'91 Legend Speedometer works on and off! Answers?

I have a strange problem with my '91 Legend in which sometimes my speedometer works, and other times it doesnt. Now, when my speedometer stops working, the Drive 4 gear (D4) on the dash starts blinking. I am not exactly sure what is casuing the problem but would like to fix it immediately! I have heard rumours that it could be the speed sensor at the transmission?

I had the same flashing light went to transmission shop and had the VSS changed out and it went away