I have a 2001 chevy blazer 4.3L. No ZR1 package. Going upstate for the weekend my front Differential starting making nosie. By the time the weekend was over so was the front differential. (had to call in a favor and got towed home.) I want to replace the front differential. I''ve been checking the local salvage yards, but i don't know the difference between a ZTN or a ZTU differential. I know I have a GU6 which is a 3:42 according to the sticker in the glove box. It has three buttons on the dash 2 HI, 4 LO, 4 HI. Can someone help please. I want to replace it with the correct unit.