when he does it, what do you do? do you back off or correct him? the second any of our dogs growl they get a sharp "NO" so they know i won't tolerate it. how hard do you pull on him when you grab his collar? if he reacts like this every time you grab his collar maybe you are hurting him unintentionall y, or you or someone else may have accidentally in the past and it makes him uncomfortable now. have you taught him the "come" command? maybe you could use it instead of grabbing him. do you only grab his collar when you try to get him off the couch or to take him outside, or is this just the only time he reacts? if this only happens in these two situations, he may need an attitude adjustment, and you could try the NILIF (nothing in life is free) training, or maybe just a lot of obedience work with him.