{
    "lazyNodes": false,
    "abFitnotesFlag": false,
    "abCrawlReviews": true,
    "productOptionsCookie": false,
    "orderDelayFlag": false,
    "skipSessionCookie": false,
    "covidMessage": false,
    "fullTitleCookie": false,
    "nrLoggerCookie": true,
    "checkoutReviewCookie": false,
    "productOptionSeqCookie": false,
    "maintenanceFlag": false,
    "bufferETACookie": false,
    "multiShippingDiscountFlag": false,
    "newFitmentFlag": false,
    "surveyOptInFlag": true,
    "crossSellFlag": false,
    "skuMappingFlag": false,
    "paySplitCookie": false,
    "callDisableFlag": true,
    "zipPaymentFlag": "c",
    "hassleFreeReturn": true,
    "lifetimeReplacement": true,
    "cpn_off": false
}
2022 GMC Sierra 3500 HD

2022 GMC Sierra 3500 HD Exhaust Systems

Refine by:

Shop Catalog

Showing 1 - 14 of 14 results
Sort by:
Filter-Back Exhaust System, 8, 6.6, Made of Aluminized Steel, Armor Lite Series
Part Number: M79S6059AL
Guaranteed to Fit
$364.99
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive, Excludes Dual Rear Wheel Configurations
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Rear Wheel Drive, Excludes Dual Rear Wheel Configurations
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive, Excludes Dual Rear Wheel Configurations
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L 82.2 in. Bed, Extended Cab Pickup, Rear Wheel Drive, Excludes Dual Rear Wheel Configurations
  • 2022 GMC Sierra 3500 HD Pro 8 Cyl 6.6L 82.2 in. Bed, Extended Cab Pickup, Rear Wheel Drive, Excludes Dual Rear Wheel Configurations
Product Details
Material : Made of Aluminized SteelSystem Type : Filter-BackQuantity Sold : KitWarranty : 3-year MBRP limited warrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Series : Armor Lite SeriesMain Piping Diameter : 4 in. Main PipeRecommended Use : OE UpgradeProduct Fit : Direct Fit
Filter-Back, Exhaust System, 6.6L, 82.2 in. Bed, Extended Cab Pickup, Four Wheel Drive, Made of Aluminized Steel, Armor Lite Series -
Part Number: M79S60610AL
Guaranteed to Fit
$439.99
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Rear Wheel Drive
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L 82.2 in. Bed, Extended Cab Pickup, Four Wheel Drive
  • 2022 GMC Sierra 3500 HD Pro 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Rear Wheel Drive
Product Details
Material : Made of Aluminized SteelSystem Type : Filter-BackQuantity Sold : KitWarranty : 3-year MBRP limited warrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Series : Armor Lite SeriesMain Piping Diameter : 5 in. Main PipeRecommended Use : OE UpgradeProduct Fit : Direct Fit
Filter-Back Exhaust System, 8, 6.6, Made of Stainless Steel, Armor Pro Series
Part Number: M79S60610409
Guaranteed to Fit
$559.99
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Rear Wheel Drive
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L 82.2 in. Bed, Extended Cab Pickup, Four Wheel Drive
  • 2022 GMC Sierra 3500 HD Pro 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Rear Wheel Drive
Product Details
Material : Made of Stainless SteelSystem Type : Filter-BackQuantity Sold : KitWarranty : Lifetime MBRP limited warrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Series : Armor Pro SeriesMain Piping Diameter : 5 in. Main PipeRecommended Use : OE UpgradeProduct Fit : Direct Fit
DPF-Back Exhaust System, 8, 6.6, Made of Stainless Steel, Pro Series
Part Number: M6617870
Guaranteed to Fit
$839.00
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L DIESEL, Crew Cab Pickup, Four Wheel Drive, Single Passenger Side Rear Exit
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L DIESEL, Crew Cab Pickup, Four Wheel Drive, Single Passenger Side Rear Exit
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L DIESEL, Crew Cab Pickup, Four Wheel Drive, Single Passenger Side Rear Exit
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L DIESEL, Crew Cab Pickup, Rear Wheel Drive, Single Passenger Side Rear Exit
