air vents in back of cab

my 04 silaerado has 2 air vents in back of cab. they let
a lot of muffler noise in cab. any way to shut these off?
thanks

These vents have rubber flaps in them that open to allow cab pressure to escape. This aids in the cab ventilation. If you seal these, you will decrease the performance of the HVAC system. They should not allow an increase in muffler sound entering the cab. Do you have short exhaust dumps ahead of the rear axle?

These vents have rubber flaps in them that open to allow cab pressure to escape. This aids in the cab ventilation. If you seal these, you will decrease the performance of the HVAC system. They should not allow an increase in muffler sound entering the cab. Do you have short exhaust dumps ahead of the rear axle? no they come strait out the back

i know what your talking about but dont know how to fix it. u get road noise and exhaust noise throught them alot. i sound deadened my entire truck and i really notice them now, even with a sub box in front of them blocking some of it you can still hear it. is there any way at all to shut those holes off and still have ventalation?