FC_Technik

I have recently bought my first 91' fc3s from a cousin of mine. Maybe just a 2 days ago as my bro and i were coming to a stop as he shifted down and put it in neutral the car made a thump noise. After that we kept driving home and everything seemed all good. I'm not to sure whats the problem is and am afraid maybe there might be a clutch or transmission problem or something could be loose any help would be much appreciated.