I am in the process of swapping an E38 w/ T43 (6L80E) into a 99 Silverado.
Truck is running alright, went out for first test drives.
To be able to use the existing cluster we left the original ECM in the truck and wired
the needed signals into it.
The following issues are remaining:
- MIL circuit - probably due to both ECMs wired to the same MIL lamp
- Charging system - need to wire "generator turn on signal" to old ECM
- OBD connector: wired both ECMs into the same OBD connector. EFILive will however not let me connect to the E38 if signals for the LS1B are present
- VSS - due to the lack of an external VSS sensor on the 6L80E I have not figured out how to get the VSS signal into the LS1B ECM.
Tried to wire the E38 C1, pin 57 into the VSS input but the speedo is not moving.
I there any other way to get this to work? Do I need to change the calibration?
We really want this to work as the VSS signal is also needed for the ABS system...
I hope there is a way other than adding an VSS sensor and reluctor somewhere to the driveshaft.

Currently we always need to disconnect the battery and then start to be able to get the Tranny to shift. If the ignition is cycled the transmission will not shift right...I know this sounds a little odd, but this is what we have observed. There are no DTCs from the transmission.