P0733 on 2014-2021 Ram 1500: Gear 3 Incorrect Ratio Causes and Fixes

What's Unique About the 2014-2021 Ram 1500

The 2014-2021 Ram 1500 uses a ZF-designed 8-speed automatic transmission (like the 8HP70, 8HP75, or 850RE). While generally reliable, this platform has a documented history of a specific internal clutch failure that triggers P0733. Manufacturer TSBs specifically address this, outlining a repair procedure that involves replacing a clutch assembly rather than the entire transmission. This is critical information, as some shops may incorrectly quote a full transmission replacement costing thousands, when the manufacturer has explicitly stated a targeted repair is available.

Diagnostic Flowchart

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

Generation note: This range covers the end of the 4th generation Ram 1500 (2014-2018, 'DS' platform) and the start of the 5th generation (2019-2021, 'DT' platform). Both generations use the 8-speed automatic transmission (8HP70/8HP75/850RE) and are susceptible to the internal issues that cause code P0733, as confirmed by TSBs covering vehicles in both generations.

Symptoms You May Notice

• Check Engine Light is on
• Harsh or jerky shifting, especially into 3rd gear
• Engine RPMs flare up without an increase in vehicle speed (slipping)
• Vehicle enters "limp mode" (gets stuck in a single gear, often 3rd or 4th)
• Delayed or failed engagement into gear
• Transmission may refuse to shift past a certain gear
• Vehicle will not move in reverse (also noted in TSB 21-009-25)
• A 'thump' or 'clunk' during the 2-3 shift

Most Likely Causes

1. Internal 'D' Clutch Assembly Failure 🔴 High Probability Multiple Technical Service Bulletins (TSBs), including #21-009-25, have been issued by the manufacturer specifically for this failure on Ram 1500s with 8-speed transmissions. The TSBs point to a defect in the 'D' clutch assembly, which is used in gears 4 through 8 and reverse. This is the most widely acknowledged root cause for this specific code on this platform.
   How to confirm: A technician would confirm this by verifying the presence of P0733 and/or related codes P1DA8 and P1D92, as listed in the TSB. The TSB applies to vehicles with at least 7,000 miles. In some cases, dealers are required by the manufacturer to drop the transmission pan and take pictures of any metal debris found before approving the warranty repair.
   Typical fix: Follow the repair procedure in TSB 21-009-25, which involves removing and disassembling the transmission to replace the faulty clutch pack with a specific repair kit. TSB #9100534 explicitly states that transmission replacement is NOT required for this issue. The repair is labor-intensive, with a book time of around 9.7 hours.
   Est. part cost: $200-$400 for the OEM clutch repair kit.
2. Low or Degraded Transmission Fluid 🟡 Medium Probability These transmissions are 'sealed' and do not have a dipstick, making fluid level checks difficult for the average owner. A low fluid level can cause a loss of hydraulic pressure, leading to slipping. The fluid check procedure is specific, requiring the vehicle to be level and the fluid to be at a certain temperature (between 30°C/86°F and 50°C/122°F).
   How to confirm: The fluid level must be checked via a specific procedure that involves bringing the transmission to the correct temperature range and opening a check plug while the vehicle is level and running. The fluid condition (dark, burnt smell) should also be assessed. ZF fluid has a natural illuminance under a black light, and adding dye is not recommended as it can cause shift quality issues.
   Typical fix: Perform a transmission fluid and filter service. The pan contains an integrated filter and is typically replaced as a unit. Use only the specified Mopar ZF 8&9 Speed ATF or a compatible high-quality equivalent. A fluid change alone is unlikely to fix a recurring P0733 if it's caused by the mechanical D-clutch failure.
   Est. part cost: $150-$300 for a new pan/filter and fluid.
3. Faulty Valve Body or Shift Solenoid ⚪ Low Probability The valve body directs hydraulic fluid to engage the clutches. A sticking solenoid or blocked passage can prevent proper gear engagement. Some owners on forums have discussed attempting to fix sticking solenoids with a transmission fluid additive as a last-ditch effort before a major repair, with mixed results.
   How to confirm: A professional scan tool can command individual solenoids to test their function. The valve body can be inspected for debris or damage once the transmission pan is removed. In one documented case, a dealer initially diagnosed a bad valve body, but further inspection revealed metal in the pan, leading to a full transmission replacement approval.
   Typical fix: Replacement of the faulty solenoid or the entire valve body assembly. This is less common than the D-clutch failure for this specific code.
   Est. part cost: $400-$1200 for a valve body assembly.

