How to Diagnose and Silence That Annoying Knock in Your Charger

How to Fix Knocking Noise

A knocking noise from your 2020 Dodge Charger can be alarming, turning a fun drive into a stressful experience filled with worry about potential damage. While the sound can be unsettling, it's often traceable to specific, fixable issues. Based on reports from fellow owners, a common culprit is an aftermarket exhaust system, particularly a 2.75” setup, which can create unexpected contact points and noises. As one owner shared while working on their project: "Got Bored so i took some pics If you didnt figure it out already its not a real SRT, my father, also my partner in this small project of a car, wanted it to look aggressive 😭, next step is a scat hopefully, an actual V8" (source). This pursuit of an aggressive look and sound often leads to modifications that can introduce new problems, like knocking noises. This guide will walk you through diagnosing and silencing that knock based on real-world owner experiences.

Symptoms

The primary symptom is, of course, a knocking or banging sound, but its character and timing provide crucial clues. Owners don't just hear a noise; they experience a cascade of concerns. The sound often manifests as a metallic clunk or bang that seems to come from underneath the vehicle, typically more pronounced during acceleration, when going over bumps, or during sharp turns. It’s not a subtle tick; it’s a pronounced noise that can make you fear something is seriously broken or about to fall off.

This noise directly impacts the driving experience, transforming excitement into anxiety. You might find yourself constantly listening for it, which ruins the grip you feel on the road and the joy of driving. The fear of causing further damage or a catastrophic failure can be paralyzing. In severe cases, a persistent knock from an exhaust component making contact can lead to other symptoms, like unusual vibrations felt through the chassis or even the pedal.

While not directly linked to the knock in every case, owners report other electrical gremlins that add to the overall sense of things going wrong. One owner vividly described a separate but equally frustrating issue: "Dash keeps shutting off, cuts the music, and then rolls down my left window and won’t roll up until it stops when it’s freezing balls outside." (source). This highlights how multiple problems can create a feeling that the car is falling apart, making the knocking noise a central point of focus and frustration.

Most Likely Cause

Based on the parts mentioned and the context from owner discussions, the most likely cause of a knocking noise on a modified 2020 Dodge Charger is an improperly installed or poorly fitting aftermarket exhaust system. The specific mention of a "2.75” exhaust" is key. Owners seeking a more aggressive sound and look frequently undertake exhaust upgrades. However, a larger-diameter pipe (like a 2.75” system compared to a stock one) has less clearance.

This lack of clearance becomes a problem at specific points under the car. The exhaust can make contact with the suspension components, the chassis frame rails, or the body itself. When the engine torques under acceleration or the suspension articulates over a bump, the exhaust pipe can shift and knock against these solid parts. This is not a gentle tap; it's a loud, jarring metal-on-metal bang that resonates through the car. The pursuit of an aggressive aesthetic, as one owner and their father aimed for, often overlooks the precise engineering needed for proper fitment, leading directly to this issue.

How to Diagnose

Diagnosing a knocking noise requires a methodical approach to isolate the source. You'll need a few basic tools: a good flashlight, a set of mechanic's gloves, and a car jack with sturdy jack stands for safe access underneath. Never rely on a jack alone. Start by trying to replicate the noise. Drive the car and note exactly when it happens: during acceleration, braking, turning left/right, or going over bumps. This will point you toward which corner or area of the undercarriage to inspect.

With the vehicle safely raised and supported on jack stands, begin your visual inspection. Focus on the exhaust system first, tracing the entire path from the headers back to the tailpipes. Look for clean, shiny spots on the exhaust pipes or heat shields—these are telltale witness marks where contact has been made. Pay close attention to areas where the exhaust runs near the suspension components, especially the rear control arms and the differential. Also, check where the pipe passes over the rear axle and near the chassis frame rails.

Next, physically check for play. While wearing gloves (parts may be hot or dirty), try to move the exhaust system side-to-side and up-and-down. There should be very little movement; it should be firmly held by its rubber hangers. If you can easily bang it against another component, your hangers may be worn or the system is misaligned. Inspect the plastic liners in the wheel wells as well. A loose liner or one that has been displaced by a larger exhaust pipe can flap and create a knocking or fluttering sound at speed. As one owner succinctly put it after dealing with mods, the goal is often just to make it "look aggressive" (source), but the aftermath requires this kind of detailed troubleshooting.

