Is it illegal to sell a car without telling the buyer something's wrong with it?

-I was considering a trade, and i drove an hour to look at it and didn't really like what the other person had so i just ignored him and moved on, that night the slave cylinder went out and now i want to trade so i have something that isnt impossible to shift with (its a 5speed manual) and i'm wondering if that is legal/illegal. and he never test drove it and i had the car posted on craigslist and it said that it had a bad slave cylinder but i dont know if he knows that it's bad and i don't really want to tell him, even though its the right thing to doNo it's not illegal you said there was a problem and you have made it clear as a whistle that your selling the car AS IS and it's really the buyers responsibilty to check the car if they know it has a problem as stated
its amazing but the world has one more turd in it counting you, that cylinder is cheap dummy, get it fixed and move on with your life.sheesh do you work for UPS?
Not illegal, just unethical as far as I'm concerned.