I picked up a 2005 LQ9 from a Denali. No harness but it came with a PCM from a 2004 Yukon 4X4, Service Number 12586242. I will be running a 4L80e from a 2005 Silverado and a 1991 GMC NP205 transfer case with a VSS on the output.

I found someone local to build a harness and tune the PCM, but I don’t know what software they use. I would like to be informed when I go over what I want.

Questions?

1. Does it matter what software the tuner has? As an example, does EFI Live give you more options then HP Tuners? Is there anything that can only be done by a GM dealer?

2. I heard I need a segment swap as the PCM should have a tune for a 4L60e and I will be running a 4L80e.

3. I know a 4WD tune is different from a 2WD tune. I know that some PCMs will support a 4WD Low signal (to ground?). This tells the PCM to adjust trans shift points because the transfer case changed the final gear ratio. Is it the PCM or the software? If it’s the PCM, what pin would it be? If it’s software, is it a segment or a operating system? Can the gear ratio for the transfer case be changed? My transfer case gear ratio will be 1.96:1 and the factory setting would be 2.72:1 ratio.


2004 Yukon ECM

 

help...

 

segment swap is not needed... look up SLOW67 he made a thread about it

 

PM him for the complete DIY instructions. Then throw him a small donation for his time and effort...well worth it. I'm using this in my fbody's 4l80e conversion, and it works GREAT.

 

Just burn a 6.0L /4L80 file into it. Should be fine. Just make sure you run the correct harness.

 

I learned a bit since I originally posted this... I found a tuck tune for an LQ4/4L80e (OS of 12592618 with 12591723 calibration), so I'll have that loaded.... What it really comes down to is... When the 4WD LO pin is activated can I change the transfercase ratio? The factory ratio was 2.72:1 and I need it changed to 1.96:1.............. Obviously the info is in the tune some where because it has to calculate for shift points etc...