Step-by-Step Fix

Fixing an exhaust knock is generally a straightforward mechanical task. Here is a step-by-step guide based on the common solutions derived from owner experiences.

1. Gather Tools and Safety First: Ensure you have jack stands, a floor jack, wrenches, sockets, and possibly a rubber mallet. Park on a level surface, engage the parking brake, and chock the wheels opposite the end you're lifting.
2. Safely Raise and Support the Vehicle: Lift the rear (or the entire car, if needed) and place jack stands on designated frame points. Never work under a car supported only by a jack.
3. Locate the Contact Point: Based on your earlier diagnosis, identify the exact spot where the exhaust is hitting. Clean the area around the contact point on both the exhaust and the chassis/suspension part for better visibility.
4. Loosen Exhaust Hangers/Clamps: To allow for adjustment, you may need to loosen the clamps that connect different sections of the exhaust (like at the mid-pipe connection) and/or unbolt the rubber hangers from the body. Don't remove them completely; just loosen enough to allow movement.
5. Reposition the Exhaust: With the system slightly loose, physically shift the exhaust pipe away from the contact point. You may need to twist it or apply gentle pressure with a rubber mallet. The goal is to create a consistent gap (at least half an inch) from any other component.
6. Check Clearance Through Full Range: Have an assistant gently rock the car side-to-side and up-and-down to simulate suspension travel while you watch the clearance. Ensure the exhaust doesn't contact anything through this full motion.
7. Tighten Everything Back Up: Once positioned correctly, tighten all exhaust clamps and re-secure all hangers to their mounts. Double-check that all hardware is tight.
8. Install Additional Protection (If Needed): If clearance is extremely tight but the exhaust is correctly positioned, you can add a heat-resistant wrap to the pipe at the contact point to dampen any potential noise. In some cases, a small dimple can be carefully made in the pipe with a hammer to gain critical clearance.
9. Lower the Vehicle and Test Drive: Carefully lower the car to the ground. Start the engine and listen for any immediate rattles. Then, take a test drive over the same roads and maneuvers that previously caused the knock.
10. Consider Professional Alignment: If the knock persists or you are uncomfortable with the adjustment, a muffler shop can professionally align and potentially modify the exhaust for proper fitment in under an hour.

Parts and Tools Needed

• Jack and Jack Stands: Essential for safe undercarriage access. Never skip these.
• Basic Socket/Wrench Set: For loosening exhaust clamps and hanger bolts. Sizes will vary but typically include 13mm, 15mm, and 18mm.
• Rubber Mallet: For gently persuading the exhaust into a new position without damaging it.
• Flashlight or Work Light: Crucial for seeing dark, tight spaces under the car.
• Mechanic's Gloves: To protect your hands from hot, dirty, and sharp metal.
• Potential Replacement Parts (if found worn):
  • Exhaust Hanger (Rubber Isolator): Mopar part numbers vary, but a common one is 68146250AA. Always verify for your specific model.
  • Exhaust Clamp: For a 2.75" system, you would need a 2.75" diameter band clamp.
  • Heat Shield or Plastic Liner Retainers: If the plastic liners are loose, you may need new push-pin retainers.

Real Owner Costs

The cost to fix a knocking noise varies dramatically between a DIY approach and professional repair, largely depending on the root cause.

• DIY Fix (Exhaust Adjustment): If the issue is simply a misaligned exhaust, your cost can be $0 to $50. This covers the cost of maybe a new clamp or hanger if one broke during adjustment. The primary investment is your time and the tools you already own. This is the path many owners take after modifications.
• Professional Exhaust Alignment: A local muffler shop will typically charge $75 to $150 for labor to inspect, adjust, and re-hang an exhaust system. They have the lifts and expertise to do it quickly. If they need to cut and re-weld a section for proper clearance, the cost could rise to $200-$300.
• Full Part Replacement: If the knocking is due to a failed component like a destroyed motor mount or a severely damaged suspension part (which is less common based on our data), costs soar. For example, replacing a starter (another part mentioned) that has failed and is knocking against the flywheel could cost $400-$700 at a shop for parts and labor. However, the owner data strongly points to exhaust contact as the primary issue, which is far less expensive to resolve.

