transmission problem

Troubleshooting Jeep Transmission Problems

Transmission problems on Jeep vehicles, such as erratic shifting, slipping, delayed shifting, and no shifting, are often caused by low transmission fluid levels. The same symptoms can also indicate a  serious transmission problem, such as a faulty valve body, work, clutches, and a faulty torque converter.

This guide goes over common problems and step-by-step instructions to help you troubleshoot Jeep transmission problems such as limp mode, no shifting, delayed shifting, and slipping on Jeep Wrangler, Grand Renegade, Compass, Gladiator, and Cherokee.

Possible Causes

Jeep Valve Body

Common problems that often cause Jeep transmission problems:

  • Low transmission fluid level – Low transmission fluid level can cause several issues, including erratic shifting, no shifting at all, delayed shiting, strange grinding noises, limp mode, and even checking the engine light to come on.
  • Faulty Torque Converter – This can cause Jeep transmission to slip in all gears, shudder, and even overheat.
  • Worn Bands –  Can cause delayed shifting, shifting at high RPM, harsh shifting, no gear at all, no reverse.
  • Shifter Module – A faulty shifter module or shifter cable can cause the transmission to get stuck or not go in the selected gear.
  • Defective Valve Body – The valve body is very complex and can fail in several ways. Depending on the competent that fails, it can cause limp mode. The transmission may not shift at all or harsh shifts between gear or specific gear.
  • Faulty Vehicle Speed Sensor  – If your Jeep has developed a harsh shift or is stuck in emergency mode (limp mode), the vehicle speed sensor (VSS) may be the problem. Sigan from the VSS is sent to the Powertrain Control Module (PCM), and the last signal can cause one or more of the previous systems.
  • Brake Light Switch – A faulty brake light switch can prevent the shifter from moving out or back in Park.
  • Low Battery Voltage – In rare cases, the low battery voltage can trigger the automatic transmission to get stuck in limp mode.
  • PCM / TCU / ECU Software Issue – Software issues can cause erratic shifting or downshifting issues. Transmission may shift too late or gears to drop unexpectedly. This is a common problem for your particular transmission; a Jeep dealer may have a software update to fix such shifting problems.
  • Wire harness – Damages of wire harnesses from ECU / PCM to the transmission housing can cause shifting problems. For example, you may not shift at all or go in gear.

Most Common Jeep Transmission Problems

Jeep Transmsision Problems Wrangler Grand Cherokee Renegade Compass Gladiator

Based on our research and experience with Jeep vehicles, here is a list of the most common problems with Jeep transmission and possible causes.

Delayed or failed gear shifts

Older Jeep vehicles that use a 42RE or 42RLE 4-speed automatic transmission have a widespread issue with delayed or failed gear shifts. There are two different scenarios when this happens. One is when shifting through 1st to 3rd gear, and the other is shifting from 3th to 4th gear. In most cases, there will be no check engine light or other symptoms.

Possible causes

  • Worn or stuck governor pressure solenoid, preventing it from maintaining proper fluid pressure. This will affect 1st-3rd gear shifts. A faulty sensor or wiring issue will cause incorrect readings on the solenoid position.
  • Worn overdrive solenoid serves as a pressure accumulator that engages the overdrive gear. This will affect the 4th (overdrive) gear only. When this solenoid wears out, it cannot hold the transmission fluid pressure needed for proper operation.
  • Other possible causes include low transmission fluid levels or dirty transmission filters.

Torque converter or overdrive issues

Jeep, with a 42RE or 42RLE 4-speed automatic transmission made after 2000, can have sporadic torque converter clutch or overdrive engagement problems. Usually, this issue will trigger a ‘check engine’ warning light so that a corresponding code will be stored in ECU memory.

Possible causes

  • A broken cover plate holds the pressure boost valve on the bottom side of the valve body. This is a well-known problem, which is a result of poor design from the factory. As a result, the retaining bracket that holds the lockup pump breaks off. This triggers a P1740 code. Installing a special upgrade kit from Superior Solution is the best solution.
  • Faulty input/output speed sensors on the gearbox or faulty throttle position sensor. If any of them are giving the incorrect reading, it can affect the torque converter clutch performance. These issues will usually trigger various speed sensor-related codes.
  • Faulty governor pressure solenoid or the corresponding sensor, as already described.

Delayed or failed gear engagement

Jeeps that use a 545RFE 5-speed automatic transmission can develop a problem with gear engagement. This affects both drive and reverse gears and shows a noticeable delay with gear engagement when the vehicle is cold. The problem will be more apparent when outside temperatures are shallow. The check engine light may also come on.

Possible cause

  • Loose or disconnected transmission cooler filter. This allows the transmission fluid to drain from the torque converter when the vehicle is turned off for some time; it will delay gear engagement until the pressure builds up. Installing a modified filter solves the issue.
  • Dirty transmission fluid and filter, low fluid level, or improper transmission fluid

Delayed gear shifts or limp-home mode

Jeep vehicles with a Mercedes-sourced 722.6 5-speed automatic transmission can suffer from issues that range from harsh and delayed gear shifts to gear slippage or even going into limp-home mode. In most cases, these symptoms will be intermittent and trigger a check engine light to store a corresponding error code.

Possible causes

  • The faulty conductor plate holds the solenoids and connects them to the TCU. When the conductor plate is faulty, it causes communication problems, which results in improper solenoid operation. This is a well-known problem, and there are numerous aftermarket solutions.
  • Worn or faulty valve body solenoid. Sometimes, the problem can be due to damage to the internal wiring.

Erratic gear shifts or gear slipping.

Front-wheel drive Jeeps with an A6MF1 6-speed automatic transmission can develop issues with incorrect gear changes. Shifts can be erratic, or there can even be slippage during gear shifts. In most cases, the symptoms will be more noticeable when cold. There might be a check engine light and corresponding codes in DTC memory.

