http://www.ebay.com/itm/131536023929...%3AMEBIDX%3AIT
they have 4 different sizes including the jack shaft
truck
they will pull apart if you over flex the springs I guess its never happened to me. that truck has a rc4wd 4:1 gru
the other truck has a pmd 4:1 and the cab over has the spi gru. they are steel shafts