I'm not sure what he did exactly in the tuning to get the tow/ haul mode to work but it's was one wire on the 0411 connectors that he supplied that I had to hook to a momentary ground. he mentioned that's the gmt800's shifter uses a momentary ground so grabbed one at the junkyard but you have to check the wires on them cause they like to break, about 80% of the gmt800 I check had the broken wires. the shifter have a connector about 6"-8" down the wires so you might want to cut your wires passed that. as for the modification to get it to fit in our steering column, there's a flat spot on one side of the threaded hole that locks it into the column and the gmt800's have that flat spot on the opposite side so I just use a file and started making a flat spot on the other side of the gmt800's shifter until it fits in gmt400 column, but the flat spot you make doesn't need to be as big as the one on the opposite side other wise it fits kinda loose . I'll get pictures if you guys want but it's pretty simple. first thing tho is you need to have your 0411 tuned to do tow/ haul mode