Air bubbles in tranny fluid

[DukeBoy88]

My truck didn't want to shift into reverse, so I got out and checked the level. the level was ok, as was the color, except it was not quite foamy but full of tiny air bubbles. I know it will do this if it is overfilled, but the level seemed ok. haven't dropped the pan yet, I'll go back outside now and start. If the filter comes loose would that cause this problem? Thanks in advance.

Oh this is on my stock M1008