Ok so my truck has 160k on it with the original 4l60e and while in the midst of pulling my motor I noticed that the fluid is pretty ugly . I have put 90k on this truck my self in the past 4 years without a service and to be honest im not sure if it has ever had one. It shifts fine, only once in a while will i get a little slip and when shifting from first I get this spooling down turbine nosie That being said what is your guys opinion should I change out the fluid ( I know that on the older tranies it does more harm than good ) or should I top it off and run her till she screams like a girl? Thanks