ok... after got my apeix n1 downpipe and muffler on my car. I did a little lauch after that. Some how I lost my AWD later on that day. I now have RWD. I dont even think both my back wheels are going maybe just one of them which is the passenger side. I thought it could be my transfer case, so i had it replace and that didnt fix the problem. Could it be my transmission? or the center viscous coupler? or something else? Please help.