P0735 on 2020-2024 Ram 2500: Gear 5 Incorrect Ratio Causes and Fixes

What's Unique About the 2020-2024 Ram 2500

On the 2020-2024 Ram 2500, particularly those with the 68RFE transmission, P0735 is often linked to hydraulic pressure issues. The 68RFE is known for specific vulnerabilities, including a higher rate of solenoid failure and issues with the Overdrive (OD) clutch pack, which is used for 5th and 6th gear. Manufacturer Technical Service Bulletins (TSBs) point towards problems with transmission fluid pressure and associated sensors. [Bulletin #18-069-25, Bulletin #21-012-25 REV. E] Additionally, a safety recall (ZA3 / NHTSA 22V-835) for some 6.7L models addresses a build-up of pressure and heat that can expel fluid, highlighting the importance of the transmission's hydraulic and thermal management systems. For 2019 and newer models, the 68RFE also features an auxiliary valve body with its own torque converter clutch solenoid, adding another layer to the diagnosis.

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 is on
• Transmission warning lamp illuminated
• Delayed or harsh shifting into 5th gear
• Transmission slipping (engine RPMs flare up without an increase in speed)
• Inability to shift into 5th gear
• Vehicle enters "limp mode," getting stuck in one gear
• Loss of power and poor acceleration
• Reduced fuel economy
• Jumping out of 5th or 6th gear with slight throttle application

Most Likely Causes

1. Low or Contaminated Transmission Fluid 🔴 High Probability → Shop Transmission Assembly A recall for some models (ZA3 / 22V-835) addresses potential fluid expulsion due to heat and pressure, which could lead to low fluid levels. Low fluid reduces hydraulic pressure, preventing proper gear engagement. The 68RFE is also sensitive to fluid condition, and contamination can clog filters and solenoid screens.
   How to confirm: Check the transmission fluid level and condition. The fluid should be at the correct level, red in color, and not smell burnt. Note: Many modern trucks lack a traditional dipstick, requiring a specific service procedure to check the level, often by removing a check plug on the transmission pan when the fluid is at a specific temperature.
   Typical fix: Top off or replace the transmission fluid and filter. Use only the manufacturer-specified fluid (e.g., Mopar ATF+4 or equivalent).
   Est. part cost: $100-$250
2. Faulty Transmission Fluid Pressure Sensor/Transducer 🟡 Medium Probability → Shop Transmission Assembly TSB #18-069-25 directly links P0735 with hydraulic pressure sensor codes (P0868, P0933), indicating this is a known issue for Ram. These sensors are critical for the TCM to manage shift pressures, and failure can lead to erratic shifting or slipping.
   How to confirm: Scan for other codes, specifically P0868 or P0933. A technician can perform a line pressure test to compare actual pressure to the sensor's readings. The sensor is located inside the transmission on the valve body.
   Typical fix: Replace the transmission fluid pressure sensor/transducer. This requires dropping the transmission pan and removing the valve body to access the sensor. 🎬 See this walkthrough on swapping the transmission pressure sensor.
   Est. part cost: $150-$300
3. Failing Shift Solenoid Pack 🟡 Medium Probability → Shop Transmission Valve Body Solenoids are wear items that control the flow of hydraulic fluid to engage clutches. A solenoid that is stuck or failing electrically won't direct pressure correctly to engage 5th gear. The 68RFE solenoid pack is a known failure point. For 2019+ models, there are two different solenoid packs identified by connector color (white or blue), so verifying the correct one is crucial. 🎬 Watch: How to replace the 68RFE solenoid pack the right way.
   How to confirm: A diagnostic scan tool can be used to command the solenoid on and off to test its function. Resistance can also be checked with a multimeter. The solenoid pack is located on the valve body.
   Typical fix: Replace the entire solenoid pack assembly. This is typically done by dropping the transmission pan and accessing the valve body. Part numbers vary by year; for example, 2019+ models may use a blue connector pack (Suncoast SC-68RFE-BLUE). An older Mopar part number that has been superseded is 68353383AC.
   Est. part cost: $250-$500
4. Internal Transmission Failure ⚪ Low Probability → Shop Transmission Assembly Slipping that goes unaddressed generates heat that wears out internal components like clutch packs and seals. The 68RFE transmission in these trucks can be susceptible to wear in the OD (Overdrive) clutch circuit, which is used for 5th gear. Forum discussions frequently point to a burned OD clutch as the ultimate cause 🎬 Watch: A teardown showing common overdrive clutch failure points. if fluid and electronics are okay.
   How to confirm: If fluid and electronics checks pass, the next step is to drop the transmission pan and inspect for excessive metal debris or clutch material. This indicates internal mechanical damage.
   Typical fix: Requires a partial or complete transmission rebuild or replacement. Aftermarket solutions from companies like Jasper and Suncoast often include upgraded components to address known 68RFE weaknesses, such as improved snap rings and billet converter covers.
   Est. part cost: $2000-$6000+

Rare But Worth Checking

• TCM Software Issue: TSB #21-012-25 REV. E suggests that a software update can resolve a range of incorrect gear ratio codes, including P0735. Always check if your vehicle's software is up to date before performing expensive mechanical repairs.
• Faulty Valve Body: → Shop Transmission Valve Body The valve body is the hydraulic brain of the transmission. Internal blockages, cracks, or stuck valves can prevent proper pressure regulation for the 5th gear clutch circuit. This is often diagnosed after solenoids and fluid have been ruled out. Some owners opt for upgraded aftermarket valve bodies from brands like Revmax to improve shifting and durability.
• Faulty Powertrain Control Module (PCM): In rare cases, the PCM itself can be the source of the problem, incorrectly interpreting sensor data. One owner of a 2010 Ram 1500 with P0734 and P0735 replaced the PCM after changing speed sensors and the solenoid pack, which ultimately fixed the issue.

