lower Adaptive Learn Trans Temp Thresh.
Upper Adaptive Learn Trans Temp. Thresh.
Adaptive Learn Modifier Lower Limit
Adaptive Learn Modifier Upper Limit
Hot Transmission Enable Temp. Threshold
Hot Transmission Disable Temp. Threshold
TCC Enable Coolant Temp. Threshold
TCC Disable Coolant Temp. Threshold
TCC Enable Cold Trans. Temp. Threshold
TCC Disable Cold Trans. Temp. Threshold
TCC Enable Hot Trans. Temp. Threshold
TCC Disable Hot Trans. Temp. Threshold
TCC Disable TPS Threshold - Low MPH
TCC Disable TPS Threshold - High MPH
Min TPS to Enable TCC - Low MPH
Min TPS to Enable TCC - High MPH
Low-High MPH Thresh. for TCC TPS Limits
High-Low MPH Thresh. for TCC TPS Limits
Low Neg. Delta %TPS TCC Release Thresh.
Low Neg. Delta %TPS TCC Release Time
High Neg. Delta %TPS TCC Release Thresh.
High Neg. Delta %TPS TCC Release Time
Downshift TCC Release Time
Max Time Between Engine Pulses
Engine Pulses Per Revolution
Input Speed Cal Pulses Per Revolution
Max Time Between Trans Input Pulses
Output Shaft Pulses Per Revolution
Max Time Between Trans Output Pulses
Overdrive Ratio
PROM ID
Tables
ECM Switch Table
ECM Constant Table
Normal Mode Main Line Pressure, 0 - 64 MPH
Normal Mode Main Line Pressure, 64 - 128 MPH
Performance Mode Main Line Pressure, 0 - 64 MPH
Performance Mode Main Line Pressure, 64 - 128 MPH
Main Line Pressure Vs. TPS Vs. Trans. Temp. (2nd)
Main Line Pressure Vs. TPS Vs. Trans. Temp. (3rd)
Main Line Pressure Vs. TPS Vs. Trans. Temp. (4th)
Normal Mode Pressure Offset (psi) Vs. TPS Vs. Gear
Perf Mode Pressure Offset (psi) Vs. TPS Vs. Gear
Down Shift Pressure Modifier 2 -> 1 Vs. MPH
Down Shift Pressure Modifier 3 -> 2 Vs. MPH
Down Shift Pressure Modifier 4 -> 3 Vs. MPH
Line Pressure Modifier In WOT Vs. RPM
Pressure Correction for A/C On Vs. Gear
Engine Breaking Force Motor Pressure Vs. MPH Vs. G
Adaptive Pressure Modifier Vs. Shift Time Error
Adaptive Cell TPS Boundaries
Adaptive Learn TPS Limits Vs. Gear
Normal Mode Upshift/Downshift Vs. MPH Vs. TPS
Performance Mode Upshift/Downshift Vs. MPH Vs. TPS
Desired Shift Time (sec) Vs. %TPS Vs. Gear
Kickdown Up/Down Shift Points
Hot Kickdown Up/Down Shift Points
Shift Ratio Threshold vs Shift
Gear Ratio Limits For Error Diagostics 85, 86 & 87
Garage Shift Press Vs Trans Temp Vs Input Spd, Drv
Garage Shift Press Vs Trans Temp Vs Input Spd, Rev
Rolling Garage Shift Press (psi) Vs. MPH Vs %TPS
Norm Mode Torque Converter Release MPH Vs. TPS
Norm. Mode Torque Converter Apply MPH Vs. TPS
Perf. Mode Torque Converter Release MPH Vs. TPS
Perf. Mode Torque Converter Apply MPH Vs. TPS
Hot Mode Torque Converter Release MPH Vs. TPS
Hot Mode Torque Converter Apply MPH Vs. TPS
TCC Apply/Release Speed at WOT Vs. Gear
TCC Hot Apply/Release Speed at WOT Vs. Gear
TCC Release Rate Vs. %TPS
TCC Apply Operating Point Vs. %TPS
TCC Release Operating Point Vs. %TPS
Operating Point Multiplier Vs. Pressure
TCC Max Time in Release Before Slip Vs. %TPS
TCC Max Time in Release After Slip Vs. %TPS
TCC Apply Rate Vs. %TPS
Minimum TCC Duty Cycle Vs. Torque Pressure
Maximum TCC Duty Cycle Vs. Torque Pressure
Force Motor Current Vs. Desired Pressure

Unless your ready to dive into all these different parameters, better to get a standalone unit. Remember, you've got to wire it all up too.