After scanning through several forums before buying a Benz,I found myself coming back to this one.I was looking at a one owner 1997 C280 6 Cylinder with 127K.After some thought,I was able to make a deal and purchase the car. Now,that has required me to go from casual reader of this forum,to actually being a member. I'm pretty happy with the car so far,but I'm having a small problem. I'm sure it's been covered here before,but I want to share the symptoms the car is having and ask some questions.When I bought the car,the ABS light was (and still is)on. On a 200 mile road trip this week I was cruising down the interstate and I thought I felt the car down shift out of over drive for just a second. It happened so quick,and I was pretty much thinking of other things when it happened,so I wasn't sure. Later in the trip when leaving from a stop light,the car downshifted into first gear after I was rolling.It must have started out in second then went to first with a jolt. Now,the rest of my day was ruined because I was wondering if the car had a major tranny problem developing and was going to die on the trip back home. The trip back home was smooth other than one rather firm downshift when coming to a stop. Just one. No other check lights ever illuminated. The car had a new battery installed just before I bought it. Now,my first question is...Where do I start? I have a generic ODB reader.I do not have the pin plug to check the ABS code. Do I need to get one? Will my reader do any good if I had it? It will read engine codes on the car. There is not local mechanic that I would trust to look at the car and give me a heads up on what it may be. Just a dealer in the next town. I have no doubt that I can solve this issue myself with the right guidance. I thank you all in advance for any advice.