Davecook1

iTrader: (1)

I have a 00 gmc sierra sclb 2wd ls1 5.7 an i just recently swapped in a 4l80 with the nelson harness. trans has a stage 3 jakes kit an circle d converter multi disk. had it segment swapped an now randomly it shifts an drives fine then sometimes it will lock up at 25 or 30mph instead of 50 where its set at. could wires be lose somewhere? ill shut the truck off let it sit an go back to it an it will drive fine an lock up the way it is suppose to at 50. any reason why it would do this? The first time it did this it through a p0121 code
-Thanks in advance

TrendSetter

not sure but you should double check the trans tables. there are a shitload of them and its tricky making them all play together. you have to make sure they dont cross each other and all that. tuning these transmissions is a bit of a pain.
theres a pretty good excel sheet on the efilive forum for plotting everything and making sure they are at least close.