Can a bad cv joint make noise going straight or slowing down?

Yes it can, and if it is, trust me this just happened to me, you got to fix it as fast as possible. If you just blow it off you can be looking at some dire consequences. 1) The CV joint can abruptly fail and you will lose all drive power, if one CV joint goes your differential will NOT power the other wheel. 2) if you are driving at a good click, the RPMs on the CV joint will cause it to fail and the CV joint will tear up the inside of your engine. 3) In rare occasions the failure could cause one of your wheels to lock up and you will lose most if not all control of your car. Moral of the story is do not drive any long distances from your house on a bad CV joint unless you have money to blow on a tow. You can buy a replacement CV joint at any Auto Parts store for 75-125 dollars, I advice to get one with a lifetime warranty. DO NOT DRIVE ON A BAD CV JOINT!