Noise from truck im not sure

[mattro]

hey guys i just recently am having a problem with my '99 4.3l 5sp 4x4 silverado nbs. Seems when i make close to a full turn or tight turn the tires start to chirp. So i checked the air today and it was like 19psi off lol so i filled them to the 50psi it calls for and drove away but when i made a u turn it was still making a sound like i was giving it too much gas and loosing traction but i was taking it easy. Anyways i dont know if this could be related but i put a big load in the bed of my truck full of grass thats been pre-made for lawns it was on a pallet and brought my truck bed a little lower than the front end. It seems something has gotten louder in the truck too it sounds like the tires but i dont remember them making that much noise i could be wrong but at a full stop the sound stops but when i come to a roll not accelerated just in N it makes the sound

 

well any ideas would be great

thanks