I have read a lot of posts on transmissions both manual and auto lately and I have a question about my automatic on my 1987 van.  The tranny was rebuilt about 10 yrs ago by my then mechanic from top to bottom and it is doing great. My question is: Should I change the fluid and filter or, leave it alone. the fluid still is red just like it came out of the bottle and it never needs topping up. 

My Dad always had the idea that "If it ain't broke, don't fix" However I also believe in preventative matience.

Waiting for your great advice here.

Chris S.