Do I need to drain/fill trans again?

[JimBee]

My 96 855 auto trans has had at least 4 drain & fills over the last 5 years. It sits for long periods while I drive the other 850. When fully inserted in the tube, the end of the stick is almost horizontal.

Yesterday, I pulled the dip stick and expecting to find nice clean fluid (like it appeared when I changed it last year), the fluid that settled on the top side of the stick looked dark and sooty, while the fluid on the bottom side was nicely clean and pink.

Since the car hasn't been driven much since the last drain and fill, and the fluid was clean then, I'm wondering where that soot came from. What gives?

[greg850r]

A drain and fill 3 times sort of equals a fluid change. When you say 4 done over 5 years do you mean each of the 4 drain & fills was 3 times or once? If once, I would do it again.

[JimBee]

Good point. A full gallon drains each time, so total changed would probably be 4 gallons. The soot on the stick does indicate there's still some present, so maybe needs another round.