i put a 8.1L/ALLISON TRANS out of a 2001HD silverado 4x4 on a 2006 4x4 silverado.. i keep the 06 BCM. just changued the engine/trans harness and ECM and TCM.. engine is working as it should, transmission is working as it should too.!!

first problem: whe full tank the fuel gage shows empty tank, when empty thank fuel gage shows full tank.. i think the problem is because the 2001 uses other cluster and other fuel pump and maybe the fuel pump sender has diferent signal.. this is noy a big deal.... and oil pressure gaage not working,, im sure its because the 06 oil pressure gage took the siggnal from the serial data and the 2001 takes the signal from the bulb..

second problem.. i cant make the 4x4 work..
it has the 06 module (under the dash), 06 transder motor encoder, and 06 controls.. when i turn the ignition to on position all the lights of the 4x4 controlls will turn on then all turn off and stays off, if i push any button of the 4x4 controller it will not work.. i tried using the 2001 transfer motor encoder and it didnt work,, should i use the 2001 module, controls and transfer motor encoder??

 

The sending unit in the tank is backwards. Switch the two leads around (should be purple IIRC) and it'll be right again. BUT, it would be correct had you not swapped harnesses.

You may need to swap back to the 06 harness to get everything working again. The 01 may have been a ground switched system, while your 06 is a positive switched system. I just don't remember if it was 01 or 02 where they switched back to a positive system.

You may have a bad 4x4 switch, or the bcm may be confused by the transmission/ecm/tcm (because of the polarity issue). Did you get a tune done?

You'd have been better off swapping the connectors (a lot should have been the same) and keeping your 06 harness. I have a feeling you're in for one hell of a head-ache getting it all working properly.

 

WHAT HARNESS? ENGINE HARNESS OR 4x4 HARNESS??

I KNOW IS POSIBLE TO RUN THE 8.1L ENGINE WITH A 06 PCM,, BUT WHAT ABOUT THE TCM?? HOW DO I COMUNICATE THE TCM TO THE ECM???
ITS POSIBLE??

what do you think i should do??

 

Engine harness. As far as the TCM I don't recall if you can run an allison with a different tcm.

I'd call a place that builds harnesses and talk to them. I really don't remember all the EXACT differences between the 01-06 and ally harnesses.
OR, go get yourself a couple of service manuals and start tracing out the wiring diagrams and figure out what you have going on.