  • 2022 GMC Sierra 3500 HD Pro 8 Cyl 6.6L DIESEL, Crew Cab Pickup, Four Wheel Drive, Single Passenger Side Rear Exit
Product Details
Material : Made of Stainless SteelSystem Type : DPF-BackQuantity Sold : KitWarranty : Lifetime Magnaflow Limited WarrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Series : Pro SeriesExit Location : Exit: After Rear Tire (Passenger Side)Main Piping Diameter : 5 in. Main PipeRecommended Use : OE UpgradeProduct Fit : Direct Fit
Cat-Back, Exhaust System, 8 Cyl 6.6L, Standard Cab Pickup, RWD, Made of Stainless Steel, Outlaw Series -
Part Number: F13818112
Guaranteed to Fit
$858.95
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L Crew Cab Pickup, 4WD
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L Cab & Chassis, RWD
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L Crew Cab Pickup, 4WD
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L Crew Cab Pickup, 4WD
Product Details
Material : Made of Stainless SteelSystem Type : Cat-BackQuantity Sold : KitWarranty : Lifetime Flowmaster Limited WarrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Series : Outlaw SeriesExit Location : Exit: Dual Split RearMain Piping Diameter : 3.5 in. Main PipeRecommended Use : OE UpgradeProduct Fit : Direct Fit
Exhaust System, 8 Cyl 6.6L, Rear Wheel Drive, DIESEL, Extended Cab Pickup; Installation Hardware Included; Replacement System, Made of Aluminized Steel -
Part Number: BO1060751
Guaranteed to Fit
$865.00
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L Four Wheel Drive, DIESEL, Crew Cab Pickup; Installation Hardware Included; Replacement System
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L Rear Wheel Drive, DIESEL, Extended Cab Pickup; Installation Hardware Included; Replacement System
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L Four Wheel Drive, DIESEL, Crew Cab Pickup; Installation Hardware Included; Replacement System
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L Rear Wheel Drive, DIESEL, Crew Cab Pickup; Installation Hardware Included; Replacement System
  • 2022 GMC Sierra 3500 HD Pro 8 Cyl 6.6L Rear Wheel Drive, DIESEL, Extended Cab Pickup; Installation Hardware Included; Replacement System
Product Details
Material : Made of Aluminized SteelQuantity Sold : KitWarranty : 2-year BRExhaust limited warrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Main Piping Diameter : 4 in. Main PipeRecommended Use : OE ReplacementProduct Fit : Direct Fit
Cat-Back, Exhaust System, 8 Cyl 6.6L, Crew Cab Pickup, RWD, Made of Stainless Steel, American Thunder Series -
Part Number: F13817933
Guaranteed to Fit
$972.95
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L Crew Cab Pickup, 4WD
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L Cab & Chassis, RWD
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L Crew Cab Pickup, 4WD
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L Crew Cab Pickup, 4WD
Product Details
Notes : 18 in. Muffler Body Length; 3 in. Muffler Inlet Diameter; 3 in. Muffler Outlet Diameter; 24 in. Muffler Overall Length; Black Muffler Color; Painted Muffler Finish; Centered Muffler Inlet Location; Dual Outlet Muffler Outlet Location; Oval Muffler Shape; Reflection Muffler Type; Aggressive/Moderate Sound Level; Angle Tip Cut; Cut Tip Edge Style; Polished Tip Finish; Embossed Tip Logo; 304 Stainless Tip Material; Round Tip Shape; Double Wall Tip StyleMaterial : Made of Stainless SteelSystem Type : Cat-BackQuantity Sold : KitWarranty : Lifetime Flowmaster Limited WarrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Series : American Thunder SeriesExit Location : Exit: After Rear Tire (Dual Split Side)Main Piping Diameter : 3 in. Main PipeRecommended Use : OE UpgradeProduct Fit : Direct Fit
Filter-Back Exhaust System, 8, 6.6, Made of Stainless Steel, Black DPF Series
Part Number: M6617072
Guaranteed to Fit
$1,043.00
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L DIESEL, Crew Cab Pickup, Four Wheel Drive, Single Passenger Side Rear Exit
