P0733 on 2013-2018 Ram 1500 8-Speed: Gear 3 Incorrect Ratio Causes and Fixes

What's Unique About the 2013-2018 Ram 1500

The 2013-2018 Ram 1500 uses a ZF-designed 8-speed automatic transmission (often the 8HP70). While generally robust, this platform has a well-documented pattern failure that causes the P0733 code. Chrysler/Ram has acknowledged a specific internal 'D' clutch assembly failure and issued Technical Service Bulletins (TSBs) to address it. This is critical information, as many repair shops might default to quoting a full, expensive transmission replacement when a more targeted and less costly repair is the manufacturer-recommended procedure.

Symptoms You May Notice

• Check Engine Light is on
• "Service Transmission" message on the dash
• Harsh, jerky, or delayed shifting, especially the 2-3 or 3-4 shift
• 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 🎬 Watch: Understanding common causes and fixes for the P0733 code.)
• A 'thump' or 'clunk' during the 2-3 shift, often described as a 'REV and CLUNK'
• Symptoms are often worse on a cold start and may temporarily disappear after restarting the truck
• Vehicle may not move in reverse

Most Likely Causes

1. Internal 'D' Clutch Assembly Failure 🔴 High Probability This is a widely acknowledged root cause for P0733 on this platform, with multiple Technical Service Bulletins (TSBs) issued by Ram. The failure is often due to a weak stamped backing plate in the clutch assembly that allows the clutch pack to flex, overheat, and burn out.
   How to confirm: A technician can confirm by verifying the presence of P0733 and related codes (like P1DA8, P1D92) as listed in TSB 21-009-25. The TSB applies to vehicles with over 7,000 miles. Finding metal debris in the transmission pan is a strong indicator. A definitive diagnostic step is to perform an air pressure test on the D-clutch circuit with the valve body removed, which will confirm an internal seal leak.
   Typical fix: Follow the repair procedure in TSB 21-009-25, which involves removing and disassembling the transmission to replace the faulty clutch assembly with an updated part kit. 🎬 Watch: A detailed look at overhauling the ZF 8HP D-clutch. This avoids a full transmission replacement.
   Est. part cost: $400-$800
2. Low or Dirty Transmission Fluid ⚪ Low Probability While a universal cause for transmission issues, it's less likely to be the root cause of P0733 on this specific truck given the prevalence of the 'D' clutch issue. However, it's the first and easiest thing to check.
   How to confirm: The fluid level must be checked by a technician following a specific procedure, as this is a sealed transmission without a dipstick. The process involves the vehicle being level and the transmission fluid at a specific temperature (86°F-122°F).
   Typical fix: If low, top off with the correct fluid (Mopar ZF 8&9 Speed ATF) and check for leaks. If dirty, a fluid and filter change may be attempted, but it is unlikely to fix the code if the D-clutch has already failed mechanically.
   Est. part cost: $150-$300

Rare But Worth Checking

• Faulty Valve Body or Shift Solenoid: While possible, this is a much less common cause for P0733 on this platform compared to the D-clutch failure. A bad solenoid or valve body can cause shifting issues, but the pattern failure points strongly to the clutch pack. Diagnosis often requires an advanced scan tool to monitor solenoid performance and check Clutch Volume Index (CVI) values.
• Faulty Transmission Speed Sensor: An input or output speed sensor providing incorrect readings can trick the TCM into thinking there's a ratio error. This would often be accompanied by other sensor-specific codes and is considered a less likely cause.
• Damaged Wiring or Connectors: Corrosion or damage to the main transmission harness or connector can interrupt signals. It's always worth inspecting the large connector on the transmission for pushed-out pins or corrosion, especially if other electrical issues are present. The TCM power and ground circuits are critical.

Diagnosis Steps

1. Verify code P0733 with an OBD-II scanner and check for other related codes, such as P1DA8 or P1D92.
2. Check for applicable Technical Service Bulletins (TSBs). TSB 21-009-25 (and its revisions) is highly relevant for this specific issue.
3. Perform a transmission fluid level and condition check. This must be done by a qualified technician following the correct temperature-specific procedure for this sealed transmission.
4. Inspect the transmission wiring harness and main connector for any visible damage, corrosion, or loose connections.
5. Using a capable scan tool (like wiTECH), check the Clutch Volume Index (CVI) values. A high CVI number for a specific clutch pack can indicate it is worn out.
6. If fluid is correct and TSBs apply (vehicle over 7,000 miles), a technician may perform an air pressure test on the D-clutch circuit to definitively confirm an internal leak before disassembly.
7. If the TSB conditions are met, proceed with the internal clutch repair outlined in TSB 21-009-25.
8. If the TSB does not seem to apply, further diagnosis of the valve body, solenoids, and speed sensors is required using an advanced scan tool.

