propshaft 4WD problem

HI
last couple of times had the landy out a loud high pitch noise started above 20-25mph, still there when coasting in neutral but dissapeared when put in 4wd,

I removed rear prop this morning, the rear UJ is abit notchy and stiff so assumed this would be problem, i was going to check it by driving without rear prop and in 4wd but landy would nt drive in hi or low, yellow knob stays down, so confused

Q is this normal? does it need the rear prop connected before drive connects to front axle or does it sound like more of gearbox problem

if new prop needed, any recommendations on decent ones

Have you got Free Wheel Hubs?

As I posted the above I remembered last time I had a whistling/squeaking noise, I had one hub engaged, and other free.

no fwh , but when jacked up front, end front prop turning but the wheels are not, suspect broken halfshaft

job sorted turns out it was worn stub axle and drive flange splines on front halfshaft