1990 Camry DX 4CYL O/D LIGHT FLASHING

Hi,

I just swapped out my blown tranny with one from the junkyard and it runs, shifts etc. Beautifully. However, I noticed last night and this afternoon that my "o/d off" light was flashing intermittently for maybe 5-10 mins then it would go out. It came on and went off under totally different circumstances from which I cannot say that "it happens at exactly X mph". It was flashing on the highway last night then this afternoon when I had the car in park it flashed for a bit then went out again. Anyone have any ideas? Like I said, it shifts and runs great so I am not too worried about this but, any help is greatly appreciated!

Thanks! :D