Parts You'll Likely Need

• 'D' Clutch Assembly Repair Kit (OEM #68676891AB) — This is the specific fix outlined in manufacturer TSBs for the most common cause of P0733 on this vehicle.
  Trusted brands: Mopar
  OEM price range: $400-$800
• Transmission Pan/Filter Assembly (OEM #68225344AA or 52854834AB (Verify by VIN)) — The filter is integrated into the pan and is replaced as a unit during a fluid service or internal repair.
  Trusted brands: Mopar, ZF
  OEM price range: $150-$250
  Aftermarket price range: $100-$200
• Mopar ZF 8&9 Speed ATF (OEM #68218925AB) — This is the required fluid for any service on the 8-speed transmission. Approximately 8-10 quarts are needed for this repair.
  Trusted brands: Mopar
  OEM price range: $25-$40 per quart

Related Codes That Often Appear With This One

• P1DA8 — This code, for 'Incorrect Gear Ratio Clutch A, B, or D Defective', is specifically mentioned in TSB 21-009-25 as being related to the same internal clutch failure.
• P1D92 — Also related to 'Incorrect Gear Ratio - Clutch 4 Defective', this code is another indicator cited in the TSB for the same internal failure.

Technical Service Bulletins (TSBs) & Recalls

• 21-009-25 REV. C: Outlines the conditions (P0733, P1DA8, P1D92) and repair procedure for the faulty 'D' clutch assembly in various Stellantis vehicles with the 8-speed transmission.
• 9100534: A related bulletin that explicitly states that for DTC P0733, a repair is available and transmission replacement is NOT required, referencing TSB 21-009-25.
• Bulletin #S2621000003: Notes that vehicles may exhibit a transmission or check engine warning indicator for the 8HP70 and other 8-speed transmissions associated with fault code P0733.
• Bulletin #S2621000003 REV.A: A manufacturer service bulletin stating that 8HP70 and 8HP90 transmissions may exhibit diagnostic code P0733 among other gear ratio and performance faults.

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. C) 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 shift of the day, which then throws the code. Often, restarting the truck temporarily clears the symptom and limp mode, but the problem reoccurs.

Mechanic-Grade Diagnostic Values

• Clutch Pack Air Pressure Test — expected: A clear 'thump' as the clutch applies and holds pressure with no audible leaks. The piston should retract when air is removed.. Failure: A hissing sound indicates a leaking seal. No sound or movement indicates a blocked passage or seized piston.
• Clutch Volume Index (CVI) — expected: Varies by clutch pack and transmission model. For example, on a similar Chrysler 62TE, the Overdrive (OD) clutch CVI should be 48-150. The 8HP70 will have its own specific ranges programmed into the TCM.. Failure: A CVI number on the high side or out of the specified range indicates the clutch pack is worn. A number below the range can indicate a binding clutch.
• TCM Supply Voltage — expected: Between 10 and 16 volts with the ignition in the 'Run' position.. Failure: Voltage below 10V can cause erratic TCM behavior and false codes.

Scan Tool Commands That Help

• wiTECH, Autel, AlfaOBD: Quick Learn — This function resets and relearns the transmission's shift points. It is recommended after replacing major transmission components (like a valve body or the entire unit) or sometimes after disconnecting the battery to resolve harsh or delayed shifting.
• wiTECH: Adaptation Drive Learn Procedure — After a transmission repair/replacement or clearing adaptation memory cells, this guided driving procedure must be performed to relearn clutch fill times and pressures. It requires driving under specific conditions (e.g., specific torque loads and speeds) to properly adapt the shifts.
• wiTECH: Clutch Volume Index (CVI) Display — During diagnosis, viewing the CVI values for each clutch helps a technician identify which specific internal clutch pack is worn or failing without disassembly.
• wiTECH: 3rd Gear Clutch Test — This is a specific diagnostic test mentioned for older Chrysler transmissions that allows a technician to command the 3rd gear clutch and monitor sensor data to isolate a fault.

Wiring & Ground Locations

• TCM Fuses — In the under-hood fuse box (TIPM) located on the driver's side of the engine bay.. A blown fuse can cut power to the TCM, causing shifting problems and various transmission codes. Key fuses to check include F21, F22, F33, F57, and F72, though the exact ones may vary by specific model and year.
• Transmission Range Sensor Connector — On the left side of the transmission housing.. This connector houses wiring for the range sensor, which tells the TCM the driver's selected gear. Damage or corrosion here can lead to incorrect gear readings and shifting faults.
• Main Transmission Harness Connector — Large, round connector on the transmission case, typically on the passenger side.. This is the primary interface between the vehicle's wiring and all transmission solenoids and sensors. Pushed-out pins, corrosion, or harness chafing can cause intermittent signal loss for speed sensors or solenoids, potentially triggering a P0733 code.

