My chillchilla used to be quite nice but lately he's been growling and barking? Lol He gets really mean when I come within 2 feet of his whole cage. His pupils are very large and kindof blue. He stands up and lunges his head at me to bite when ever i try to pet him. But his behavior changes drastically in such short time. He will be very angry one second, but once I can pet him, he is very nice and social with me when I hold him. He acts completely unscared until I put him back in his cage. He also grinds his teeth when he is angry. It's a really loud noise and sounds like he's chewing on pebbles. I have never been abusive towards him or hurt him and have not noticed any injuries on him. Do you know what may have caused him to become so aggressive so suddenly?

he could be cage aggressive I have a hamster like that THROWS A FIT when you even try to put food in his cage but once you have him out he is SO sweet.

This is usually due to small cages and lack of handling

Can chinchillas suffer from over active hormones like bunnies? Maybe he is cage aggressive since you mentioned he's fine until you put him back. I would suggest (at least for a smaller animal) to get a gardening or heavy duty oven glove and get him used to your hand being in his cage. The glove will protect from bites. Get him a cave so he can hide of he's scared. If he is truly cage aggressive then he needs to be tamed into knowing you bring the food. Teach him to take treats from your hand too.
Does he have a cooling stone? I know it's hot in many places maybe he's just mad bc he's really warm? Though Chins come from Mexico they require a ceramic cooling stone. I saw these at pet stores but you can probably buy them online cheaper.

You can feel his body all you want, if he has something internally wrong you might not notice until it's too late. Many prey animals are capable of hiding their symptoms till the very end. If he keeps it up, have him looked at.

Good luck!

you dont even need to buy a cooling stone a large sterilized rock works just as well

Same thing. Just make sure it's very clean before giving to to him!

Yeah you actually shouldn't boil them sadly So you have to just scrub it clean before giving it to him and yeah I know its the same thing I was just letting them know you don't have to go out and buy one

Thanks guys He has been acting much better lately. I have an air conditioner in my room to keep it cold for him so I dont think that's the problem. He could just be protective of his cage. But I don't know why he would all of a sudden start doing that. I have been handling him a lot more and he seems to be dOing much better. thank you so much.

You mention that his pupils are "kind of blue" now. That's not normal and sounds like he may be going blind or developing cataracts. He needs to go to the vet. Any drastic behavioral change should always be checked for medical causes.

I didnt notice that I agree if he is losing his sight that can cause aggression I would get him to the vet