How to Fix Your 2020 Silverado's Shudder and Knocking Noise

How to Fix Transmission Issue

For 2020 Chevrolet Silverado owners, transmission-related problems can manifest as unsettling noises and vibrations, often pointing to specific mechanical failures. Based on real owner experiences, the root cause frequently involves components like the flywheel or torque converter, compounded by maintenance history. As one owner, open_road_toad, summarized after extensive research: "From what I gather it’s a combination of problems (lack of proper maintenance and weak converter)." This guide will walk you through identifying, diagnosing, and resolving these issues using data-driven solutions from actual Silverado owners.

Symptoms

Owners of the 2020 Silverado report a distinct set of symptoms that signal transmission or driveline trouble. The most commonly described issue is a pronounced shudder or shaking, often felt through the steering wheel, seat, or floorboard. This is frequently called a "torque converter shudder" and typically occurs at specific speeds, like during highway cruising or light acceleration, feeling like the truck is driving over rumble strips.

Another prevalent symptom is a persistent knocking or tapping sound coming from the floorboard area. This noise can be intermittent or constant and often leads owners to suspect suspension issues initially. As isaacvargas760 shared after a long diagnostic journey: "After months of hearing a knocking/tapping sound coming from the floorboard area, I finally think the issue is solved." This noise is a key indicator of a failing component like a motor mount or a loose flywheel/flexplate.

Some owners also describe phantom shudders—brief, unexpected vibrations that come and go. Combined with the physical shuddering and knocking sounds, these symptoms create a driving experience that feels unreliable and can cause significant concern about a major failure. It’s important to note that these symptoms are often misdiagnosed; one owner spent significant money on transmission work and spark plugs only to find the core issue was a cracked spark plug from improper installation, highlighting the need for careful diagnosis.

Most Likely Cause

Based on aggregated data from nearly 100 owner discussions, the primary cause of these shuddering and knocking issues in the 2020 Silverado is a failed or failing torque converter, often in conjunction with a defective or cracked flywheel (flexplate). The torque converter is the hydraulic coupling between your engine and transmission, and a weak or failing unit cannot properly manage the transfer of power, leading to the characteristic shudder. This is compounded by what owners identify as a general lack of robust design in these components.

The problem is frequently described as systemic. The torque converters in these applications are noted for being a weak point, and when they fail, they can cause collateral damage or be symptomatic of other issues. A cracked or loose flywheel will create a distinct metallic knocking or tapping sound, as it no longer provides a stable connection between the engine and the transmission. This dual failure mode—a weak converter and a problematic flywheel—creates the combination of shuddering and knocking that plagues many owners. As the data suggests, simply replacing one part without inspecting the other may not lead to a permanent fix.

How to Diagnose

Accurate diagnosis is crucial to avoid unnecessary and expensive repairs. You will need a basic mechanic's tool set, a floor jack and jack stands, and a helper.

Step 1: Pinpoint the Symptom. Drive the truck and note exactly when the symptoms occur. Is the shudder felt at 45-55 mph under light throttle? Does the knocking sound happen at idle, during acceleration, or over bumps? Record these details.

Step 2: Visual and Physical Inspection (Safely). With the truck safely raised on jack stands and supported, perform a visual inspection. Check the engine and transmission mounts for excessive cracking, separation, or collapse. A bad motor mount can cause knocking and shifting sensations.

Step 3: Inspect the Flywheel/Flexplate. This is a critical step. You or a mechanic will need to inspect the area between the engine and transmission. A common method involves removing the starter motor to gain a visual line of sight to the flywheel. Look for visible cracks, shiny spots indicating metal-on-metal contact, or loose bolts. A stethoscope or long screwdriver held to the ear (carefully, with the engine off) can help isolate a tapping noise to the bellhousing area when the engine is running.

Step 4: Professional Scan and Road Test. A transmission shop can perform a road test while monitoring transmission data like torque converter clutch (TCC) slip speed. A shudder correlated with erratic TCC slip data is a classic sign of torque converter failure. They can also rule out misfires (which can feel like a shudder) by checking engine data, which was the culprit for one owner who had cracked spark plugs.

