Originally Posted by ArthurJGuy
I would think again, I have fought it in court and won as have many others.
The minor horsepower gain that a cat delete would cause, is the same gain you get when it gets cold outside. He has to directly prove that the removal of the cat caused not only an engine failure, but in your example a driveline failure and there is no link between the two at all. Not only that but catalayic converters, being emissions and not performance based, have their own warranty mandated by the government.
I have done a MM action and they are not obligated to warranty something they did not sell you. By changing the power level of the car you have altered the loads on the engine and drivetrain to something that they did not sell and they are not obligated to warranty it unless it can be shown that the increase was of no significance. The argument of significance is held to the yardstick of the variability of the power level put out by the engine as stock. Exceed that and the car has become something they did not sell and they have no obligation to provide warranty on something they did not sell. Actually go to court which most MM actions don't and they will have a whole passel of graphs and assorted data to trot out and the court will accept this as truth until you prove them wrong. Getting on the stand and saying liar liar pants on fire isn't going to cut it, you have to have your own data to counter theirs.
The loss of warranty will either be case by case or of the drivetrain as a whole while the remainder of the car will remain under warranty. This is something that is provided for under MM along with right to seek costs and many other things which I cant recall. Notice I said the right to seek costs, there is no guarantee of getting them. The total warranty can only be voided if the car meets a few specific criteria such as odo tampering, salvage title, altered so completely as to change its fundamental use to something other than what it was sold for. There are a few more but its been almost 10 years since my lawyer explained all this stuff to me.
I'm no attorney and I know that state law can play a large factor in these actions but what I know says what your saying is not true. My attorney actually laughed at me when I said pretty much what you posted which was what I believed at the time.