Rare But Worth Checking

• Faulty Transmission Speed Sensor: An input or output speed sensor providing incorrect readings can make the TCM believe there is a ratio error when there isn't. This is less common and would often be accompanied by other specific sensor-related codes (like P0716 or P0721).
• Damaged Wiring or Connectors: Corrosion or damage to the main transmission harness can interrupt signals between the sensors, solenoids, and the TCM, leading to various shifting faults. It's recommended to check the large connector on the transmission for corrosion or pushed-out pins.
• TCM Software Glitch: In some cases, particularly on newer models, a TCM software glitch can incorrectly flag a ratio error. TSB #21-007-20 was issued for 2020 Ram 1500s where P0733 would set prematurely while in 4-Lo, with the fix being a TCM reflash, not a mechanical repair.

Diagnosis Steps

1. Verify the code P0733 and check for other related codes (like P1DA8, P1D92) using an OBD-II scanner.
2. Check for applicable Technical Service Bulletins (TSBs). TSBs 21-009-25 and 21-039-24 are highly relevant for the mechanical D-clutch failure. Check TSB 21-007-20 if the issue only occurs in 4-Lo on a 2020 model.
3. Perform a transmission fluid level and condition check. This must be done by a qualified technician following the correct procedure for this sealed transmission, which involves specific temperatures (30°C-50°C or 86°F-122°F) and ensuring the vehicle is level.
4. If fluid is low, top it off and check for leaks. If the fluid is very dirty or burnt, a fluid and filter change may be attempted, but it is unlikely to fix an internal mechanical issue like the D-clutch failure.
5. Inspect the transmission wiring harness and main connector for any visible damage, corrosion, or loose connections.
6. If the fluid level is correct, the vehicle has over 7,000 miles, and the D-clutch TSBs apply, the next step is to proceed with the internal clutch repair outlined in TSB 21-009-25.
7. If the TSB does not apply, further diagnosis of the valve body, solenoids, and speed sensors is required using an advanced scan tool. A technician may perform a 'Quick Learn' or 'Reset Adaptive Values' procedure using a tool like wiTECH.

Parts You'll Likely Need

• D Clutch Repair Kit (OEM #68676887AB) — This is the specific kit called for in TSB 21-009-25 to fix the most common cause of P0733 on these trucks (for 4x4 DS, DT models). Other part numbers exist for different drivetrain configurations (e.g., 68239499AD for AWD, 68676894AB for RWD). This part number supersedes 68676887AA.
  Trusted brands: Mopar
  OEM price range: $200-$400
  Aftermarket price range: N/A
• Transmission Oil Pan and Filter Assembly (OEM #68225344AA) — The filter is integrated into the plastic oil pan and must be replaced as a single unit during any service that involves dropping the pan. This part fits a wide range of Stellantis vehicles with the ZF 8-speed.
  Trusted brands: Mopar, Dorman, ZF
  OEM price range: $150-$250
  Aftermarket price range: $80-$150
• Mopar ZF 8 & 9 Speed ATF (OEM #68218925AB) — This is the required fluid for the 8-speed transmission. Using the correct fluid is critical for transmission performance and longevity. A full service requires multiple quarts.

Related Codes That Often Appear With This One

• P1DA8-00 — This code for 'Incorrect Gear Ratio Clutch A, B or D Defective' is explicitly mentioned in the same TSBs as P0733 and points to the same internal clutch failure.
• P1D92-00 — This code for 'Incorrect Gear Ratio - Clutch 4 Defective' is also listed alongside P0733 in the manufacturer TSBs, indicating a related internal fault.

Technical Service Bulletins (TSBs) & Recalls

• 21-009-25 REV. B / REV. C: Outlines the conditions (P0733, P1DA8, P1D92) and repair procedure for the faulty 'D' clutch assembly.
• 9100534: Explicitly states that for DTC P0733, a repair is available and transmission replacement is NOT required, referencing TSB 21-009-25.
• S2621000003 / REV.A: Lists P0733 as a potential fault code for the 8HP series transmissions.

Platform-Specific Known Issues

• A known defect with the 'D' clutch assembly is the most frequent cause of P0733. Ram has issued multiple TSBs (e.g., 21-009-25 Rev. B, 9100534) acknowledging the problem and providing a specific repair procedure that avoids full transmission replacement.
• Owner experiences on forums frequently describe the symptoms starting on a cold start, with a hard shift or slip on the first 2-3 or 3-4 shift of the day, which then throws the code. Often, restarting the truck temporarily clears the symptom, but the problem reoccurs.

