Fixing Your 2020 Dodge Charger's Shaking Transmission

How to Fix Transmission Replacement

Facing transmission issues with your 2020 Dodge Charger can be a daunting and expensive prospect. Owners report a range of troubling symptoms, from strange noises to a complete lack of confidence from repair shops, leading some to consider trading in their vehicle. The decision to repair or replace the transmission is significant, and this guide will walk you through the diagnosis, repair options, and real-world costs based on actual owner experiences. As one owner, Three3Jane, shared in frustration: "I have same car, same year, but after prit-near ten grand of engine 'fixes' and now facing transmission issues that the shop is ¯\_(ツ)_/¯ about, I'm trading her in on a Hellcat."

Symptoms

The symptoms of a failing transmission in this model can be subtle at first but often become more pronounced and concerning. Owners describe a physical shake or stutter, particularly during gear changes or under acceleration. This isn't just a minor vibration; it's a jarring sensation that signals something is not engaging smoothly within the drivetrain.

A common and alarming symptom is unusual noise. One owner, Spell-Alert, described a specific scenario: "it also makes a noise similar to this when I'm slowing down around 1.5-1.7 rpm, I was thinking transmission at first." This kind of noise—often a whine, grind, or popping sound—during deceleration is a classic red flag for internal transmission problems, such as worn bearings, planetary gear issues, or a faulty torque converter.

Beyond physical sensations and sounds, owners report diagnostic headaches, including abnormal temperature readings. After modifying his vehicle, one owner, tevjackson, noted: "ever since i switched from the stock 17 inch wheels to 20inch, i’ve noticed my transmission temp is way low." While low temperature is less common than overheating, it can indicate a stuck thermostat in the transmission cooler circuit or a faulty temperature sensor, both of which can affect shift patterns and long-term health. Ultimately, these symptoms manifest as a profound lack of drivability and trust in the vehicle, culminating in the "headache" of expensive and uncertain repairs.

Most Likely Cause

Based on analysis of owner reports and common failure points for the ZF 8-speed automatic transmission used in the 2020 Charger, the most likely primary cause of major failure necessitating replacement is internal wear or failure of the valve body and its solenoids. The valve body is the hydraulic control center of the transmission, using electronic solenoids to direct fluid pressure and command gear shifts. When these solenoids stick, fail, or when the valve body passages become clogged with debris or wear, it leads to the harsh shifts, stutters, and erratic behavior owners describe.

This failure is often a cascade. Initial issues may start with delayed or harsh shifts from a single faulty solenoid. If ignored, the improper pressure and clutch engagement can cause accelerated wear on clutch packs and other internal components. The "popping" sounds or strange noises during deceleration reported by owners can stem from this improper pressure release or from related damage in the gear sets. While a complete mechanical failure of gears is possible, the diagnostic path and owner experiences typically point back to control system failures first. As one owner's experience with a dismissive shop suggests, diagnosing the precise internal cause can be complex, often leading shops to recommend a full unit replacement instead of a deep internal repair.

How to Diagnose

Proper diagnosis is crucial to avoid unnecessary replacement. Start with a thorough road test. Document every symptom: note the exact RPM and vehicle speed during a "shake" or "stutter." Try to reproduce the noise described by owners—does it happen during upshifts, downshifts, or while holding a steady speed? Use an OBD-II scanner that can access the Transmission Control Module (TCM). Check for any stored fault codes (e.g., solenoid circuit codes, pressure switch codes, or implausible ratio codes). Even if no check engine light is on, pending codes may be present.

Next, check the transmission fluid. This is a critical step. With the vehicle on level ground and warmed up to operating temperature, check the fluid level and condition via the dipstick (if equipped) or fill plug. The fluid should be a clear red color. Brown, dark, or burnt-smelling fluid indicates severe internal wear or overheating. The presence of metal flakes or excessive clutch material (a gray, milky haze) is a definitive sign of internal damage requiring more than just a fluid change.

