A903 issues

Your shift problem could be syncro ring related but the whirling noise when the clutch is not depressed can only be transmission bearing related. When the clutch is depressed & the car is at standstill, everything inside the transmission stops turning. Either the input bearing is shot or the needle rollers on the countershaft have worn the case hardening on the countershaft itself. Worn slider dogs or interlocks could be the reason for the trans wanting to jump out of gear, or indeed maladjusted shifter rods could be another reason.