Step-by-Step Fix

The definitive fix, as reported by owners who resolved their issues, involves replacing the faulty torque converter and inspecting/replacing the flywheel. Here is a step-by-step guide based on successful owner repairs.

1. Gather Parts and Prepare. Secure a high-quality replacement torque converter. Many owners recommend an upgraded, remanufactured unit over a standard OEM or junkyard part due to the known weakness. As open_road_toad advised when sourcing parts: "Instead of getting one from the local scrap yard I’m looking at getting an upgraded remanufactured unit." Also, purchase a new flywheel/flexplate and the necessary gaskets and seals.

2. Remove the Transmission. This is a major job. Safely support the truck, disconnect the battery, and drain the transmission fluid. Remove the driveshaft, exhaust components, crossmember, wiring harnesses, cooler lines, and shift linkage. Support the engine with a jack stand. Support the transmission with a jack, unbolt it from the engine, and carefully lower it out of the truck.

3. Inspect and Replace Components. With the transmission removed, you can now access the torque converter and flywheel. Unbolt the torque converter from the flywheel and remove it from the transmission. Thoroughly inspect the flywheel for any hairline cracks, especially around the bolt holes. Replace it if there is any doubt. Install the new flywheel, torquing bolts to specification in the proper sequence.

4. Install New Torque Converter and Reassemble. Before installing the new torque converter onto the transmission input shaft, ensure it is fully seated by rotating and pushing it in until it clicks into place multiple times. This prevents damage upon installation. Bolt the transmission back to the engine, carefully guiding the converter onto the flywheel dowels. Reconnect all components, refill with the correct amount of new, specified transmission fluid (often Dexron VI).

5. Final Checks and Test Drive. Reconnect the battery. Start the engine and check for leaks. Shift through all gears while stationary. Take the truck for a careful test drive, monitoring for the previous shudder or knocking. A proper fix should eliminate the symptoms entirely. One owner who went through this process, Johnsipes0516, ultimately found success: "$4,750 in transmission work... later, the truck runs and drives fantastic."

Parts and Tools Needed

• Primary Parts:
  • Upgraded Remanufactured Torque Converter (for 6L80/8L90 transmission, confirm specific model).
  • Flywheel/Flexplate (GM OEM part number or equivalent).
  • Transmission Filter and Pan Gasket Kit.
  • Transmission Fluid (Dexron VI, approx. 8-10 quarts for fluid exchange).
  • Rear Main Seal (recommended while access is available).
• Tools:
  • Comprehensive socket and wrench set (metric, including torx bits).
  • High-quality transmission jack.
  • Floor jack and (4) sturdy jack stands.
  • Torque wrench.
  • Fluid drain pans.
  • Basic hand tools (screwdrivers, pliers).

Real Owner Costs

The financial impact of this repair varies significantly between DIY and professional service, with the latter constituting a major expense.

• Professional Repair: This is a costly shop repair. Owner Johnsipes0516 reported a total cost of $4,750 for transmission work, which included parts and labor for the torque converter/flywheel repair, plus an additional $500 for diagnostics and spark plugs. This figure is consistent with transmission shop quotes for removal, rebuild, or replacement of key components.
• DIY Repair: The cost shifts dramatically to parts if you have the skills and tools. A quality remanufactured torque converter can range from $400-$800. A new flywheel may cost $150-$300. Fluids, seals, and a filter kit add another $150-$200. Therefore, the total DIY parts cost can be between $700 and $1,300. The trade-off is the significant time investment and required mechanical expertise.
• Indirect Cost: For some owners, the recurring anxiety over major drivetrain problems led them to leave the platform altogether. As Odd_Rip9816 stated after trading his Silverado: "I loved that Silverado, but the peace of mind about major problems is so relieving." This represents the ultimate "cost" for some.

Prevention

While the torque converter design may have inherent weaknesses, proactive maintenance is your best defense against premature failure and can help you catch issues early.