Prevention

Preventing a future knocking noise is about careful modification and regular checks. If you are installing an aftermarket exhaust, especially a larger-diameter 2.75” system, research brands known for good fitment on the 2020 Charger platform. Read reviews from other owners specifically about installation and clearance issues. Consider having a professional install it, as they can ensure proper alignment from the start.

For any modified car, make it a habit to do a quick visual inspection of the undercarriage every few months or after any incident where you might have hit road debris. Look for new scrapes or shiny spots on the exhaust. Listen for new sounds as they develop; address a small tap before it becomes a loud knock. As one owner reflected on the pride and peril of modifications, the love for the car drives these changes: "It has to be wrong to love a car this much." (source). That love is best shown through diligent maintenance and smart mods.

What Owners Say

Real experiences from DODGE owners:

Owner Experiences

"Been working on my garage that I detail out of. Thought my car looked extra sexy in there." — CarJanitor (source)

"Why TF is my car doing this Dash keeps shutting off, cuts the music, and then rolls down my left window and won’t roll up until it stops when it’s freezing balls outside." — bbooffaa (source)

"Dash keeps shutting off, cuts the music, and then rolls down my left window and won’t roll up until it stops when it’s freezing balls outside." — bbooffaa (source)

Pro Tips from Owners

💡 "It has to be wrong to love a car this much. I got my 23 Super Bee tinted last week (%18 all around)… got it home and my wife says “you should get the headlights and taillights tinted as well, it would just look cool!" — Coping_Skillz (source)

💡 "I got my 23 Super Bee tinted last week (%18 all around)… got it home and my wife says “you should get the headlights and taillights tinted as well, it would just look cool!" — Coping_Skillz (source)

Real Repair Costs

"I work at a dealership, this Widebody Scat came in on trade. I got a sale price of $27.5k it was $30.1k out the door." — GuapGettah (source)

FAQ

Q: How long does it take to fix an exhaust knock? A: If you have the tools and the car safely raised, diagnosing and adjusting a misaligned exhaust can take 1-2 hours for a DIYer. A professional muffler shop can often diagnose and correct it in under an hour.

Q: Can I drive my Charger with a knocking noise? A: It is not recommended. A knocking noise from exhaust contact can lead to worn-through pipes, exhaust leaks, or damage to other components like wiring or brake lines. It's best to diagnose and address it promptly to avoid more costly repairs.

Q: Is this a common issue on the 2020 Dodge Charger? A: It is a very common issue on modified Chargers. The stock exhaust is designed for perfect clearance. When owners install aftermarket systems for more sound or performance—like the mentioned 2.75” exhaust—improper fitment often leads to knocking. It's a frequent topic in owner forums and project car discussions.

Q: DIY vs mechanic - what's recommended for this fix? A: For a straightforward exhaust alignment, a confident DIYer with proper jack stands can tackle this job. It's mostly about loosening, adjusting, and retightening. However, if you lack tools, a safe workspace, or mechanical confidence, a trip to a muffler shop is money well spent. They will fix it quickly and correctly. For any suspected internal engine knock or serious suspension knock, a professional diagnosis is mandatory.

Q: Could the knock be from the starter? A: While the starter was mentioned in the parts data, it is a less common cause for a persistent driving knock. A failing starter can sometimes make a knocking or grinding sound, but this would typically occur only during or immediately after cranking the engine to start it, not while driving. Exhaust contact is a far more likely cause for a knock that happens during acceleration and over bumps.

Q: My dash and windows are acting crazy too. Is this related? A: Almost certainly not. Electrical gremlins like a dash shutting off and windows operating on their own, as one owner experienced, are a separate issue typically related to body control modules or wiring harness problems. "Why TF is my car doing this Dash keeps shutting off, cuts the music, and then rolls down my left window..." (source). While frustrating, this requires a different diagnostic approach focused on the electrical system, not the undercarriage.