Bump steer is the change in toe as the suspension moves through it's travel. My chassis had about 40mm change in toe from top to bottom. You can check yours easy enough. Take a spring off a rear shock and move the suspension through it's full travel and you can see it plain as day.
Some info on some of my mods to the CR Rear end.
CR Rear suspension mods
I make a bump steer kit that fixes the rear geometry with the stock arms too.
The 4130 track rod with rod ends and steel clevis replace the stock track rod on the AU arms. This works on full width and shortened rears.
It improves the rear bump steer no end. Here's the before and after graphs.
Sorry for the Hi-Jack David