45,000 Miles In I Got Transmission Flush Done To My 2021 Silverado At Dealership, But After Spending $400 It's Worse Than Before

When you're investing thousands of dollars into a truck like the Chevrolet Silverado, you expect routine maintenance to help extend its life and improve performance. However, what happens when a maintenance job makes things worse? This is exactly the situation Joel Coeler, a member of the 2019–2025 Chevy Silverado & GMC Sierra Owners Facebook group, found himself in after a dealership service left his truck’s transmission in worse condition than before.

Joel posted:

"Truck is at 45k miles. 2021 5.3L with 8-speed. Got transmission ‘flush’ done at the dealership because I thought that was best to do at this mileage, along with tires. Honestly, it had kind of a slight clunk before but nothing out of the ordinary. But now it’s like missing shifts between first and second when accelerating, especially in turns—like pulling away from a stop. I am upset because I spent $400 for it to be worse than before. Any insight?"

Joel’s frustrating experience is just one example of the challenges Silverado owners often encounter when dealing with dealerships. Whether it’s a botched transmission flush, unfulfilled promises, or worse, some situations can escalate far beyond simple maintenance woes. For instance, one Silverado owner shared a shocking story about buying a new truck, only to have the bank demand $35,000 because their old truck's GMC dealer never paid it off—a nightmare scenario that highlights the importance of vigilance when navigating dealership transactions.

Similar Experiences with the 8-Speed Transmission

Will Crosby, another Silverado owner in the group, shared his own story, which sounds eerily familiar:

"My 2019 8-speed had similar issues at 50k miles and ended up needing a new transmission. Transmission fluid was replaced at 22k when they did a torque converter. Mine started acting up when it was cold, then got better, but it continued. After four days, I had it looked at."

Joel responded to Will, noting a possible connection between the colder weather and his truck’s shifting issues:

"Yeah, it also just dropped below freezing this last week here in Tennessee. So maybe that’s it."

Temperature can indeed play a role in how transmissions behave, especially when issues with fluid levels or viscosity are involved. However, cold weather alone shouldn’t cause these kinds of problems if everything is functioning as it should.

Advice from Fellow Silverado Owners

Another group member, Bmac Macuer, offered practical advice that may help Silverado owners troubleshoot similar issues:

"Check fluid level on idle when warm. Add 20 ounces of Lubegard Platinum."

While adding Lubegard or other transmission additives isn’t a factory recommendation, some owners have reported smoother shifting after using such products. If you’re experiencing transmission issues, it might be worth discussing this option with a trusted mechanic.

Why Transmission Flushes Can Cause Problems

Transmission flushes are often recommended by dealerships and service centers as part of regular maintenance, but they’re not always necessary—especially on modern vehicles. In some cases, flushing can loosen debris or contaminants that then circulate through the transmission, causing issues like the ones Joel described.

The Silverado’s 8-speed transmission, in particular, has been a point of contention for owners. Reports of clunking, shuddering, and missed shifts are not uncommon. It’s worth noting that Chevrolet issued a technical service bulletin (TSB) in 2019 for certain models with the 8-speed transmission, recommending a specific fluid exchange procedure to address torque converter shuddering. If your truck exhibits these symptoms, it’s important to check whether your vehicle is covered under a TSB or warranty program before paying out of pocket.

Useful Tips for Silverado Owners

If you’re a Chevrolet Silverado owner dealing with transmission issues—or want to avoid them—here are some tips to keep in mind:

1. Stick to Factory Recommendations:
   Before agreeing to a transmission flush, consult your owner’s manual. Chevrolet typically recommends a fluid exchange rather than a flush, especially for the 8-speed transmission.
2. Check Transmission Fluid Levels:
   As Bmac suggested, always check the fluid level when the vehicle is idling and warmed up. Low fluid can cause clunking or missed shifts.
3. Use High-Quality Additives Sparingly:
   Products like Lubegard Platinum can help improve shifting in some cases, but they should be used cautiously and as a supplement—not a replacement—for proper maintenance.
4. Monitor Cold Weather Performance:
   As Will and Joel discussed, colder temperatures can exacerbate transmission problems. If you notice worsening symptoms during the winter, have the system inspected for fluid viscosity or pressure issues.
5. Get a Second Opinion: Dealerships aren’t infallible. If you’re skeptical about the work performed—or the price tag—consult an independent transmission specialist for a second opinion. Sometimes, dealership services can feel more like a sales tactic than genuine care for your vehicle. One Silverado owner discovered this firsthand when the sales guy claimed his 2024 Silverado had been buffed and waxed, only to notice paint flaws the very next day—a clear example of why you need to double-check what you're paying for.
6. Stay Informed About TSBs and Recalls:
   Chevrolet has issued TSBs for known transmission issues in Silverado models with the 8-speed. Ensure your service provider is aware of these updates and check if your truck qualifies for repairs under warranty.
7. When to Consider Bigger Solutions: If persistent transmission issues or other major problems plague your Silverado, sometimes the best handling decision might not be a repair at all. For some owners, replacing the truck entirely can prove to be a smarter move. One 2024 Silverado owner found that losing $10K in a trade-in was better than dealing with endless repair headaches and declining resale value, underscoring the value of knowing when to cut your losses and move on.

Joel’s story highlights the frustration of spending money on maintenance only to face new problems. It’s a reminder to all Silverado owners to approach transmission servicing carefully—especially with the 8-speed. Unfortunately, stories like Joel's are not uncommon among Silverado owners. One owner even had to drive 594 miles back to the dealership to deal with issues on their brand-new 2024 Silverado—proving that these trucks sometimes carry unexpected headaches.

Have you faced similar transmission issues with your Silverado? Let us know in the comments below, and share any solutions that worked for you.

Armen Hareyan is the founder and the Editor in Chief of Torque News. He founded TorqueNews.com in 2010, which since then has been publishing expert news and analysis about the automotive industry. He can be reached at Torque News Twitter, Facebook, Linkedin, and Youtube. He has more than a decade of expertise in the automotive industry with a special interest in Tesla and electric vehicles.