Diagnosis Steps

1. Check transmission fluid level and condition. Ensure it is full, clean, and does not smell burnt.
2. Use a professional scan tool to check for other transmission-related DTCs, especially pressure and sensor codes like P0868, P0933, and P0841.
3. Check for applicable TSBs (like 21-012-25 REV. E and 18-069-25) and recalls (like ZA3 / 22V-835) for your vehicle's VIN. A software update may be the required fix.
4. Inspect the transmission wiring harness and connectors for any damage, corrosion, or loose connections.
5. Perform a transmission line pressure test to verify the hydraulic pump is working correctly and compare readings to the pressure sensor data.
6. If pressure is low, drop the transmission pan. Inspect the fluid filter for clogs and the pan for excessive metal shavings or clutch material. Significant debris points to internal failure.
7. If the pan is relatively clean, test the shift solenoids for the 5th gear circuit. This can be done with a scan tool or by checking resistance.
8. If significant debris is found in the pan, internal mechanical failure (likely the OD clutch pack) is the cause, and the transmission will need to be removed for inspection and repair.

Parts You'll Likely Need

• Transmission Fluid and Filter — The first and most crucial step. Low or degraded fluid is a primary cause of low hydraulic pressure leading to this code.
  Trusted brands: Mopar
  OEM price range: $150-$250
  Aftermarket price range: $100-$180
• Transmission Fluid Pressure Sensor/Transducer (OEM #68377000AB (superseded part number)) — A common failure point identified in Ram TSBs. A faulty sensor provides incorrect pressure data to the TCM, causing shifting issues.

Related Codes That Often Appear With This One

• P0868 — Indicates low transmission fluid pressure, a primary cause for clutch slip and incorrect gear ratios. TSB #18-069-25 and #21-012-25 REV. E explicitly link this code with P0735.
• P0933 — Indicates a fault with the hydraulic pressure sensor's performance. TSB #18-069-25 links this directly to P0735, pointing to a sensor or hydraulic circuit problem.
• P0734 — Incorrect Gear Ratio in 4th gear. If you see multiple gear ratio codes, it points to a more systemic problem like low fluid pressure, a failing torque converter, or widespread clutch pack failure.
• P0841 — Indicates a performance issue with the transmission fluid pressure sensor. TSB #21-012-25 REV. E groups this with P0735, suggesting a software update or sensor replacement may be needed.

Technical Service Bulletins (TSBs) & Recalls

• 21-012-25 REV. E: Addresses multiple incorrect gear ratio DTCs, including P0735, potentially fixed by a PCM software update.
• 18-069-25: Links P0735 with transmission fluid pressure codes, suggesting a hydraulic sensor or circuit issue.

Platform-Specific Known Issues

• Owner Experience: Burned Overdrive Clutch: Multiple owners on forums for both diesel (68RFE) and gas (66RFE) Ram HD trucks report that after ruling out fluid and electronics, the root cause of P0735 was a burned Overdrive (OD) clutch pack. This requires transmission removal and at least a partial rebuild to replace the clutch plates.
• Repair Story: Upgraded Valve Body: → Shop Transmission Valve Body To combat the mushy shifts and potential for pressure loss in the 68RFE, some owners proactively replace the stock valve body with a high-performance unit from a company like Revmax. One owner noted significantly crisper shifts and resolved pressure-related codes after installing an upgraded valve body and a transmission tune.

Mechanic-Grade Diagnostic Values

• Shift Solenoid Resistance (UD, OD, 2C, 4C, LR/TCC) — expected: 1.3 Ohms (at room temperature). Failure: An open circuit or resistance significantly different from 1.3 Ohms indicates a faulty solenoid coil.
• Pressure Control Solenoid Resistance — expected: 4.9 Ohms. Failure: An open circuit or resistance significantly different from 4.9 Ohms indicates a faulty solenoid.
• Line Pressure vs. Desired Line Pressure (Scan Tool) — expected: Actual line pressure reading should be within 10 psi of the desired line pressure reading.. Failure: If the actual pressure is more than 10 psi below the desired pressure, it indicates a problem with the oil filter, pump, main regulator valve, or a hydraulic leak.
• Overdrive (OD) Clutch Pack Clearance — expected: .030 - .063 inches. Failure: Clearance outside this range indicates improper assembly or worn components.