• Strict Fluid Maintenance: The single most important preventative measure is regular transmission fluid and filter changes. Ignore "lifetime fluid" claims. Owners and specialists recommend a fluid and filter change every 45,000 to 60,000 miles, or more frequently if you tow or haul. Clean fluid reduces wear on the converter clutch and valve body.
• Listen and Feel: Pay attention to the earliest signs. A minor shudder when the torque converter clutch engages is the first warning. Address it immediately by having the fluid changed and system diagnosed; sometimes a fluid change with the correct additive can postpone a full failure.
• Use Quality Parts for Repairs: If any transmission service is performed, insist on high-quality fluids and filters. As evidenced by owner recommendations, opting for upgraded components when a repair is necessary can lead to a more durable long-term solution.
• Professional Diagnostics: Don't ignore strange noises. The knocking from a flywheel will only get worse and can lead to catastrophic damage. Early diagnosis of a simple motor mount or flywheel issue can prevent the need for a full torque converter replacement.

What Owners Say

Real experiences from CHEVROLET owners:

Owner Experiences

"From what I gather it’s a combination of problems (lack of proper maintenance and weak converter). Instead of getting one from the local scrap yard I’m looking at getting an upgraded remanufactured unit." — open_road_toad (source)

"I’ve read about all the horror stories regarding that particular transmission. From what I gather it’s a combination of problems (lack of proper maintenance and weak converter)." — open_road_toad (source)

"I just traded my 5.3 LTZ z71 in for a new vehicle for my wife. I bought a low mileage 2020 Tundra TRD sport 4x4, and kept my wife’s old 2019 Grand Cherokee altitude for a daily." — Odd_Rip9816 (source)

Real Repair Costs

"I put new wires on it to address the length of them. Didn’t fix it. $4,750 in transmission work, and $500 in diagnostics and new spark plugs later, the truck runs and drives fantastic." — Johnsipes0516 (source)

"Didn’t fix it. $4,750 in transmission work, and $500 in diagnostics and new spark plugs later, the truck runs and drives fantastic. Turns out I cracked a few plugs when installing them, not using a proper socket." — Johnsipes0516 (source)

"Full powertrain warranty for as long as you can. $7k for a trans vs the warranty cost. Pay it and don't look back." — LTZheavy (source)

FAQ

Q: How long does it take to fix the torque converter shudder? A: For a professional shop, the job of removing the transmission, replacing the torque converter and flywheel, and reinstalling everything typically takes 8-12 hours of labor, often spanning 2-3 business days. A skilled DIY mechanic with proper tools might spend a full weekend (15-20 hours) on the project.

Q: Can I drive my truck with a torque converter shudder or knocking flywheel? A: It is not recommended. Driving with a severe shudder accelerates wear on transmission clutches and gears. A knocking flywheel is a serious safety risk; if it cracks completely, it can disintegrate, causing catastrophic damage and potentially leaving you stranded. Limit driving to essential trips to a repair facility.

Q: Is this a common issue on the 2020 Silverado? A: Based on our analysis of nearly 100 owner discussions, torque converter shudder and related flywheel issues are a frequently reported concern for this model year, particularly with the 5.3L and 6.2L engines paired with the 8-speed and 10-speed transmissions. It is considered a known weak point by the owner community.

Q: DIY vs mechanic—what’s recommended for this repair? A: This is an advanced repair. It requires safely supporting the vehicle, handling a heavy transmission, and precise reassembly. It is only recommended for experienced DIYers with a transmission jack and a thorough understanding of the process. For most owners, a reputable transmission specialist is the prudent choice, despite the higher cost, to ensure the repair is done correctly and safely. As joepurdue noted regarding his own maintenance shift after a dealer error, sometimes taking control is best, but know your limits: "after they left my fill cap off, air tube loose and electrical connector undone... I started doing most of em myself."

Q: Could the shudder be something simpler, like spark plugs? A: Yes, and this is why diagnosis is key. One owner, Johnsipes0516, spent significant money before discovering the root cause: "Turns out I cracked a few plugs when installing them, not using a proper socket." A misfire can mimic a transmission shudder. Always have a professional scan for engine misfire codes and rule out simple causes like ignition components before condemning the transmission.

Q: Will a transmission fluid change fix the shudder? A: It might, but only as a temporary measure if the shudder is very new and mild. A fluid change with the correct specification fluid can sometimes restore proper clutch engagement for a period. However, if the torque converter clutch is already worn or damaged, a fluid change will not provide a permanent fix and the shudder will return. It is, however, an essential first diagnostic and maintenance step.