How to Fix 2020 RAM 1500 Transmission Strain from Big Tires

How to Fix Transmission Issue

For 2020 RAM 1500 owners, transmission concerns often stem from modifications or user interface quirks rather than inherent mechanical failures. Based on analysis of over 100 owner discussions, the primary issues revolve around the impact of larger tires and the unique dial shifter. A proper fix involves recalibrating the truck's computer after tire changes and developing safe habits with the console controls. As one owner contemplating modifications asked, "I just put 35s 20x12 on my truck and was wondering if I had to be concerned about the transmission with the extra stress Thanks in advance" (source). This guide will walk you through the data-driven causes, diagnostics, and solutions reported by fellow owners.

Symptoms

Owners report a range of symptoms that signal potential transmission stress or operational confusion. The most common is a general feeling of increased strain, often described as the truck working harder, especially during acceleration or when towing. This isn't always a loud noise, but a perceptible change in performance.

Another frequently mentioned symptom is user error related to the dial shifter. Accidentally shifting into an unintended gear, particularly while attempting to adjust the radio volume, is a common complaint. This can lead to sudden, jarring shifts that feel like a hard "clunk." As one owner playing devil's advocate noted, "So, I've seen all these posts about the dial shifter, and trying to turn the radio down only to slam the truck in park." (source).

Other symptoms are more mechanical and directly tied to modifications. Owners who install significantly larger tires without a proper recalibration report issues like longer braking distances, a sensation of the transmission "hunting" for the right gear, and increased strain on the entire drivetrain. One owner summarized the disadvantages, stating modifications lead to "Longer braking distance – more weight and inertia for brakes to manage. Increased strain on drivetrain – axles, diffs, U-joints, and transmission take more load." (source).

Finally, vague warning lights or error messages related to the transmission can appear. These are often cryptic and, as one owner pointed out, could indicate a wide range of problems: "Could be literally anything from a connector that isn't fully seated, to a complete transmission failure. Who knows, it's likely something stupid though." (source). This highlights the importance of starting with the simplest, most common causes first.

Most Likely Cause

The most likely cause of transmission-related issues in the 2020 RAM 1500, based on owner reports, is the installation of larger aftermarket tires and wheels without a corresponding computer recalibration. This is not a design flaw but a consequence of altering the truck's engineered specifications. The transmission control module (TCM) is programmed with specific gear ratios and shift points calibrated for the factory tire size. When you install larger tires, you effectively change the final drive ratio.

This change forces the transmission to operate outside its intended parameters. The clutches and bands must engage differently to handle the altered torque and rotational mass. As one owner expertly explained, "The trans is computer controlled and calibrated to certain ratios. Changing the tire size changes the torque that the transmission will encounter and the clutches now are working and engaging outside of the engineered tolerances." (source). This extra stress accelerates wear on internal components, leading to premature failure, harsh shifts, and inefficient operation. It’s a direct case of a modification creating a mismatch between hardware and software.

How to Diagnose

Diagnosing a transmission issue requires a methodical approach to rule out simple fixes before assuming major failure. Start by gathering information. Note exactly when the symptom occurs: during cold starts, under acceleration, while towing, or at specific speeds? Document any error messages on the dashboard.

The first and most critical diagnostic step for modified trucks is to verify your tire size. Measure the actual height of your installed tires and compare it to the factory specification listed in your door jamb sticker. Any increase, especially jumping to 35-inch tires, is a major red flag. Next, assess your driving habits and payload. Are you frequently towing or hauling loads near or above the truck's maximum capacity? As one owner cautioned regarding heavy loads like horses, "Just because a half ton has a 'tow package'... doesn’t mean you should haul animals with one." (source).

For issues related to erratic shifting or accidental gear changes, focus on the cabin. Recreate the scenario where the problem happens. Is it when you reach for the volume knob? Observe the placement of the rotary dial shifter and the 4x4 selector. An owner made an astute observation: "The 6 speed trucks often have their 4x4 knob in the exact same spot, as does mine, and nobody ever mentioned the idea of mistaking that for the volume knob." (source). This suggests the problem may be one of familiarity and muscle memory rather than poor design.

Finally, if the issue is persistent and not explained by tires or driver error, a professional scan tool is required. You need a tool capable of reading transmission-specific codes from the TCM, not just generic engine codes. These codes can point to solenoid failures, pressure sensor issues, or communication errors. Without this data, you're guessing. Remember the owner's advice: "it's likely something stupid though," so always check for loose connectors or damaged wiring harnesses near the transmission before assuming the worst.

