- Alright so we are all familiar with the mds system. It puts your v8 into a v4 mode when not pressing on gas to save you gas. So my car has been making this rottle noise when mds kicks in. It sounds like when you go back the chain of a bicycle. So i’ve researched it and I believe it might be a bad mds lifter. Thing is if i deaxtivate mds by putting car on manually shift with pedals then mds doesnt kick in and i dont hear it. My question what will happen if i just disable mds with a tuner in order to not hear the ticking sound anymore?