Hey guys new to the site. I am sure I'm not the first to ask this. I have a 98 K1500 4l60e truck. swapped a 4l80e into it. i am having issue i believe its electrical. everything is bolted in and working. for some reason it doesn't have 1st gear or OD. i used a harness i got online then noticed it says LS. but it also said it would work for 96-up. according to the instruction you use pins 22 and 23 on an 80 pin connector. my truck doesn't have an 80 pin. i have the ( red, blue, white, and black ) pcm. any info you guys would have would be greatly appreciated!
majority of the info i can find is all LS stuff. truck has a vortec 5.7.

 

What harness did you buy? LS and the "black box" ECU I'm pretty sure are different.

You don't really need the harness TBH. Just change the pins on the big gray case connector on the transmission, then add the second speed sensor, and finally, repin the connectors on the ECU end. It sounds harder than it is.

I suppose since you already have the harness, try looking up a C/K2500 that came with the 4L80e to see where the ECU pins went.

And you will still need to get an ECU reflash for the different transmission.

I hope this helps.👍