differential problums 1994 GMC

[vanrodd]

hi i bought a 1994 GMC searra 1500 2 wheel drive a few months ago from a towing co. i noticed when i make hard turns the rear tires make screaching noises like im going 70 around the corner but im only going 15 mph it felt like full posi so i jacked up the truck and spun the tire and both turned the same direction so i looked for a switch on the dash and could not find one i have 33x11.5 tires on the truck and i dont think this could be doing my rearend any good i tride to find out what rearend it has all i could find on it was no. 5822 and xpkk1462 and gmd and theres nothing in my glove box anyone have any ideas. thanks

[maxwedge]

Glove box code for the locking diff is G80.