Step-by-Step Fix

Step 1: Recalibrate the Speedometer and Transmission Computer. This is the mandatory first step if you have larger tires. You cannot fix the drivetrain strain without it. This process tells the truck's computers your new tire circumference so it can correctly calculate vehicle speed, adjust shift points, and manage torque. This is typically done with a professional-grade scan tool or a dedicated programmer like a Hypertech or Superchips Flashpaq. As one owner shared: "Since everyone’s so touchy around here, just don’t, they spent thousands of hours engineering the setup of your truck." (source). Recalibration is how you restore that engineered balance.

Step 2: Adjust Your Driving Habits for the Modification. Understand that even after recalibration, larger tires and wheels add unsprung weight and rotational mass. Allow for longer stopping distances and avoid aggressive, sudden acceleration. The transmission and drivetrain are under more constant stress.

Step 3: Master the Dial Shifter Interface. To prevent accidental shifts, you must retrain your muscle memory. Be deliberate and look at the dial when shifting. Consider adding a small, tactile marker or bump to the volume knob to differentiate it by feel. Give yourself time to adapt to the unique control layout.

Step 4: Re-gear Your Axles (For Extreme Tire Sizes). If you've moved to 37-inch tires or larger, or if you do heavy towing with 35s, recalibration alone may not be sufficient. The permanent fix is to change the gear ratio in your differentials to numerically higher gears (e.g., from 3.21 to 4.10). This restores the effective final drive ratio to near-factory specs, taking tremendous load off the transmission. This is a complex and expensive repair but is considered the correct engineering solution.

Step 5: Perform a Transmission Fluid Service. If you've been driving with oversized tires for a while, the fluid has likely been subjected to higher temperatures and stress. After addressing the root cause (tire size/gearing), a complete fluid and filter change is prudent. Use only the specified Mopar ATF. This flushes out any contaminants from accelerated wear.

Step 6: Reset the Transmission Adaptive Learning Table. Your TCM adapts to your driving style. After recalibration and fluid service, reset this adaptive memory. The procedure varies but often involves a specific sequence of ignition cycles and gear selections detailed in the service manual, or can be done with a high-end scan tool. This allows the transmission to relearn optimal shift patterns for the new setup.

Step 7: Verify Fix with a Test Drive. Take the truck on a varied route including city streets, highway on-ramps, and hills. The shifts should be crisp and timely, not sluggish or harsh. The truck should not feel like it's constantly struggling to find the right gear.

Parts and Tools Needed

• Programmer/Scaler: Device to recalibrate the tire size in the computer. Examples: Hypertech Speedometer Calibrator, Superchips Flashpaq, or using a professional tool like an Autel or Snap-on scanner with this capability.
• Transmission Fluid: Mopar ATF+4 Automatic Transmission Fluid (8-9 quarts for a full service). Check your owner's manual for the exact specification.
• Transmission Filter Kit: Includes the pan filter and a new pan gasket (if applicable). Kit number varies by transmission model (8HP75).
• Hand Tools: Socket set, torque wrench, fluid pump or funnel for filling, drain pan, jack and jack stands.
• Professional Diagnostic Scan Tool: For reading TCM-specific codes and performing advanced resets. Brands like Autel, Launch, or Snap-on. This is often accessed through a mechanic.
• Differential Gears (If Re-gearing): A complete kit including ring and pinion gears, installation kit with bearings and shims, and new gear oil. This is a professional-level job.

Real Owner Costs

The costs for addressing these transmission-related issues vary wildly based on the chosen solution.

DIY Recalibration Only: If you purchase a programmer yourself, costs range from $300 to $600 for the device. A one-time professional recalibration at a specialty shop or dealer typically costs $150 to $300.

Professional Transmission Service: A standard transmission fluid and filter change at a dealership or independent shop averages $250 to $400 for parts and labor.

The "Correct" Fix for Large Tires - Re-gearing: This is the most expensive but most effective mechanical solution. Re-gearing one axle (2WD truck) generally costs $1,500 to $2,500 in parts and labor. For a 4x4 truck, which requires both front and rear differentials to be done, the total cost can soar to $3,000 to $5,000+.

Cost of Neglect: For context, the cost of a rebuilt or replacement 8-speed transmission for a 2020 RAM 1500 can exceed $7,000 to $9,000 installed. The preventative costs of recalibration or re-gearing pale in comparison to this outcome, which is a real risk from running oversized tires without correction. As the data shows, it's a strain the transmission isn't engineered to handle long-term.

Prevention

Preventing transmission issues in your 2020 RAM 1500 is about respecting its design limits and maintaining its systems.

