I have a Cry Baby (original) wah as the first pedal in my chain. The next pedal is a Death by Audio Fuzz War, followed by a Boss Blues driver overdrive. When I click on the Wah, does absolutely nothing if the Fuzz war is on, but it works perfectly fine with the Blues Driver if I bypass the Fuzz war. Anyone have any ideas why this would be?
A lot of fuzz pedals will do this because they produce harmonics on octaves above and below the predominant input frequency. If you're changing that predominant frequency with a parametric filter, the fuzz is working hard to undo it.
The way I remember it, overdrive guys liked wah -> OD, and fuzz guys liked fuzz -> wah. You boost the frequencies you want to OD versus "shaping" the fuzz.