It sounds like you have a German built Clark 3 wheel forklift. The Model should be TM15S and serial #TM145... The noise could be a motor or a drive unit bearing for sure but start with the motor. Lift out the battery and remove the motor through the battery compartment. The battery discharge reading problem could be many things. Start with a good test meter at the battery and work your way through the cables and contactor to find the voltage loss. I don't have the manual for that anymore but could probably find it.