Real Owner Repair Stories

• Reddit user on r/ram_trucks (2017 Ram 1500 with Hemi and 8-Speed) — Rough shift on the first shift of the day when cold, which got progressively worse over months. Eventually, a rough shift into 3rd gear triggered the check engine light with code P0733.
  ❌ Tried (didn't work) Letting the truck warm up for 5-20 minutes before driving, which initially helped but eventually became ineffective.
  ✅ What actually fixed it The user was advised by a professional in the thread that the symptoms point directly to an internal failure. The recommendation was to expect a valve body replacement at a minimum, but more likely a full transmission replacement or rebuild if significant metal debris was found in the pan.

"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 an electrical issue like 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

• 68676891AA → 68676891AB — This part number, described as an 'Output Shaft Kit', is the repair kit specified in TSBs for the D-clutch failure. The change from 'AA' to 'AB' indicates a revision to the part, likely to improve durability and prevent the original failure mode.

Model Year Variations Within This Range

• 2013-2018: The 8-speed transmission used with the 3.6L Pentastar V6 is the 845RE, which is manufactured by Chrysler under license from ZF. The transmission used with the 5.7L Hemi V8 is the 8HP70, which was sourced directly from ZF in Germany. While internally very similar and sharing the same design flaw, there can be minor differences in parts and software.

Diagnostic Flowchart

Other Known Issues on This Vehicle

Issues unrelated to this code that are worth knowing about as an owner of this generation:

• Exhaust Manifold Bolt Failure ('Hemi Tick') 🟠 Medium — Very common, especially on 5.7L HEMI engines. The ticking noise is most noticeable on cold starts and may disappear as the engine warms up. Can occur at various mileages, often after 60,000 miles.
• Camshaft/Lifter Failure ('Hemi Tick') 🔴 High — Less common than manifold bolt failure but much more serious. Often presents as a persistent ticking or tapping noise from the engine's top end. If not addressed, it can lead to catastrophic engine failure.
• Air Suspension Leaks 🟠 Medium — Common on trucks equipped with the optional four-corner air suspension. Failures often occur in the rubber air springs, causing the truck to sag at one or more corners, especially after being parked overnight.
• Infotainment System Glitches (Uconnect) 🟡 Low — Owners report occasional issues like the screen freezing, radio cutting out, or phantom touches. These are often resolved with a software update rather than hardware replacement.
• Fuel Level Sensor Failure 🟡 Low — A known issue where the fuel gauge suddenly drops to empty, triggering a low fuel light and chime, often accompanied by code P0463. The remote start may also be disabled. The fix requires dropping the fuel tank to replace the sensor.

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For a P0733 code on this platform, buying a complete used transmission assembly from a reputable salvage yard can be a viable, though risky, alternative to the TSB repair, especially if your transmission has extensive damage beyond just the D-clutch. It is generally not recommended to buy individual used internal components like clutch packs or valve bodies.

Donor-vehicle mileage cap: roughly under 60000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• Verify the donor vehicle's VIN to ensure it's the correct transmission model (8HP70 for Hemi, 845RE for V6).
• Obtain a vehicle history report for the donor to check for reported accidents or maintenance issues.
• Ask for a warranty from the salvage yard, typically 30-90 days.
• Inspect the fluid by draining a small amount from the pan if possible. Look for a bright red color and avoid any fluid that is dark, burnt-smelling, or contains visible metal particles.
• Check the main electrical connector for bent pins, corrosion, or damage.

OEM-only on this vehicle (don't cheap out):

• 'D' Clutch Assembly Repair Kit (Part No. 68676891AB). Using the official Mopar kit is essential to ensure you have the updated, corrected parts specified by the TSB.
• Transmission Fluid (Mopar ZF 8&9 Speed ATF). Using the correct OEM fluid is critical for shift quality and longevity; using non-specified fluid can cause issues.

Aftermarket brands forum-validated for this vehicle:

• Sonnax: Known for producing heavy-duty and problem-solving aftermarket transmission parts, including upgraded pressure plates and valve body components for the 8HP series.
• Southern Hotrod (SHR): Offers remanufactured and performance-upgraded valve bodies for the 8HP70/8HP90.
• Pure Drivetrain Solutions: Provides performance-oriented valve body upgrades and full transmission rebuilds.

Brands owners have reported issues with on this vehicle:

• No-name or unverified online sellers of 'remanufactured' valve bodies or transmissions. A proper remanufacturing process with testing on a dyno or valve body tester is critical.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P1DA8 — Companion code listed in TSB 21-009-25. It often appears with P0733 when the internal 'D' clutch assembly fails.
• P1D92 — Companion code listed in TSB 21-009-25. It is frequently set alongside P0733, indicating the known 'D' clutch assembly failure.

Frequently Asked Questions