mine has been doing this since I got it. its got nothing to do with oil, its a safety feature if ud like to call it that so that if u accidently knock it into R whilst driving it dosent go into the reverse gear, and you can put it back into drive. now that is what I have been told, soooooo it may be a good old spin of sh*t. im gonna get a tranny service over the week ond now!!!