P0733 on 2019-2023 Ram 3500: Gear 3 Incorrect Ratio Causes and Fixes

What's Unique About the 2019-2023 Ram 3500

This generation of Ram 3500 can be equipped with three distinct heavy-duty transmissions: the Chrysler-built 68RFE (standard on most models), the Aisin AS69RC (optional on high-output Cummins models), or the ZF-based 8-speed 8HP75-LCV (with the 6.4L Hemi). For the 68RFE and 8-speeds, P0733 is a known issue often addressed by Technical Service Bulletins (TSBs) for software glitches. TSB #21-016-20 specifically calls out a software fix for P0733. Unlike many vehicles where this code points directly to a major mechanical failure, on these Rams, the cause is frequently a software calibration issue that causes the code to be set incorrectly. This makes a dealer visit for a potential software update using a wiTECH scan tool a highly probable fix. For the Aisin, while robust, it is known for having a locked TCM, making software tuning nearly impossible and shifting the diagnostic focus more toward fluid condition or mechanical issues.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light (Malfunction Indicator Lamp) is on
🎬 Watch: Learn more about what causes the P0733 error code
• "Service Transmission" message on the dash
• Harsh, jerky, or delayed shifting, especially into 3rd gear
• Transmission slipping or engine RPMs flaring (revving up) between shifts
• Vehicle gets stuck in one gear (limp mode), often 3rd gear
• Clunking noises during or between shifts
• Reduced fuel efficiency
• Inability to shift into a forward or reverse gear after entering limp mode and shifting to Park

Most Likely Causes

1. Low or Dirty Transmission Fluid 🔴 High Probability Heavy-duty use accelerates fluid breakdown. These transmissions are 'sealed' and lack a traditional dipstick, making it difficult for owners to check the level and condition, increasing the chance of running low or with degraded fluid without realizing it.
   How to confirm: A technician must check the fluid level and condition following a specific procedure at a certain temperature (often 86°F-122°F). For the 68RFE, use Mopar ATF+4. For the Aisin AS69RC, use Mopar ASRC fluid (JWS 3309 spec). For the 8-speed ZF, use Mopar ZF 8&9 Speed ATF. The fluid should be at the correct level and not excessively dark or smell burnt. Note: TSB S2621000003 mentions that 8-speed fluid can have a naturally burnt smell, so smell is not a definitive indicator of failure.
   Typical fix: Perform a transmission fluid and filter change using the correct Mopar-specified fluid for your specific transmission (68RFE, Aisin, or 8-speed).
   Est. part cost: $150-$300
2. Transmission Control Module (TCM) Software Update Needed 🔴 High Probability Multiple TSBs have been issued by Ram for this generation to address software issues that can cause false or premature P0733 codes and other shifting problems. TSB #21-016-20 is a prime example for P0733 specifically.
   How to confirm: A dealership or a qualified shop with a wiTECH scan tool can check the current software calibration ID (CalID) of the TCM and compare it against the latest available updates from Ram.
   Typical fix: Reprogramming (flashing) the TCM with the latest software version. This is a non-mechanical repair that can often be done in under an hour.
   Est. part cost: $0-$250 (Labor cost at a dealership)
3. Faulty Valve Body or Shift Solenoid 🟡 Medium Probability The solenoid pack (a block of electro-mechanical valves) is a common failure point on the 68RFE transmission. Debris in the fluid can cause solenoids to stick or the valve body passages to become blocked, preventing correct hydraulic pressure for the 3rd gear clutch application. For 2019+ 68RFE models, the valve body and solenoid pack were updated. 🎬 See this walkthrough of a 68RFE valve body installation
   How to confirm: A technician can test the solenoids' resistance and command them with a scan tool. In a real-world forum example, a dealer diagnosed a faulty valve body as the initial step before finding more severe damage. Inspection of the pan for excessive metal debris is required.
   Typical fix: Replace the faulty shift solenoid pack or the entire valve body assembly. This is located inside the transmission oil pan and can be done without removing the transmission.
   Est. part cost: $400-$1400 for a valve body, plus labor.
4. Internal Transmission Failure ⚪ Low Probability While less common on newer vehicles, heavy towing or high mileage can lead to wear of internal components. On the 8HP75 transmission, a known failure point is the 'D' clutch pack. On the 68RFE, the overdrive clutches are a known weak point, though P0733 points specifically to the 3rd gear clutch set.
   How to confirm: This is a diagnosis of last resort. It is confirmed when a technician drops the transmission pan and finds significant metallic debris or clutch material. In one owner's experience on the HD Rams Forum, the dealer was required by Ram to drop the pan and take pictures after a valve body diagnosis, which then revealed metal and led to a full transmission replacement under warranty.
   Typical fix: Rebuilding or replacing the entire transmission assembly. This is a major repair.
   Est. part cost: $3000-$8000+

