42RE Transmission Issues: Common Problems and Solutions
The 42RE automatic transmission found in many Jeep Grand Cherokees and Jeep Wranglers is generally quite reliable. However, like any complex mechanical system, the 42RE can develop issues over time that require troubleshooting and repair. In this article, we’ll explore some of the most common 42RE transmission problems Jeep owners face, steps for diagnosing issues, and potential solutions.
Table of Contents
What Causes 42RE Transmission Problems in Jeeps?
The 42RE four-speed automatic overdrive transmission was used in Jeep Grand Cherokees from 1993-2004 and Jeep Libertys from 2002-2004. Some key components and mechanisms within the 42RE that can develop problems include:
Sensors
The transmission speed sensor, output speed sensor, throttle position sensor, and other sensors provide key data inputs to the transmission control module and the engine control module. Faulty sensors can cause shifting problems.
Solenoids and switches
Shift solenoids, pressure control solenoids, pressure switches, and other solenoids control hydraulic pressure and gear engagement. Failed solenoids or switches will affect shifting.
Valve body
The valve body houses many small valves that route hydraulic fluid to clutches and bands to control shifting. Contaminants or wear can cause valve body problems.
Torque converter
The torque converter can fail to lockup properly due to issues with the torque converter clutch solenoids or valves or due to mechanical damage or wear of the converter itself.
Clutches and bands
Friction clutches and bands actuate to engage each gear. Worn clutches or bands will cause slipping and other problems.
Fluid
- Low fluid level or old, contaminated fluid can cause wear and failure of internal components.
These are some of the core internal components that enable smooth, reliable shifting. When one or more components degrade or fail, 42RE transmission problems arise.
Top 10 Common 42RE Transmission Problems
The 42RE is a four-speed automatic transmission that was used in the 4.0L engines of the Jeep Grand Cherokee from 1993 to 2004 . It is a hydraulically controlled transmission, unlike the electronically controlled 42RH . Many 42RE issues result from wear and tear over high mileage. But faulty parts or improper maintenance can also be to blame. Here are some of the most prevalent 42RE transmission problems Jeep owners report:
1. Harsh Shifting
One of the most common complaints regarding the 42RE is harsh shifting, especially when the transmission shifts from first to second gear. The shift may bang into gear or feel delayed and sluggish. Harsh shifting is often caused by low transmission fluid levels or pressures. But worn engine or transmission mounts or electronic components like sensors, solenoids, or actuators can also contribute to harsh shifts.
2. No Shift Into Overdrive
When the 42RE transmission stops shifting into fourth gear overdrive, it’s typically due to failure of the overdrive solenoid or torque converter clutch solenoid. This causes the converter clutch to remain disengaged. The transmission will drive fine in the lower three gears, but fuel economy suffers without fourth gear.
3. Transmission Slips Out Of Gear
Gear slippage usually indicates internal wear – namely, worn clutches or bands. As friction surfaces lose grip, the transmission will struggle to stay in gear when accelerating. Slippage generally starts in higher gears but can progress to lower gears over time. Low fluid level or pressure can also allow slipping, especially when hot.
4. Delayed Engagement
A pronounced delay or slip when initially taking off from a stop is known as delayed engagement. This usually occurs when shifting into first or second gear but can happen on other shifts too. The problem may stem from low line pressure, worn clutches, or malfunctioning sensors or solenoids. Improperly adjusted bands can also prevent firm engagement.
5. No First Gear
If the transmission doesn’t engage first gear, the most likely culprit is a bad underdrive clutch. This is one of the most labor-intensive repairs, since the transmission must be removed and disassembled to access the underdrive clutch pack. Spending this much doesn’t always make sense for higher-mileage vehicles.
6. No Reverse Gear
Like first gear, reverse gear relies on the underdrive clutch. Worn clutches or low pressure can cause loss of reverse. Check fluid level and line pressure first. But the underdrive clutch components probably need attention if reverse is gone.
7. Transmission Overheating
Excessive heat buildup usually points to slippage and poor internal circulation. Low fluid level is one possibility. But worn parts, incorrect fluid, or blocked cooler lines/passages can also lead to overheating. Transmission temperatures approaching 250°F or higher can start degrading seals, warping parts, and accelerating wear.
8. Transmission Noise In Neutral
Howling, whining, or humming coming from the transmission while it’s in neutral could signal a problem with the transmission pump or torque converter. Worn bearings, damaged gears, inadequate fluid level, or incorrect fluid may be allowing excess noise. Noise while in gear usually originates from worn bearings or planetary gear sets.
9. Check Engine Light
Automatic transmission fault codes often trigger the check engine light. Diagnostic trouble codes (DTCs) pointing to specific sensors, solenoids, or actuators help identify the root cause. But lack of codes doesn’t necessarily mean the transmission is fine. So further diagnosis is still needed to pinpoint mechanical issues.
10. Complete Transmission Failure
In a small percentage of cases, the transmission suffers catastrophic failure where none of the gears work.