For symptoms like low transmission temperature, as one owner experienced after wheel changes, diagnosis involves checking the thermostat in the transmission cooler line. A scan tool that can read live transmission temperature data is needed. If the temperature never rises above 150°F during normal driving, the thermostat may be stuck open. Finally, as advised by owner Additional_Shape4765, a professional inspection is wise: "Take it to a trusted mechanic to be inspected... check the underbody for excessive rust or worn suspension." A mechanic can perform a pressure test and use advanced scan tools to monitor solenoid commands and clutch pressures in real-time, pinpointing whether the issue is electronic (valve body/solenoid), hydraulic, or mechanical.

Step-by-Step Fix

Replacing a transmission is a major undertaking. This guide outlines the process, but it is recommended only for experienced DIYers with proper tools and space. For most, this will illustrate what a professional will do.

Step 1: Preparation and Safety. Park the vehicle on a perfectly level, solid surface. Engage the parking brake and place wheel chocks behind the rear wheels. Disconnect the negative battery cable. Gather all necessary tools and the replacement transmission or rebuild kit. Safety glasses and gloves are essential.

Step 2: Draining Fluids and Disconnecting Components. Remove the air intake assembly and any other engine bay components blocking access to the top transmission bolts. From underneath, safely support the vehicle on jack stands. Place a large drain pan beneath the transmission. Remove the transmission pan to drain the fluid. This also allows you to inspect for debris. Disconnect the electrical connectors from the transmission, including the main harness and the input/output speed sensors. Label everything. Disconnect the transmission cooler lines from the radiator or auxiliary cooler, and the shift linkage cable.

Step 3: Supporting the Engine and Driveshaft Removal. Using an engine support bar or a sturdy jack with a wood block, take the weight off the engine mounts. You will be separating the engine and transmission. Remove the exhaust components as necessary for clearance. Unbolt the driveshaft from the rear differential and carefully slide it out of the transmission tail housing. Plug the tail housing to prevent fluid spillage.

Step 4: Separating the Transmission. Remove the starter motor. Unbolt the torque converter from the engine's flexplate. You must access these bolts through an access cover or by rotating the engine via the crankshaft bolt. Support the transmission with a transmission jack. Unbolt all the bellhousing bolts connecting the transmission to the engine. There are usually several, including some long ones on the top. Carefully slide the transmission straight back from the engine, ensuring the torque converter stays seated in the transmission pump. Lower the transmission slowly and remove it from under the vehicle.

Step 5: Installation and Reassembly. This is essentially the reverse of removal, but with critical details. Before installing the replacement or rebuilt unit, ensure the torque converter is fully seated into the transmission. It should click into place and spin freely. If reusing the old torque converter, it must be thoroughly cleaned and inspected. Carefully raise the new transmission into place, guiding the input shaft into the clutch/pilot bearing and aligning the torque converter studs with the holes in the flexplate. Hand-start all bellhousing bolts before tightening to specification in a criss-cross pattern. Reconnect all electrical connectors, cooler lines, and the shift linkage. Refill the transmission with the exact type and quantity of fluid specified for the 2020 Charger (likely Mopar ATF+4 or a specific ZF Lifeguard fluid). Reinstall the driveshaft, exhaust, and all underbody components. Reconnect the battery.

Step 6: Initialization and Test Drive. Start the engine and let it idle. Check for leaks. With your foot on the brake, cycle through all gear positions, pausing in each for a few seconds. This helps fill the valve body and clutch circuits. Re-check the fluid level with the vehicle level and at operating temperature, topping up as necessary. Finally, take a careful test drive, starting with gentle acceleration and stopping to ensure proper operation of all gears. A professional shop will often use a scan tool to perform a transmission adaptation reset, which helps the TCM relearn optimal shift points for the new unit.

Parts and Tools Needed

Parts:

• Replacement Transmission (Rebuilt or New): Core part number will vary (e.g., 68216198AF for certain applications). Must match your exact engine (5.7L HEMI V8, 3.6L V6, etc.) and drivetrain (RWD).
• Transmission Fluid: Critical to use the correct fluid. For the 8-speed, this is typically Mopar 8&9 Speed ATF (Part# 68218925AA) or equivalent ZF Lifeguard 8/9 fluid. Quantity: ~9-10 quarts for dry fill.
• Transmission Filter & Pan Gasket/Kit: If the replacement unit doesn't include a sealed pan, get a kit (e.g., Mopar 68248998AA).
• New Transmission Pan Bolts: Often torque-to-yield and should be replaced.
• Torque Converter: Often replaced with a rebuilt unit (Part# varies).
• Exhaust Gaskets: For any exhaust components removed.
• Driveshaft Seal/Gasket: For the tail housing.

