P0733 on 2019-2023 Ram 2500: Gear 3 Incorrect Ratio Causes and Fixes

What's Unique About the 2019-2023 Ram 2500

For this generation of Ram 2500, the cause of P0733 can differ based on the powertrain. Models with the 6.4L Hemi use a ZF 8-speed transmission (8HP75-LCV), where P0733 can be a software glitch fixed by TSB 21-016-20. However, owner forums document a common diagnostic progression: if the software update doesn't work, a faulty valve body is suspected. If the dealer then finds metal debris in the pan, a full transmission replacement is authorized under warranty. For trucks with the 6.7L Cummins Turbo Diesel and Aisin AS69RC transmission, P0733 is also a known issue, though less common, and historically pointed towards internal failures requiring replacement per older TSBs.

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 (MIL) is on
• "Service Transmission" message on the dash
• Harsh or clunky shifting, especially on the 2-3 upshift
• Transmission slipping (engine RPMs flare up without an increase in speed)
• Vehicle gets stuck in one gear (limp mode), often after a harsh shift event
• Delayed or no engagement when shifting into Drive or Reverse
• Symptom disappears after restarting the truck, but the code remains stored

Most Likely Causes

1. Transmission Control Module (TCM) Software Issue 🔴 High Probability → Shop Transmission Assembly Manufacturer TSB #21-016-20 specifically identifies a software issue that can cause P0733 and recommends a software update as the fix for harsh shifting on the 8HP75 transmission.
   How to confirm: A Ram dealership can check the vehicle's VIN against TSB #21-016-20 and verify the current software calibration using a wiTECH scan tool.
   Typical fix: Update the TCM software to the latest version. This must be done by a dealership or a qualified shop with the appropriate tools.
   Est. part cost: $0 (if under warranty) - $200
2. Low or Dirty Transmission Fluid 🟡 Medium Probability → Shop Transmission Assembly These transmissions have no dipstick, making fluid level checks non-trivial for a DIYer. 🎬 Watch: How to check fluid levels without a dipstick. Low fluid causes a drop in hydraulic pressure, leading to slipping.
   How to confirm: The fluid level must be checked by a technician using the fill plug while the vehicle is level and the transmission fluid is at a specific temperature, typically between 86°F and 122°F (30°C-50°C). The fluid condition (color, smell, debris) should also be inspected.
   Typical fix: Perform a transmission service, which involves correcting the fluid level and/or replacing the fluid and filter pan. 🎬 See this walkthrough of a complete 8-speed transmission service. Use only the manufacturer-specified ATF (Mopar ZF 8&9 Speed ATF, Part# 68218925AB).
   Est. part cost: $150-$350
3. Faulty Valve Body 🟡 Medium Probability → Shop Transmission Valve Body Forum discussions from owners of this specific vehicle show that a faulty valve body is a common diagnosis from dealers when this code appears after software and fluid have been ruled out. It is often the next step in the diagnostic process before checking for internal damage.
   How to confirm: This is diagnosed by a professional after ruling out fluid and software issues. It may involve pressure testing specific hydraulic circuits or may be replaced as a diagnostic step by the dealer.
   Typical fix: Replacement of the transmission valve body. 🎬 Watch: How to install a new valve body on this truck.
   Est. part cost: $800-$1500
4. Internal Mechanical Failure ⚪ Low Probability While less common, multiple owner reports confirm that finding metal debris in the transmission pan after a P0733 code has led to a full transmission replacement under warranty. This is often the final diagnosis after a valve body replacement is considered or attempted.
   How to confirm: Dropping the transmission pan and inspecting for excessive metal shavings or clutch material on the magnet. This is a definitive sign of internal failure.
   Typical fix: Complete transmission replacement or overhaul.
   Est. part cost: $5000-$9000

Rare But Worth Checking

• Faulty Shift Solenoid: → Shop Transmission Valve Body While a single solenoid can fail, it is often diagnosed and replaced as part of the entire valve body assembly on these modern transmissions.
• Faulty Input/Output Speed Sensor: A failing speed sensor can send incorrect data to the TCM, but this will typically be accompanied by other sensor-specific fault codes.

Diagnosis Steps

1. Scan the TCM for any and all stored trouble codes. Note if P0733 is the only code or if others are present.
2. Check with a Ram dealer if Technical Service Bulletin #21-016-20 or #S2621000003 REV.A applies to the vehicle's VIN. If so, follow the TSB's recommendation for a software update.
3. If no TSB applies, have a qualified technician check the transmission fluid level and condition. This must be done on a level surface with the fluid temperature between 86°F and 122°F (30°C-50°C).
4. If the fluid is low, top it off with Mopar ZF 8&9 Speed ATF (Part# 68218925AB), clear codes, and test drive. If the fluid is dirty or burnt, a fluid and filter change is recommended.
5. If the code persists, the next likely step is dealer diagnosis of the valve body. This may involve pressure tests or replacement based on symptoms.
6. As a final confirmation, the dealer may be required by the manufacturer to drop the transmission pan to inspect for metal debris before authorizing a major repair.
7. If significant metal shavings are found, this confirms a severe internal failure requiring a complete transmission rebuild or replacement.

