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About Mike458

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  1. I have a 2017 5.3l Sierra the transmission has had a bad clunk for about a year and half now. Also had a low speed shutter when on the gas poor performance lack of power. I ended up removing the flapper valve in the exhaust before the muffler and so far instant results. Better power smoother acceleration. And so far no clunking. Next step is to remove the muffler and maybe the resonator and just run a straight pipe.
  2. I have removed the flapper valve on my 2017 Sierra and it has seem to solved a lot of issues with my truck. I was haveing a lack of low end power and transmission clunking once I removed the flapper valve it all went away and the truck now runs great! It only has 40k km on it.
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