Propshaft off should I replace uj's

I am trying to fix this judder at 40 - 50mph and I have taken the rear prop off as suggested and driven in 4 wheel drive so I know the problem is with the back somewhere. Although I can not see or feel anything wrong with the uj's I suppose the engine/gearbox puts far greater loads on so would you say to replace the uj's anyway as I have the prop off?

They're not expensive so up to you

Yes!

On the sliding Joint should be a mark either side check and make sure they are in line .
Also check not excess play in sliding joint and clean old grease out of it to make sure it has full travel.

If the sliding joint is worn it might be a better idea to replace the whole prop shaft.

Check transfer output and diff pinion for wear, in the side to side/up and down way not rotation, there should be very little if any movement.

whilst there off I would, as long as you know how to do em. Also check if there if there is any slop in the extension joint.

i only replace uj's if they're either sticking or i can feel wear in them

the splines/extension joint should be checked for wear and if considered excessive then just replace the whole prop