Was chatting with a few about this and thought other would benefit too.

When you change tranny filter and fluid, ALWAYS! Use a bottle of line cleaner/tranny flush to clean sediment from the lines (especially inline coolers).

Remove tranny lines from transmission, the bottle will adapt to the line, press to release cleaner until all the tranny fluid is out of the line and the cleaner starts to come out. If a check valve is used, make sure you connect so that the cleaner will flow through all the lines. 

DO NOT run cleaner into transmission.

Let cleaner sit in lines for � an hour or more. Then spray and watch all the "GUNK" come out, keep spraying until clear. Use an air hose to blow lines clear of cleaner before reconnecting lines to tranny. Install new filter and pan gasket, fill with proper amount/type of fluid.

More than once I've had vehicles brought in for tranny service only to find a plugged filter. The owner would say "but I just had the filter and fluid changed." I would then explain how the clean fluid would remove all the sediment from the lines and deposit it in the new filter.

Paul