I'm going to assume that when you say 'i just installed my 4 link' that you have just installed adjustable trailing arms / panhard rod.
The only reason it would vibrate alot is if all the settings were out of whack.
Make sure both the upper trailing arms have exactly the same length, and the lower pair too.
Infact just try adjusting them to the stock lengths and see if the problem is still there.
Also make sure your diff is centred.