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L DIESEL, Crew Cab Pickup, Four Wheel Drive, Single Passenger Side Rear Exit
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L DIESEL, Crew Cab Pickup, Four Wheel Drive, Single Passenger Side Rear Exit
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L DIESEL, Crew Cab Pickup, Rear Wheel Drive, Single Passenger Side Rear Exit
  • 2022 GMC Sierra 3500 HD Pro 8 Cyl 6.6L DIESEL, Crew Cab Pickup, Four Wheel Drive, Single Passenger Side Rear Exit
Product Details
Notes : 13 in. Tip Length; 6 in. Tip Diameter; Stainless Steel Tip Material; Black Coated Tip Finish; Welded-On, Single Wall, Angle Cut, Rolled Edge, Intercooled Tip Type; (0) Muffler Quantity; Band Clamp Type; Bolt-On and Clamp-On Inlet Connection TypeMaterial : Made of Stainless SteelSystem Type : Filter-BackQuantity Sold : KitWarranty : Lifetime Magnaflow limited construction warranty and 1-year Magnaflow limited finish warrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Series : Black DPF SeriesExit Location : Exit: Rear (Passenger Side)Main Piping Diameter : 5 in. Main PipeRecommended Use : OE UpgradeProduct Fit : Direct Fit
Cat-Back, Exhaust System, 6.6L, 82.2 in. Bed; Crew Cab Pickup; 172.0 in. Wheelbase; Except Vehicles With Dual Rear Wheels, Made of Stainless Steel, S-type Series -
Part Number: B25140833
Guaranteed to Fit
$1,233.99
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L 82.2 in. Bed; Crew Cab Pickup; 172.0 in. Wheelbase; Except Vehicles With Dual Rear Wheels
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L 82.2 in. Bed; Crew Cab Pickup; 172.0 in. Wheelbase; Except Vehicles With Dual Rear Wheels
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L 82.2 in. Bed; Crew Cab Pickup; 158.9 in. Wheelbase; Except Vehicles With Dual Rear Wheels
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L 82.2 in. Bed; Crew Cab Pickup; 172.0 in. Wheelbase; Except Vehicles With Dual Rear Wheels
  • 2022 GMC Sierra 3500 HD Pro 8 Cyl 6.6L 82.2 in. Bed; Crew Cab Pickup; 158.9 in. Wheelbase; Except Vehicles With Dual Rear Wheels
Product Details
Material : Made of Stainless SteelSystem Type : Cat-BackQuantity Sold : KitWarranty : Million-mile Borla limited warrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Specialty Part : Performance Part by JCWSeries : S-type SeriesExit Location : Exit: Truck SideMain Piping Diameter : 3.5 in. Main PipeRecommended Use : Performance ReplacementProduct Fit : Direct Fit
Cat-Back, Exhaust System, 8 Cyl 6.6L, GAS, Extended Cab Pickup, Four Wheel Drive, Single Passenger Side Rear Exit, Made of Stainless Steel -
Part Number: M6619524
Guaranteed to Fit
$1,235.00
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L GAS, Crew Cab Pickup, Four Wheel Drive, Single Passenger Side Rear Exit
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L GAS, Crew Cab Pickup, Four Wheel Drive, Single Passenger Side Rear Exit
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L GAS, Crew Cab Pickup, Four Wheel Drive, Single Passenger Side Rear Exit
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L GAS, Extended Cab Pickup, Rear Wheel Drive, Single Passenger Side Rear Exit
  • 2022 GMC Sierra 3500 HD Pro 8 Cyl 6.6L GAS, Crew Cab Pickup, Rear Wheel Drive, Single Passenger Side Rear Exit
Product Details
Material : Made of Stainless SteelSystem Type : Cat-BackQuantity Sold : KitWarranty : Lifetime Magnaflow Limited WarrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Recommended Use : OE Upgrade
Cat-Back Exhaust System, 8, 6.6, Made of Stainless Steel, S-type Series
Part Number: B25140833BC
Guaranteed to Fit
$1,266.99
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L 82.2 in. Bed; Crew Cab Pickup; 172.0 in. Wheelbase; Except Vehicles With Dual Rear Wheels
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L 82.2 in. Bed; Crew Cab Pickup; 172.0 in. Wheelbase; Except Vehicles With Dual Rear Wheels
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L 82.2 in. Bed; Crew Cab Pickup; 158.9 in. Wheelbase; Except Vehicles With Dual Rear Wheels
