No,as the owner of a LWB M54 (M55),I can confirm it a single line air/hydraulic system,the pedal down to a hyrdrovac is fluid,the rest is air,which is fine when it work’s!After WWII the US Army tested all types & this was the winner!!Something to do with dry brakes when fording & not having to wait for air to build-up under fire,is my best guess.