1999 dodge ram

I have a 1999 dodge ram 1500 4x4 i just put a used rear end in it. And now it has a shutter vibration when i pull out and turn. What kind of fluid should i use? should i use a additive?

It has 355 gears and is a locker rearend

thanks

I think it's 75-140 synthetic, and 1 bottle lsd additive