deltadmp

I am new to this forum and found you all just by looking for troubleshooting for mustangs. I own a 99 Ford Mustang, Anniversary Addition. Only has 68,002 miles on it. Knock on wood no major problems. Recently thought I was having problems with my transmission. Car will start will go in reverse but when you push on the gas after putting it in drive, rpm dial will go up but car will not go over 10 miles an hour almost like it will not shift out of first gear. Had the car tested, people think I am crazy now because the car will only do this for me. Go figure. Had some machine put on it and no codes came back. Got in the car this morning car would not go over 10 miles an hour. Drove home in reverse, had it towed long story short still can't find anything wrong with it. Said it could be cadillac convertor(sp?) but they cannot find anything wrong nor will the car do this for them. Car goes into drive and runs perfect. ???? Normally wouldn't be a big deal but I was to start a new job today and from the looks at it I won't be starting tomorrow either. Any help you could provide would be greatly appreciated to this confused mustang owner.