Hello, guys and gals. I changed my transmission fluid and noticed that it was like a clear color, instead of red. I refilled it with Castrol DEX/MERC Transmission fluid. My vehicle is a 1991 Mustang 4.9l (ha ha) and 5 speed transmission. It works fine when it is warm, but in the morning when it's cold it is difficult to shift. Is it because I put the wrong fluid or the transmission is wearing out. Thank you for any input guys and gals.