i just did i 4l80e swap on my brother 99 1500.
He purchased a conversion harness off of the internet. Came with the adapter and new pig tail and pins to install the second speed sensor. we also installed a 243c transfer case that bolted right up to the 4l80e. almost every sensor on the transfer case is different except for the 6 pin plug on the motor. this transfer case only has 1 speed sensor also.
My main issue is that the truck feels like its in high gear. Hardly moves forward. I copied the transmission files from a 12212156 o.s. Truck still did the same thing. Hardly moves forward. I also recieved a P0740 and P0785. I think I have read that i have to shut those codes off to make this transmission function? Is this true? Here is the stock 4l60E tune from his truck. stock 99 5.3 tune.ctz
Any help with be appricatied. thank you