4wd popping noises and hard to engage

[Minivek]

Hi, I've got a couple a questions I'd appreciate answers for, I can only put my truck in 4wd (that's HI) when i'm stopped, as soon as i'm rolling I can't do it whereas before I could although it took a couple of tries before working (less than 20 mph), What's wrong with it? It also makes a weird little grinding whirring noise (seems as though it comes from the dash or something) with the 4wd HI light on when it doesn't engage. Also, once the 4wd is engaged I hear a popping noise in the front as I move forward a bit to engage it but it seems to pop on the left before the right side.

I also get a popping noise while turning a little on any surface but it goes away if I turn more(sharper turn) ( I stop turning anymore, before it binds). Also could rusty u-joints in the front be a reason?

Thanks

 

[Blee1099]

Could be some bad auto-hubs. Might be time to switch to some manuals.

 

[Minivek]

all you got to do is get out of the vehicle and switch em on right? Are they really that much more durable?