Mechanic-Grade Diagnostic Values

• Shift Solenoid Resistance — expected: 5.0 Ohms at 20°C (68°F). Failure: A reading significantly higher or lower than 5.0 Ohms indicates a faulty solenoid coil.
• Transmission Fluid Temperature for Level Check — expected: Between 30°C (86°F) and 50°C (122°F). Failure: Checking the fluid when it is too cold or too hot will result in an inaccurate level reading, which can lead to misdiagnosis.
• Solenoid Vacuum Test — expected: Holds over 20 in-Hg. Failure: Any reading below 20 in-Hg indicates a compromised solenoid with an internal leak that should be replaced.

Hidden / Shadow Codes Worth Checking

• P1DA8-00: Incorrect Gear Ratio Clutch A, B or D Defective. This is a manufacturer-specific code that often appears with P0733 and points directly to the same internal D-clutch failure. (see via Dealer-level scan tools like wiTECH or advanced aftermarket scanners.)
• P1D92-00: Incorrect Gear Ratio - Clutch 4 Defective. Also listed in the same TSBs as P0733, this code further confirms the fault lies within the transmission's internal clutch assemblies. (see via Dealer-level scan tools like wiTECH or advanced aftermarket scanners.)

Scan Tool Commands That Help

• wiTECH (or AlfaOBD for 2018+ with bypass): Reset Adaptive Values — This function clears the TCM's learned clutch fill times and pressures. It should be performed after any major transmission repair, such as an overhaul or valve body replacement, to force the system to relearn. Note that simply clearing this may cause poor shifting until the transmission relearns.
• wiTECH (or AlfaOBD for 2018+ with bypass): Quick Learn — This is a guided procedure that allows the TCM to quickly relearn clutch adaptive values after they have been reset or after a repair. It is a critical step to ensure proper shift quality after service.
• wiTECH: Adaptation Drive Learn Procedure — Used to resolve customer complaints of poor shift quality that persist after a Quick Learn. It involves a specific, lengthy road test procedure while monitoring the scan tool to fine-tune the clutch adaptations.

Wiring & Ground Locations

• Transmission Range Sensor Connector — On the left side of the transmission case.. Damage or corrosion to this connector could send incorrect gear position data to the TCM, potentially contributing to ratio faults, although it's a less common cause for P0733.
• Transmission Main Connector — The main electrical harness connector on the transmission case.. This is the single point of connection for all electronic signals to and from the transmission (solenoids, speed sensors, temp sensor). Corrosion or pushed-out pins here can cause a wide range of faults, including P0733.

Real Owner Repair Stories

• AR15.com forum user (2015 Ram 1500 5.7L, 77,000 miles) — Banged into reverse on a cold start, then lurched when shifting into 3rd or 4th, triggering code P0733.
  ❌ Tried (didn't work) Restarting the truck (issue was intermittent).
  ✅ What actually fixed it A complete Dodge remanufactured transmission was installed. The technician noted an excessive amount of metal in the old transmission fluid and cooler, indicating severe internal failure.
• 5thGenRams forum user 'XDBrad' (2019 Ram 1500) — Harsh 2-3 shift described as 'REV and CLUNK', followed by check engine light and limp mode (stuck in 3rd gear). Code P0733 was stored.
  ❌ Tried (didn't work) Clearing the code (it returned)., Restarting the truck (provided a temporary fix).
  ✅ What actually fixed it The dealer confirmed the internal failure. The final resolution involved a lengthy back-and-forth with RAM corporate, highlighting the conflict between the dealer wanting to replace the entire transmission and RAM wanting to perform the TSB-specified internal rebuild.

"I Checked Everything" — The Actual Cause

• For code P0733, the equivalent of a 'smoke test clean' scenario is when the transmission fluid level and condition are found to be perfect. A technician might check the fluid, find it full and clean, and suspect a sensor or solenoid. However, the most common underlying cause on this platform, the internal 'D' clutch failure documented in TSB 21-009-25, cannot be seen by checking the fluid. The true failure is mechanical and hidden inside the transmission case, making it a classic example of where initial, non-invasive checks appear normal despite a serious internal fault.

OEM Part Supersession History

• 68676887AA → 68676887AB — Revision or update to the D-Clutch repair kit components.

Model Year Variations Within This Range

• 2014-2018 ('Classic' V8): These models typically use the ZF-made 8HP70 transmission when paired with the 5.7L HEMI V8.
• 2019-2021 ('DT' V8): The 5th generation Ram 1500 with the 5.7L HEMI V8 was upgraded to the ZF 8HP75 transmission, which has a higher torque capacity.
• 2014-2021 (V6): Models with the 3.6L Pentastar V6 generally use the Chrysler-built 845RE or 850RE transmission, which are licensed versions of the ZF 8HP45 and 8HP50, respectively. Despite the different model numbers, they share the same fundamental design and are also affected by the D-clutch failure TSBs.