This is usually caused by an internal hard part failure – like a shattered gear or damaged shaft – attributed to lack of maintenance, low fluid, or abusive driving.
But electronic failures can also lead to total transmission failure in some situations.
Steps For Diagnosing 42RE Transmission Problems
Diagnosing 42RE issues starts with gathering clues and performing some basic checks:
- Note any trouble codes set for transmission components
- Test fluid level and condition
- Inspect fluid for signs of contamination or debris
- Check transmission pan and cooler lines for leaks
- Verify proper operation of lockup torque converter
- Monitor shift quality over multiple cycles
- Compare engine RPM to vehicle speed in each gear
If basic checks come back normal, monitoring live data like pressure sensor readings, solenoid duty cycle, and shift timing provides additional insight. But intermittent problems can still be tricky to isolate. Here are a few more advanced diagnostic steps:
- Conduct stall speed test in drive to check torque converter
- Perform line pressure test to check pump output
- Check for stored trouble codes after test drives to detect intermittent faults
- Use scopes and graphs to visualize sensor data during test drives
- Test the battery, grounds, and transmission electrical connectors
- Check for trouble codes stored in PCM that don’t trigger check engine light
Thorough troubleshooting and diagnostics help identify the specific internal or external transmission components needing repair.
Solutions For Common 42RE Transmission Problems
Fixing 42RE issues varies case by case based on the specific problem, mileage, maintenance history, and repair costs. Here are some possible repair options to consider:
Adjusting bands, replacing worn seals, solenoids, sensors, and fixing leaks may cure some minor problems. But deeper disassembly is needed to access clutches and hard parts.
Repairing or replacing faulty electronic components and wiring can resolve some electrical issues. But some components may require special tools or procedures to replace.
A faulty valve body can cause multiple shifting issues. Overhauling or replacing the valve body along with new gaskets, sensors, and solenoids often helps.
For major wear or damage, a full rebuild with all new clutches, bands, seals, gaskets, and linings may be warranted if the transmission case remains sound. Costs approach those of a remanufactured transmission.
For failed transmissions with extensive internal damage, installing a professionally rebuilt unit from a reputable shop with a warranty is an option. But inspecting and validating the quality first is a must.
One alternative is swapping in a good used 42RE from a salvage yard. Finding one with acceptable miles and service records takes luck. And some assembly work is still required.
Fluid, Filter, Pan Drop Servicing
Regular fluid and filter changes help maximize transmission life. Periodically dropping the pan to clean the magnet and replace the filter screens out contaminants. Use only approved fluids like ATF+3.
Adjustments And Minor Repairs
Adjusting bands, replacing worn seals, solenoids, sensors, and fixing leaks may cure some minor problems. But deeper disassembly is needed to access clutches and hard parts.
Valve Body Overhaul
A faulty valve body can cause multiple shifting issues. Overhauling or replacing the valve body along with new gaskets, sensors, and solenoids often helps.
Transmission Rebuild
For major wear or damage, a full rebuild with all new clutches, bands, seals, gaskets, and linings may be warranted if the transmission case remains sound. Costs approach those of a remanufactured transmission.
Remanufactured Transmission
For failed transmissions with extensive internal damage, installing a professionally rebuilt unit from a reputable shop with a warranty is an option.
But inspecting and validating the quality first is a must.
Transmission Swap
One alternative is swapping in a good used 42RE from a salvage yard. Finding one with acceptable miles and service records takes luck. And some assembly work is still required.
Best Practices To Avoid 42RE Problems
Preventing problems in the first place or addressing them early is ideal. Here are some key maintenance tips for the 42RE:
- Use only approved fluid and change it regularly
- Drop the transmission pan and change the filter to help remove contaminants
- Address leaks immediately to prevent low fluid and internal damage
- Install an auxiliary transmission cooler if towing or hauling heavy loads
- Follow the manufacturer’s recommended service intervals
- Immediately diagnose any new shifting problems or noises
While high mileage increases the likelihood of issues, proper maintenance and operation makes a big difference in 42RE transmission longevity.
Signs It May Be Time For A Remanufactured 42RE
Though the 42RE is generally reliable, at some point replacement becomes the wisest option. Consider a remanufactured transmission if your 42RE shows multiple symptoms or:
- Has over 175,000 miles of unknown maintenance history
- Exhibits extensive slippage or otherwise fails to properly stay in gear
- Has pronounced bearing noise or hard part damage
- Requires removal for major repairs like clutch replacement
- Is needing its third or fourth rebuild
Installing a verified, professional-quality reman unit can provide that “good as new” performance again.
Conclusion
The 42RE automatic transmission used in Jeep Cherokees and Wranglers with 4.0L engines has proven quite durable when properly maintained. But like any complex mechanical system, problems can and do occur – especially at higher mileages. Harsh shifting, slippage, and electrical gremlins are among the most common complaints. Thorough troubleshooting paired with the right repairs or replacements restores smooth, reliable shifting. With proactive maintenance and early diagnosis of issues, the 42RE should deliver years of dependable service.