Possible causes

  • Leaking or sticking solenoids that engage each gear. This is a gradual process, which starts only when cold and gets worse with time. The only solution is replacing the whole solenoid set with new or upgraded ones.
  • Faulty or damaged solenoid wiring obstructs signals from the TCU. Checking and repairing or replacing the wiring will solve the issue.

Intermittent shifts to neutral

Front-wheel drive Jeeps with a ZF9HP48 9-speed automatic transmission can unexpectedly shift to neutral while driving. This issue is intermittent in most cases, and there will be no apparent correlation to driving conditions or overheating. This problem will trigger a check engine light, and a corresponding DTC code will be stored in the Engine Control Unit (ECU).

Possible cause

  • Faulty transaxle range sensor connector and wiring causes incorrect signals from the sensor. When the TCU detects an implausible signal, it shifts the transmission to neutral and sets the P0901 code. As this is a well-known and serious safety issue, a Service Bulletin covers it. Check if your vehicle is affected.

Troubleshooting Jeep Transmission Problems

Troubleshoot Jeep Transmission Problems

Follow the steps to troubleshoot and isolate Jeep transmission problems. It is critical to determine which transmission is installed on your Jeep to research the issues that affect that particular transmission. You can verify the transfer by Decoding your VIN or calling the dealer.

To help you get started, here is a list of Jeep transmissions:

  • 3-Spd Automatic A999: 1986-1991
  • 3-Spd Automatic 30RH (A904): 1994-1995
  • 3-Spd Automatic 30RH (A904): 1994-1995, 1997-2006
  • 4-Spd Automatic 42RLE: 2003-2006, 2007-2011
  • 5-Spd Automatic W5A580: 2012-2017
    • This is manufactured by Mercedes-Benz and is known as the 722.6 transmission. It is a reliable transmission but known to have a few minor issues. For more help, see our article on Mercedes-Benz 722.6 transmission problems.

The next step is to check the transmission fluid level. Low transmission fluid level is one of the most common issues that cause shifting issues on Jeep Wrangler, Gand Cherokee, Renegade, Compass, Gladiator, and Cherokee.

How to Check Jeep Transmission Fluid Level

Jeep Transmission Problems

This procedure should only be performed to check the transmission fluid that may be slightly low. If the transmission fluid is extremely low, you need to add fluid and then check the level. Checking the transmission fluid level on a transmission that has no fluid can damage the transmission.

  1. Park the vehicle on level ground when possible.
  2. Set the parking brakes and shifter in Park.
  3. Pull the hood release and open the hood.
  4. Locate the transmission dipstick.
  5. Remove the dipstick and clean it with a clean cloth.
  6. Reinsert the dipstick in the transmission. Ensure the transmission is fully inserted, then remove it.
  7. Look carefully at the dipstick to determine the current transmission fluid level. The level should be between MIN and MAX marks for the COLD (lower) markings.
  8. If the level is low, add transmission fluid level.
  9. Drive the vehicle for fifteen minutes making sure to select all the gears manually.
  10. Repeat the procedure once the transmission warm-up, but this time, the level must be between the MIN and MAX marks for the HOD (higher) markings.

Not all Jeep vehicles have a transmission dipstick. If the dipstick is not present, the vehicle will need to be raised on a lift, and the level can be checked via the fill hole.

Reset Automatic Transmission Adaptation

Reset Jeep Transmission Adaptation

Adaptive automatic transmission monitors your driving behavior and adjusts the gear shits to deliver the driver’s best engine response and shift points.

If you have a newer Jeep, it is highly likely to monitor your driving behavior. Resetting the transmission adaptation to the factory setting can make your Jeep shift normal again. This simple procedure can improve shifting and does not cause adverse effects.

This procedure will work on W5A580 transmission but may also work on other models. It does not cause any problems and doesn’t hurt to try.

Here is how to reset the Jeep transmission without any tools:

  1. Press the gas pedal down and keep it pressed.
  2. Turn the ignition on without starting the engine.
  3. Keep the ignition on (engine off), and the gas pedal pressed for thirty seconds.
  4. Turn the ignition off.
  5. Release the gas pedal.

Start the engine, and don’t drive too aggressively for the next twenty miles. If the procedure above does not improve the shift quality, you can perform a transmission adaption reset with a professional scanner.

Read Transmission Fault Codes

reset jeep transmssion

If the transmission fluid level is correct, the next step is to read fault codes from the transmission control module, or what is known as the TCU. To retrieve transmission codes, you will need a Jeep OBD-II Scanner. Basic code readers are not recommended because they can only read codes from the Engine Control Unit and not Transmission Control Unit.

  1. Park the vehicle and turn off the ignition—set parking brakes.
  2. Locate the diagnostic port under the dashboard, driver’s side.
  3. Plugin your OBD-II scanner, then turn on the ignition without starting the engine.
  4. The scanner will turn on. Allow it to communicate with the vehicle. Select MAKINA; then, your particular model.
  5. Select Control Units, then Transmission.
  6. Select Read Fault Codes from the main menu.

Check For Recalls

Lastly, always check if any open recalls or Technical Service Bulletin (TSB) exist for your Jeep. Recalls are performed free of charge by any Jeep dealer. Visit our Check Recalls page to check if a recall exists on your vehicle.

Ask if Technical Service Bulletins (TSB) also exist for your car. TSBs for the transmission typically update the Engine or Transmsimon control unit software. TSBs can program the shift solenoids, which makes the transmission shift better.

We hope you find the Troubleshooting Jeep Transmission Problems guide helpful. Check these troubleshooting and repair guides for more help on your Jeep.

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