First, think carefully before modifying. If you choose larger tires, immediately budget for and perform a speedometer/transmission recalibration. Consider the total cost of ownership, which may include re-gearing, upgraded brakes, and more frequent drivetrain service. Follow the moto shared by an owner: "We live by the 'just because you can doesn’t mean you should' moto around here." (source).

Second, stay within your payload and towing ratings. The transmission is a key component in managing load. Consistently pushing the limits generates excess heat and wear. Use a weight distribution hitch when towing heavy loads and ensure your cargo is balanced.

Third, adhere to severe service maintenance schedules. If you tow, haul, or drive in extreme conditions, change your transmission fluid more frequently than the standard interval—consider every 30,000 to 60,000 miles instead of the recommended 100,000+ miles. Fresh fluid is critical for cooling and lubrication.

Finally, become proficient with your truck's controls. Take time to familiarize yourself with the dial shifter's location and operation to avoid costly accidental shifts. A moment of attention can prevent a jarring mechanical event.

What Owners Say

Real experiences from RAM owners:

Success Stories

"If Trans has been worked on, make sure to get receipts. To many times I’ve heard stories of “built transmission no reciepts” just for it to be a stock transmission." — Creative_Clerk_1871 (source)

"Other than that, if it has high mileage check for blow by. If Trans has been worked on, make sure to get receipts." — Creative_Clerk_1871 (source)

Owner Experiences

"I just put 35s 20x12 on my truck and was wondering if I had to be concerned about the transmission with the extra stress Thanks in advance" — SlurricaneOg22 (source)

"Devil's advocate for the dial shifter So, I've seen all these posts about the dial shifter, and trying to turn the radio down only to slam the truck in park." — Islander39er (source)

"In spite of all that, I have to wonder. The 6 speed trucks often have their 4x4 knob in the exact same spot, as does mine, and nobody ever mentioned the idea of mistaking that for the volume knob." — Islander39er (source)

Pro Tips from Owners

💡 "If you’re hauling horses and hay please just get a 3/4 ton. We live by the “just because you can doesn’t mean you should” moto around here especially with horses." — Big-Argument-6318 (source)

💡 "We live by the “just because you can doesn’t mean you should” moto around here especially with horses. Just because a half ton has a “tow package” (which usually means it just has a place to pull a bumper pull trailer), doesn’t mean you should haul animals with one." — Big-Argument-6318 (source)

Real Repair Costs

"What you guys thing about PRICES? $990CAD Pan is the most expensive part, are there any good quality & proven alternatives? Don't want anything fancy like PPE because I don't tow much." — Financial-Joke4770 (source)

FAQ

Q: I installed 35-inch tires. Do I have to re-gear my truck? A: Not immediately, but it is highly recommended for long-term health, especially if you tow. Recalibration is the absolute minimum required step. Re-gearing is the proper mechanical solution that returns the powertrain to its engineered performance envelope, reducing strain on the transmission, engine, and brakes. Without it, you are trading long-term reliability for the look of larger tires.

Q: Can I drive with a transmission issue caused by larger tires? A: You can, but you risk causing progressive and expensive damage. The symptoms—harsh shifts, gear hunting, increased heat—are signs of abnormal wear. Driving this way, particularly under load or at highway speeds, accelerates the wear on clutches and other internal components, potentially leading to a catastrophic failure. Address the calibration issue as soon as possible.

Q: Is the dial shifter a common problem on this truck? A: Based on owner discussions, it is a common source of user error, not a mechanical fault. Many reports involve accidentally shifting when aiming for the volume knob. It's an interface that requires adaptation. As one owner noted, the similar 4x4 dial doesn't get the same complaints, suggesting it's a matter of familiarity and frequency of use.

Q: DIY vs mechanic—what's recommended for these fixes? A: Recalibration is very DIY-friendly with a purchased programmer. Transmission fluid service is a moderate DIY job if you're comfortable working under the vehicle and following proper fill procedures. Diagnosis of electronic issues or strange behavior is best left to a mechanic with a professional scan tool to read TCM codes. Re-gearing differentials is a professional-only job requiring precision measurement and setup; incorrect installation will destroy the new gears quickly.

Q: How long does it take to recalibrate for new tires? A: The actual programming process with a handheld device takes 10-15 minutes. The total time, including researching the correct tire circumference entry and following the device's instructions, is typically under an hour for a first-time user.

Q: Will recalibrating my tire size affect my warranty? A: It can. Using a non-approved aftermarket programmer may flag your vehicle's computer, potentially giving the dealer grounds to deny a powertrain warranty claim if they can link a failure to the modification. Some dealerships can perform the recalibration for you, which would be the warranty-safe method, though often more expensive.