trans problem?

I have a 1994 540iA with about 111K miles on it. Replaced the engine about 93K miles. I'm having a recent issue with the transmission. For some reason, the "D" icon that is supposed to appear on the dash to indicate the car is in "drive" does not show up all the time. All the other gears are working fine. In fact, if I pull and hold back the gearshift a little bit further from its locked position, then the "D" on the dash reappears. With or without the "D" on the dash, the car is driving fine, shifting smoothly. Sometimes though it sounds like the engine may be a little louder than normal in lower gears. Anybody have any idea what the problem might be? Any help would be appreciated.

prolly the little light being corroded some and not contacting half the time.eng. being replaced at 93k thats a real surprise to me really i've seen them last 200k to 300k infact my 97ti has 207K now.But i'm going to put a 2.5 in it.Prolly normal for it to get a little louder in lower gears its chugging the eng. down some dunno really.