Hidden / Shadow Codes Worth Checking

• P1790: Fault, Last Shift. This is not a primary code but can be found in the 'Event Data' on a scan tool. If P1790 is present with a 'Target Gear' of 5th, it helps confirm the fault occurred during a 5th gear shift attempt. (see via Professional scan tool capable of reading detailed Event Data from the TCM.)

Scan Tool Commands That Help

• wiTECH, Autel, AlfaOBD, or other professional scanner: Quick Learn — This procedure is mandatory after replacing the transmission, valve body, or solenoid pack. It allows the TCM to learn the hydraulic and mechanical characteristics of the new components to ensure proper shift timing and feel.
• wiTECH or equivalent dealer-level tool: Update TCC Solenoid P/I Data — On 2019 and newer models, if the valve body or the standalone Torque Converter Clutch (TCC) solenoid is replaced, the unique Pressure/Inductance (PI) curve data from the new part must be programmed into the PCM. The data is typically provided as a QR code with the replacement part.

Wiring & Ground Locations

• Solenoid Connector Pin 7 — On the main 23-pin round connector at the transmission case.. This is the control circuit for the Overdrive (OD) solenoid, which is directly involved in the 4-5 shift. A wiring issue at this pin can prevent the solenoid from activating.
• Solenoid Connector Pin 10 — On the main 23-pin round connector at the transmission case.. This is a primary power feed from the transmission control relay. Loss of power on this pin will disable multiple solenoids.
• PCM/Body Grounds — Various points on the engine block and chassis, particularly the main ground straps from the battery.. Poor grounds can allow radio frequency (RF) noise from the alternator to interfere with sensor signals and TCM operation, causing erratic torque converter lockup and shifting behavior that can be misdiagnosed as an internal transmission failure.

Real Owner Repair Stories

• YouTube user 'DIYTechnician' (2010 Ram 1500) — Persistent P0734 (Gear 4 Incorrect Ratio) and P0735 codes.
  ❌ Tried (didn't work) Replacing the input speed sensor, Replacing the output speed sensor, Replacing the transmission solenoid pack
  ✅ What actually fixed it Replacing the Powertrain Control Module (PCM). The owner purchased a refurbished unit, which resolved the codes after multiple other parts failed to do so.
• RamForum.com user 'trannyman' (2014 Ram 2500 w/ 6.4L HEMI) — P0735 code at 35,755 miles.
  ❌ Tried (didn't work) Initial diagnosis
  ✅ What actually fixed it The expert diagnosis was a burned Overdrive (OD) clutch pack, requiring transmission removal and teardown for replacement. This highlights the common mechanical failure path when fluid and electronics are ruled out.

"I Checked Everything" — The Actual Cause

• In the context of P0735, the equivalent of a 'clean smoke test' is when the fluid is clean, the pressure sensor tests okay, and the solenoids have correct resistance, yet the code persists. In these cases, the root cause is often a hidden mechanical or hydraulic issue. One common culprit is a cross-leak in the valve body, where the separator plate or warped casting allows high-pressure fluid to leak into the low-pressure overdrive circuit, causing clutch slip. Another possibility is a failing Powertrain Control Module (PCM) that is incorrectly processing sensor data, as seen in a real-world repair where replacing the PCM was the final solution after all common transmission parts were replaced.

When the Usual Fixes Don't Work

• While P0735 is most commonly caused by low fluid or a bad solenoid pack, there are documented cases where the actual fix was much less direct. In one instance involving a 2010 Ram, after replacing both speed sensors and the solenoid pack to no avail, the problem was ultimately solved by replacing the entire Powertrain Control Module (PCM). This suggests that in rare, hard-to-diagnose cases where all transmission-side components check out, the fault may lie within the control module itself. Another non-obvious cause can be electrical interference; some owners have traced erratic shifting and torque converter behavior, which can mimic a slip, to poor grounds or RF noise from the alternator, which was fixed by installing a noise filter rather than performing transmission repairs.

OEM Part Supersession History

• White Connector Solenoid Pack (e.g., Mopar 5170877AF) → Gray Connector Solenoid Pack (2011-2018), Blue Connector Solenoid Pack (2019+) — Design changes to improve performance and accommodate electronic strategy updates.
  Heads up: The Gray connector pack (2011-2018) eliminated the OD solenoid and CANNOT be used in earlier models. The Blue connector pack (2019+) re-added a sixth solenoid and works with a new standalone TCC solenoid, making it incompatible with any pre-2019 vehicle.

Model Year Variations Within This Range

• 2020-2024: These models use the 'Blue Connector' solenoid pack introduced in 2019. This pack has six solenoids and works in conjunction with a separate, standalone Torque Converter Clutch (TCC) solenoid mounted on the valve body. This is a major parts difference from 2011-2018 models.
• 2020-2024: Replacing the TCC solenoid or valve body requires programming the new component's Pressure/Inductance (PI) data into the PCM using a dealer-level scan tool. This data is unique to each part and is usually supplied via a QR code.
• 2020-2024: These vehicles are equipped with a Secure Gateway Module (SGM) which restricts access for aftermarket scan tools. Performing a 'Quick Learn' or other service functions requires either a bypass cable for tools like AlfaOBD or an authorized scan tool with an active FCA AutoAuth subscription.