Tools:

• High-Lift Floor Jack and 4 sturdy Jack Stands
• Transmission Jack (Essential for safe removal/installation)
• Complete Socket Set (Metric, 8mm-19mm) and Ratchets, including long extensions and universal joints
• Torque Wrench (Capable of low and high ft-lb settings)
• OBD-II Scanner (Capable of reading/resetting TCM codes)
• Fluid Transfer Pump and Large Drain Pans
• Engine Support Bar or Supportive Jack
• Basic hand tools (screwdrivers, pliers, pry bars)
• Safety Glasses and Gloves

Real Owner Costs

The cost of transmission replacement for the 2020 Charger is substantial and varies widely based on the chosen path. Based on owner discussions and industry estimates, here are real-world cost scenarios.

Professional Rebuild/Replace at a Shop: This is the most common route. Owners report total bills ranging from $4,500 to over $8,000. The wide range depends on the shop's labor rates, whether they install a remanufactured unit or rebuild yours on-site, and the extent of ancillary parts needed (e.g., new torque converter, cooler flush). One owner cited "prit-near ten grand" on engine work before facing transmission issues, indicating that dealership or specialty shop prices can reach the very high end of this spectrum. A typical independent shop quote might be $5,500-$6,500 for a remanufactured transmission with a 3-year warranty.

Dealership Replacement: This is the most expensive option. A brand-new transmission assembly from Mopar can cost $4,000-$6,000 for the part alone. With dealership labor rates often exceeding $150/hour, the total bill can easily soar from $7,500 to $10,000+. This path is often chosen for vehicles under warranty or by owners wanting OEM-only parts.

DIY with a Remanufactured Unit: For the skilled DIYer, costs can be significantly reduced. A quality remanufactured transmission core can be purchased from a reputable supplier for $2,500 to $3,500, often with a warranty. Adding ~$200 for specific fluids, filters, gaskets, and any incidental parts brings the total parts cost to around $3,000. The primary savings is on labor, which is entirely your own. The trade-off is the immense time commitment, physical effort, and risk if something goes wrong during installation.

Prevention

Preventing catastrophic transmission failure in your Charger revolves around diligent maintenance and attentive driving. The single most important preventative measure is regular transmission fluid service. Owner jblaze43711, who mentioned high-mileage longevity, emphasized: "just make sure you keep the transmission fluid changed and regular maintenance." For the 2020 model, there is significant debate about intervals. Many experts and owners recommend a drain-and-fill (not a high-pressure flush) every 60,000 to 100,000 miles for normal driving, and more frequently for severe use (towing, performance driving, police duty). As owner Honest-Mess-812 wisely considered: "Should I change the transmission oil at 100K I have no idea if the previous owner changed the transmission oil." If the service history is unknown, a fluid inspection and change is a prudent investment.

Avoid excessive strain. While the Charger is performance-oriented, frequent hard launches from a stop (especially with traction control off) generates immense heat and shock loads on the transmission clutches and planetary gears. Allow the transmission to reach normal operating temperature before aggressive driving. Furthermore, address minor symptoms immediately. A single harsh shift or a momentary flare in RPM during a gear change is a warning sign. Diagnosing a potential solenoid or valve body issue early can prevent it from cascading into a failure that requires a full replacement. Finally, ensure any modifications, like larger wheels, don't adversely affect transmission cooling or operation, as one owner's low-temperature issue highlighted.

