Hey guys, I have a 2006 530i with the ZF transmission with 150K, never changed fluid. I've been getting the shudder from stop through 2nd gear, then it slams into 3rd the. Shifts smooth after 3rd gear. I saw Nathan's video on using the Valvoline Max Life trans fluid. I want to change my fluid. My question is,

Can I do just a drain then fill with new fluid drive it for a while then do a drain, filter change and fill after? What would happen if I only do a fluid only change for now? I hear horror stories of mixing transmission fluids.