Rare But Worth Checking

• Faulty Transmission Speed Sensor: A failing input or output speed sensor can send incorrect data to the TCM, causing it to think there's a ratio error when there isn't. This will usually be accompanied by other speed sensor-specific codes (e.g., P0722).
• Damaged Wiring or Connectors: Corrosion or damage to the wiring harness leading to the transmission can interrupt signals from sensors or to solenoids, triggering the code. This can also affect the main CAN bus terminals inside the valve body itself, leading to communication loss codes like U0101.

Diagnosis Steps

1. Check the transmission fluid level and condition. This is the most crucial first step. As these are sealed units, this must be done by a technician at a specific fluid temperature. If low, top off and check for leaks. If dark or full of debris, a fluid/filter change is needed.
2. Scan for other trouble codes. Additional codes for specific solenoids (e.g., P0796), sensors (e.g., P0722), or communication (e.g., U0101) can help pinpoint the problem.
3. Check for Technical Service Bulletins (TSBs). Use the vehicle's VIN to see if any TSBs apply. Specifically check for TSB #21-016-20 for a P0733 software fix and TSB S2621000003 for general 8-speed diagnostic guidance.
4. If fluid is good and no TSBs apply, perform a road test to confirm the symptoms. Note when the slipping or harsh shifting occurs.
5. Test the shift solenoids and valve body. A qualified technician can command the solenoids on and off with a wiTECH scan tool. They may also check line pressure.
6. Inspect wiring and connectors for any visible damage, corrosion, or loose connections between the TCM and the transmission.
7. If all other tests pass, drop the transmission pan to inspect for metal shavings or clutch material. Finding significant debris confirms an internal mechanical failure, which may require transmission removal and inspection.

Parts You'll Likely Need

• Transmission Fluid and Filter Kit (OEM #Varies by transmission. Aisin: Mopar ASRC Fluid (P/N: 5189977AE for gallon). 68RFE: Mopar ATF+4. 8-Speed: Mopar ZF 8&9 Speed ATF.) — This is the most common and fundamental fix. Low or degraded fluid is a primary cause of slipping and incorrect ratio codes.

Related Codes That Often Appear With This One

• P0731 — Incorrect Ratio in 1st Gear. Often set together due to a shared underlying cause like a software glitch or widespread fluid problem.
• P0732 — Incorrect Ratio in 2nd Gear. Similar to P0731, indicates a broader transmission control issue rather than an isolated gear problem.
• P0734 — Incorrect Ratio in 4th Gear. Seeing multiple incorrect ratio codes strongly points towards a systemic issue like low fluid, a failing TCM, or a major internal problem.
• P0868 — Transmission Fluid Pressure Low. This code often accompanies ratio errors because low hydraulic pressure is a primary cause of clutch slippage.
• U0101 — Lost Communication With TCM. This can occur if wiring is damaged or if corrosion develops in the valve body connectors, pointing to an electrical rather than purely mechanical issue.