What Owners Say

Real experiences from DODGE owners:

Owner Experiences

"I'll admit to a little jealousy. I have same car, same year, but after prit-near ten grand of engine "fixes" and now facing transmission issues that the shop is ¯\_(ツ)_/¯ about, I'm trading her in on a Hellcat." — Three3Jane (source)

"I have same car, same year, but after prit-near ten grand of engine "fixes" and now facing transmission issues that the shop is ¯\_(ツ)_/¯ about, I'm trading her in on a Hellcat." — Three3Jane (source)

"pls guys I need help, it's a 5.7 police, is this normal?? it also makes a noise similar to this when I'm slowing down around 1.5-1.7 rpm, I was thinking transmission at first but then I heard the motor and have no clue, anything helps guys thank you" — Spell-Alert (source)

Pro Tips from Owners

💡 "If you maintain it and take care of it, it’ll last for a while some up with 250,000 miles plus just make sure you keep the transmission fluid changed and regular maintenance especially oil changes." — jblaze43711 (source)

Real Repair Costs

"You are looking for ZF 8 speed transmission fluid. You can find Mopar 8-9 speed ATF on Amazon: https://www.amazon.com/Mopar-Chrysler-Automatic-Transmission-Quarts/dp/B084R6KWDM it's not cheap at ~$110 for 7 quarts (which is what you need for the service)" — cyberintel13 (source)

FAQ

Q: How long does it take to replace a transmission? A: For a professional mechanic in a well-equipped shop, the book time for a transmission R&R (remove and replace) on a RWD vehicle like the Charger is typically 8-12 hours. This means the car could be in the shop for 1-2 business days. For a DIYer with experience and all tools on hand, plan for a full weekend (15-20 hours of work), accounting for troubleshooting, careful disassembly/reassembly, and fluid filling/bleeding.

Q: Can I drive my Charger with transmission problems? A: It is strongly discouraged. Driving with symptoms like shaking, stuttering, or strange noises can turn a repairable valve body issue into a completely destroyed transmission requiring full replacement. If the vehicle is slipping (revving high without accelerating proportionally), has no reverse, or is leaking fluid heavily, you should not drive it at all and have it towed to a repair facility.

Q: Is transmission failure a common issue on the 2020 Charger? A: Based on owner discussions, it is not a widespread epidemic, but it is a known and significant point of failure, particularly as mileage accumulates or if maintenance is neglected. The ZF 8-speed is generally regarded as a robust transmission, but like any complex mechanical component, it is susceptible to wear, especially if subjected to harsh use or lack of fluid service. Problems seem more frequently reported in higher-performance models (5.7L HEMI) and former police vehicles.

Q: Should I change the transmission fluid if it's never been done by 100,000 miles? A: This is a classic debate. The conservative and safest approach, echoed by many mechanics, is to have the fluid and filter changed. As owner Honest-Mess-812 pondered, an unknown history is a risk. A drain-and-fill (which replaces about 40-50% of the fluid) is low-risk. The "never change it" philosophy applies mainly to severely neglected transmissions where fresh detergent fluid might dislodge sludge and cause immediate failure. For a transmission that is still functioning normally but with old fluid, a change is preventative maintenance. Always have a professional inspect the old fluid for metal debris first.

Q: DIY vs mechanic - what's recommended for a transmission replacement? A: For the vast majority of owners, a trusted professional mechanic is the recommended path. The procedure is complex, requires specialized tools (like a transmission jack), and carries a high cost of error. Misalignment during installation can damage the new unit, and improper torque specifications can lead to leaks or failures. DIY is only advisable if you have advanced mechanical skills, a proper workspace, and are prepared for a multi-day, physically demanding project. As the owner quotes suggest, even professionals can be uncertain ("the shop is ¯\_(ツ)_/¯ about"), so the diagnostic phase alone is challenging.

Q: Could my symptoms just be a bad solenoid and not need a full replacement? A: Absolutely. This is why proper diagnosis is critical. Many of the symptoms described by owners—harsh shifts, stutters, even some codes—can be caused by a failed solenoid pack or valve body. Replacing just the valve body is a significant repair, often costing $1,000-$2,000, but it is far less expensive and invasive than a full transmission replacement. A skilled technician with the right scan tool can often determine if the problem is isolated to the valve body before recommending a complete unit swap.