Basically 1u and 1.1U are interchangable and are for controllibg left and right travel motors. Officially when ordering new controller you have to add machine S/N, so they send you one with correct firmware version. I've seen clients buy from ebay with matching part no on controller, but that number more times than not does not match catalouge part no. Installing is usually quite straightforward, be sure to reset all to defaults and set correct truck type sometimes a bigger reset may be in order when you can't get parameters to match 1=1 on both controllers and you need to reset steering teach in(judit has info in teach in window) replacing lift controller is easier, as it's independent of travel configuration parity.