Technical Service Bulletins (TSBs) & Recalls

• 21-016-20
• S2621000003 REV.A

Platform-Specific Known Issues

• TSB #21-016-20 notes that customers may experience a MIL illumination with DTC P0733-00 and that a software enhancement is available to correct harsh garage shifts and the code. [Bulletin #21-016-20]
• TSB #S2621000003 REV.A lists P0733 as a potential diagnostic code for a wide range of 8-speed transmissions (8HP75, etc.) and advises that fluid smell alone is not an indicator of failure and that valve body replacement should be considered before transmission replacement.
• Owner Experience (8HP75-LCV): An owner on 'hdrams.com' with a 6.4L Hemi and 8-speed transmission reported a P0733 code at 26,000 miles. The dealer initially diagnosed a faulty valve body, but upon dropping the pan as required by Ram, found metal shavings. This led to a full warranty replacement of the transmission, cooler, and lines.
• Owner Experience (8-Speed): An owner on 'ramforum.com' with a 2019 2500 6.4L Hemi experienced P0733 at 32,000 miles. The dealer noted the fluid was not burnt and proceeded directly to a full transmission replacement under warranty, which resolved the issue.

Mechanic-Grade Diagnostic Values

• 68RFE Shift Solenoid Resistance (UD, OD, 4C, 2C, MS) — expected: ~1.3 Ohms. Failure: An open circuit (infinite resistance) or a reading significantly different from 1.3 Ohms.
• 68RFE Pressure Control Solenoid Resistance — expected: ~4.9 Ohms. Failure: An open circuit or a reading significantly different from 4.9 Ohms.
• 68RFE Clutch Volume Index (CVI) - L/R Clutch — expected: 45-134. Failure: A value outside this range indicates excessive wear or a hydraulic leak in the clutch circuit.
• 68RFE Clutch Volume Index (CVI) - 2C Clutch — expected: 25-85. Failure: A value outside this range indicates excessive wear or a hydraulic leak in the clutch circuit.
• 68RFE Clutch Volume Index (CVI) - OD Clutch (Used for 3rd gear) — expected: 30-100. Failure: A value outside this range is a strong indicator for the cause of P0733, pointing to wear on the Overdrive clutch pack.

Hidden / Shadow Codes Worth Checking

• P1DA8-00: Incorrect Gear Ratio Clutch A, B or D Defective. This manufacturer-specific code often accompanies P0733 on 8-speed transmissions and points directly to an internal clutch failure. (see via Dealer-level scan tools like wiTECH or advanced aftermarket scanners (e.g., AlfaOBD).)
• P1D92-00: Incorrect Gear Ratio - Clutch 4 Defective. Similar to P1DA8, this code further confirms the fault lies within the transmission's internal clutch assemblies on 8-speed models. (see via Dealer-level scan tools like wiTECH or advanced aftermarket scanners.)

Scan Tool Commands That Help

• wiTECH, Autel, AlfaOBD: Quick Learn — This procedure must be performed after replacing the transmission, valve body, solenoid pack, or after a battery disconnect to reset all adaptive values to factory presets and allow the TCM to relearn clutch fill volumes and shift timing. Failure to do so can result in poor shift quality or premature component failure.
• wiTECH, AlfaOBD: View Clutch Volume Index (CVI) — Used to diagnose internal wear. CVI values represent the volume of fluid needed to apply a clutch. Values that are out of specification are a strong indicator of worn clutch packs or leaking seals, helping to confirm an internal mechanical failure without disassembly.
• wiTECH, AlfaOBD: Reset Adaptive Values — A function within the Quick Learn procedure that clears the TCM's learned shift adaptations. This forces the TCM to start a new learning process based on the current mechanical state of the transmission.

