Originally Posted by
mightyquickz28
Hey guys, quick question. I have a 96 Z28 with a turbocharged 5.3. I managed to murder my TH350 and so opted for a boneyard 4L80E. I ordered BP automotive plug and play harness to go from the LT1 based wiring to the necessary 5.3 using a 0411 PCM, opting for a 4L60E trans plug at the time. With the TH350, I just had it zip tied out of the way. When I installed the 4L80E I also bought BP automotive plug n play 4L60E to 4L80E conversion harness. I got that all installed last night and flashed the computer to reflect what I wanted. But the weird thing is, sitting still in park/Neutral, the speedometer shows like 23mph. Now, if I start driving, it instantly reflects how fast I'm really going. Otherwise, it drives and shifts fine.
Have any ideas or familiarity with that behavior? Thanks in advance.