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L 82.2 in. Bed; Crew Cab Pickup; 172.0 in. Wheelbase; Except Vehicles With Dual Rear Wheels
  • 2022 GMC Sierra 3500 HD Pro 8 Cyl 6.6L 82.2 in. Bed; Crew Cab Pickup; 158.9 in. Wheelbase; Except Vehicles With Dual Rear Wheels
Product Details
Material : Made of Stainless SteelSystem Type : Cat-BackQuantity Sold : KitWarranty : Million-mile Borla limited warrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Specialty Part : Performance Part by JCWSeries : S-type SeriesExit Location : Exit: Truck SideMain Piping Diameter : 3.5 in. Main PipeRecommended Use : Performance ReplacementProduct Fit : Direct Fit
Filter-Back Exhaust System, 8, 6.6, Made of Stainless Steel, Armor Pro Series
Part Number: M79S6059304
Guaranteed to Fit
$489.99
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive, Excludes Dual Rear Wheel Configurations
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Rear Wheel Drive, Excludes Dual Rear Wheel Configurations
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive, Excludes Dual Rear Wheel Configurations
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L 82.2 in. Bed, Extended Cab Pickup, Rear Wheel Drive, Excludes Dual Rear Wheel Configurations
  • 2022 GMC Sierra 3500 HD Pro 8 Cyl 6.6L 82.2 in. Bed, Extended Cab Pickup, Rear Wheel Drive, Excludes Dual Rear Wheel Configurations
Product Details
Material : Made of Stainless SteelSystem Type : Filter-BackQuantity Sold : KitWarranty : Lifetime MBRP limited warrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Series : Armor Pro SeriesRecommended Use : OE UpgradeProduct Fit : Direct Fit
Filter-Back Exhaust System, 8, 6.6, Made of Aluminized Steel, Armor BLK Series
Part Number: M79S6059BLK
Guaranteed to Fit
$514.99
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive, Excludes Dual Rear Wheel Configurations
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Rear Wheel Drive, Excludes Dual Rear Wheel Configurations
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive, Excludes Dual Rear Wheel Configurations
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L 82.2 in. Bed, Extended Cab Pickup, Rear Wheel Drive, Excludes Dual Rear Wheel Configurations
  • 2022 GMC Sierra 3500 HD Pro 8 Cyl 6.6L 82.2 in. Bed, Extended Cab Pickup, Rear Wheel Drive, Excludes Dual Rear Wheel Configurations
Product Details
Material : Made of Aluminized SteelSystem Type : Filter-BackQuantity Sold : KitWarranty : 1 year MBRP limited warrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Series : Armor BLK SeriesRecommended Use : OE UpgradeProduct Fit : Direct Fit
Cat-Back, Exhaust System, 6.6L, GAS, 82.2 in. Bed, Crew Cab Pickup, Rear Wheel Drive, Made of Stainless Steel, Armor Pro Series -
Part Number: M79S5093304
Guaranteed to Fit
$1,004.99
Vehicle Fitment
  • 2022 GMC Sierra 3500 HD Denali 8 Cyl 6.6L GAS, 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive
  • 2022 GMC Sierra 3500 HD SLE 8 Cyl 6.6L GAS, 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive
  • 2022 GMC Sierra 3500 HD AT4 8 Cyl 6.6L GAS, 82.2 in. Bed, Crew Cab Pickup, Four Wheel Drive
  • 2022 GMC Sierra 3500 HD SLT 8 Cyl 6.6L GAS, 82.2 in. Bed, Crew Cab Pickup, Rear Wheel Drive
  • 2022 GMC Sierra 3500 HD Pro 8 Cyl 6.6L GAS, 82.2 in. Bed, Extended Cab Pickup, Rear Wheel Drive
Product Details
Material : Made of Stainless SteelSystem Type : Cat-BackQuantity Sold : KitWarranty : Lifetime MBRP limited warrantyProp 65 Warning :

Warning SymbolWARNING: This product can expose you to chemical which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.

Series : Armor Pro SeriesRecommended Use : OE UpgradeProduct Fit : Direct Fit
Page 1 of 1 | Showing 1 - 14 of 14 results

Popular Products

Helpful Automotive Resources

Engine Knocking Sound: What Does it Mean?
Engine Knocking Sound: What Does it Mean?You may notice that the noise becomes more frequent when engine speed is increased, especially if the sound is due to a failed bearing. What Does a Knocking Noise in the Engine Mean?