Wiring & Ground Locations

• TCM Power Fuses — Under-hood fuse box, located on the driver's side of the engine bay.. Loss of power to the TCM can cause a host of transmission codes, including ratio errors. Check fuses F21, F22, F33, F57, and F72.
• Main Chassis Ground — On the body sheet metal near the driver's side battery and headlight assembly.. A corroded or loose main ground can cause intermittent communication and power issues for the TCM, leading to erratic behavior and fault codes.
• TCM Ground Pins — At the TCM connector. For some models, the TCM is integrated into the PCM/ECM.. A forum user identified specific ground pins (37, 39, 51, 57) at the TCM connector. A poor ground on any of these can cause internal logic errors and incorrect sensor readings, potentially triggering a P0733.
• 68RFE Main Connector — On the driver's side of the transmission case.. This is the single point of electrical connection for all solenoids and sensors inside the transmission. Corrosion or backed-out pins in this connector can interrupt the signal for the solenoids controlling 3rd gear, directly causing a P0733.

Real Owner Repair Stories

• Ram Heavy Duty Forum user 'JimKIII' (2022 Ram 3500 w/ 6.4L Hemi and 8HP75-LCV transmission, 26,000 miles) — Check Engine Light with code P0733 and 'Service Transmission' message on the dash.
  ❌ Tried (didn't work) The initial diagnosis from the dealer was a faulty valve body.
  ✅ What actually fixed it Before replacing the valve body, Ram required the dealer to drop the transmission pan and inspect for debris. The technician found metal shavings in the pan, which changed the diagnosis to an internal failure. Ram approved a complete transmission replacement under warranty, which resolved the issue.
• 5thGenRams Forum user 'Phantom_h60' (2020 Ram 1500 (similar 8-speed transmission logic)) — P0733 - Gear 3 Incorrect Ratio.
  ❌ Tried (didn't work) A valve body had already been replaced for the same issue at 9,000 miles, but the problem returned.
  ✅ What actually fixed it Because the valve body replacement had already failed to fix the issue, Ram authorized a new transmission replacement under warranty.

"I Checked Everything" — The Actual Cause

• The diagnostic equivalent for a transmission code is finding the fluid level is full and the condition is clean, yet the problem persists. For the Ram HD, this scenario is common. A technician may check the fluid and find no issue, leading them to suspect a software or solenoid problem. However, as seen in a real-world repair story, the actual cause was significant metal debris in the bottom of the pan, indicating a severe internal failure that was only discovered after the pan was dropped for inspection. This confirms that a clean dipstick (or in this case, a clean fluid sample from the check plug) does not rule out a major mechanical failure.

When the Usual Fixes Don't Work

• While the provided TSB #21-016-20 points to a software fix for P0733, a detailed owner story from the HD Rams Forum for a 2022 Ram 3500 with the 8-speed transmission shows a different outcome. The dealer's first step was to diagnose a faulty valve body. However, per manufacturer instruction, they dropped the pan before proceeding and found metal shavings. This immediately escalated the repair to a full transmission replacement under warranty, bypassing both software flashes and valve body swaps as the final solution. This demonstrates that while software and valve bodies are common culprits, they can also be incorrect initial diagnoses for a deeper mechanical failure.

OEM Part Supersession History

• Various (White/Grey Connector Solenoid Packs used pre-2019) → 68456067AA (Blue Connector) — For the 2019 model year, the 68RFE was updated with a new valve body and solenoid pack to improve TCC control and address other complaints. The new solenoid has different internal functions.
  Heads up: The 2019+ blue connector solenoid pack (68456067AA) is NOT interchangeable with the earlier white or grey connector packs. Using the wrong pack will result in improper function and fault codes.

Model Year Variations Within This Range

• 2019-2023 (68RFE only): Starting in 2019, the 68RFE transmission received significant hydraulic control changes. This included a new valve body with an added lower section, a redesigned solenoid pack (changing from a grey to a blue connector), and pump modifications. These changes altered how the torque converter clutch and reverse clutch are controlled. This is critical for diagnosis, as parts like the solenoid pack are not backward compatible with pre-2019 models.