mare

Hello. The knocking starts when i brake at low speeds(50km/h and below) and mostly before the car stops. Every time at front wheels(left and right). Knocking is more intense when i'm braking downwards(video).Sometimes when i brake till the car stops and then when i'm taking off it knocks a little bit. The knocking is coming somewhere from the brakes area. When i'm reversing and then braking, no knocking at all. Does somebody have a clue what cause this knocking?
https://www.youtube.com/watch?v=DSrS84-eKKU&feature=youtu.be

I can't figure out which code is for LSD and which for open diff. I see on eBay these three codes. M58, M59, M66,... I'm buying only a differential so i have to be sure that is LSD.