The transmission is shifting hard and has a thumping impact.
Hi there. Though there are many issues that can cause the transmission to shift hard in your Cadillac there are some common problems. If the check engine lightis not on, the problem can be caused by a bad engine or transmission mount. If one of these fail then the engine and/or transmission can move when the shifting occurs causing a hard shift. If the mounts are fine then the problem is usually pressure related from an internal problem or a pressure solenoid failure. If the mounts are fine then the fluid should be drained and inspected for signs of metal. Any metal in the fluid indicates a serious internal issue. This problem is best left to certified mechanic that has the tools to check the transmission properly.