03 suburban soft brakes

[NINFan]

for the last couple of years this truck has had soft brakes. the pads are fine, fluid looks good. 150K on the truck. could it be the vacuum booster? i bled the brakes a while back but it didn't seem to change anything.
any thoughts?

[Cusser]

Is yours drum rears or disc rears? If drums, maybe your automatic adjusters aren't working, you might want to manually adjust those.