Parts You'll Likely Need

• Transmission Fluid and Filter Kit (OEM #68218925AB (Fluid, per quart)) — Low or dirty fluid is a common cause of transmission slipping and ratio codes. A fluid and filter service is a primary diagnostic and maintenance step.
  Trusted brands: Mopar, ZF
  OEM price range: $250-$400
  Aftermarket price range: $150-$250
• Transmission Valve Body (OEM #68563806AB, RL402284AA (Varies by VIN and build date)) — This is a frequently diagnosed failure point on this platform for P0733 after software and fluid issues are ruled out, as documented in owner forums.
  Trusted brands: Mopar
  OEM price range: $1000-$1800
• Complete Transmission Assembly — In cases where metal is found in the pan, a full replacement is often the required repair, especially when performed under the vehicle's powertrain warranty.
  Trusted brands: Mopar
  OEM price range: $6000-$9000

Related Codes That Often Appear With This One

• P0700 — P0700 is a generic code indicating that the Transmission Control Module (TCM) has stored a fault. It often appears alongside specific transmission codes like P0733 to signal the driver that a transmission-specific issue exists.

Technical Service Bulletins (TSBs) & Recalls

• S2621000003 REV.A: Lists P0733 among other codes for various 8-speed transmissions (including 8HP75), indicating a known pattern of issues.
• 21-016-20: Specifically identifies P0733-00 (Gear 3 Shift Incorrect Ratio) on the 8HP75 and points to a software enhancement as the remedy for it and associated harsh shifts.
• 21-030-17: Applies to older (2016-2017) Cummins-equipped trucks with the Aisin AS69RC transmission, but shows P0733 as a known code indicating a failure that required full transmission replacement.

Platform-Specific Known Issues

• A software glitch is a known cause for this code on 6.4L Hemi models, addressed by TSB #21-016-20, which calls for a TCM software update.
• Multiple owner reports on forums for Ram Heavy Duty trucks confirm that P0733 can be an early indicator of a serious failure requiring valve body or full transmission replacement, often performed under the vehicle's powertrain warranty.
• The diagnostic path for the dealer often follows: 1) Check for TSB/software update. 2) Propose valve body replacement. 3) Get authorization to drop pan, find metal. 4) Get authorization for full transmission replacement.

Mechanic-Grade Diagnostic Values

• Transmission Solenoid Coil Resistance — expected: 5 to 15 Ohms (general specification). Failure: An open circuit (infinite resistance) or a shorted circuit (near zero resistance) indicates a failed solenoid coil.
• Clutch Volume Index (CVI) — expected: Varies by clutch pack and transmission type (e.g., 20 to 77 for 1-2 shift on some models).. Failure: A CVI value that is out of the specified range for a particular clutch indicates excessive wear or a hydraulic leak in that circuit.
• Transmission Fluid Temperature for 'Quick Learn' Procedure — expected: Above 60°C (140°F) or between 50°C (122°F) and 100°C (212°F) depending on procedure.. Failure: Attempting the procedure outside the specified temperature range may cause it to fail or not complete successfully.

Scan Tool Commands That Help

• wiTECH or AlfaOBD: Quick Learn — This procedure must be performed after replacing the transmission, valve body/TCM, or when adaptation memory cells have been cleared. It resets and relearns the clutch application points and shift timing.
• wiTECH: Reset Adaptive Values — Used before performing a 'Quick Learn' to clear out old clutch wear data from the TCM's memory.
• wiTECH: View Clutch Volume Index (CVI) Data — To diagnose internal wear or hydraulic leaks. The TCM calculates the volume of fluid needed to apply each clutch pack; out-of-spec values for the clutch associated with 3rd gear can pinpoint the source of the slip.

Real Owner Repair Stories

• hdrams.com forum user 'JimKIII' (2022 Ram 2500 with 6.4L Hemi and 8HP75-LCV transmission, 26,000 miles) — P0733 'Gear 3 Incorrect Ratio' code with 'Service Transmission' message on the dash.
  ❌ Tried (didn't work) Initial dealer diagnosis pointed to a faulty valve body.
  ✅ What actually fixed it The manufacturer (RAM) required the dealer to drop the transmission pan before approving the valve body replacement. Upon inspection, metal shavings were found in the pan, which confirmed internal failure. The final fix was a complete transmission replacement, which was covered under warranty.
• 5thgenrams.com forum user (2019 Ram 1500 5.7L with 8-speed transmission) — After sitting for a few days, experienced a hard clunk on 1-2 and 2-3 shifts, followed by the check engine light and getting stuck in 3rd gear (limp mode). Code P0733 was stored. Restarting the truck made the symptoms disappear temporarily.
  ❌ Tried (didn't work) Clearing the code (it came back)., Initial dealer visit found no issues as the code was cleared and symptoms were not present.
  ✅ What actually fixed it The user's story is unresolved in the thread, but the symptoms strongly align with other reports that eventually lead to valve body or transmission replacement, indicating a recurring mechanical or hydraulic issue rather than a one-time glitch.

When the Usual Fixes Don't Work

• In one detailed owner account on the hdrams.com forum, the dealer's initial diagnosis for P0733 was a faulty valve body. However, manufacturer warranty procedure required dropping the pan for inspection first. This step revealed metal shavings, changing the diagnosis from a valve body repair to a necessary full transmission replacement, demonstrating that the valve body is not always the final answer even when it's the first suspect after software is ruled out.

OEM Part Supersession History

• 68563806AA → 68563806AB — Part update or revision by the manufacturer.
  Heads up: Part 68563806AB is specified for use on or after 04/09/21.

Model Year Variations Within This Range

• 2019+: The 2019 model year marked the introduction of the ZF 8-speed (8HP75-LCV) transmission paired with the 6.4L Hemi in the Ram 2500, replacing the previous 6-speed automatic. This change is significant as TSBs like 21-016-20 are specific to this newer transmission.
• 2025+: Starting in model year 2025, Ram Heavy Duty trucks with the Cummins engine will also move to a ZF 8-speed automatic transmission, replacing the Aisin 6-speed. This will change the diagnostic landscape for P0733 on future diesel models.