Jeep JK/JL Wrangler Transmission Service Guide: Every Trans, Every Fluid, Every Interval

The Jeep Wrangler has shipped with five different transmissions across the JK (2007-2018) and JL (2018-present) generations. If you work on Jeeps or own one, you need to know which transmission is in front of you before you pull a drain plug, because the fluid specs, capacities, and service procedures are completely different between them. Using the wrong fluid in a Wrangler transmission is one of the most common mistakes I see, and it causes real damage.

This guide covers every transmission that went into the JK and JL Wrangler: the NSG370 manual, the W5A580 (Mercedes-sourced 5-speed auto), the 42RLE automatic, the 845RE and 850RE (ZF 8- and 9-speed autos), and the manual options on the JL. Real fluid specs, real capacities, real failure patterns.

See all Jeep transmission guides, service resources, and tools on our Jeep hub page.

---

Quick Reference: Which Transmission Is in Your Wrangler

Before anything else, identify what you are working on. Here is the breakdown by year and engine:

• 2007-2011 JK, 3.8L V6, automatic: 42RLE (4-speed)
• 2007-2011 JK, 3.8L V6, manual: NSG370 (6-speed)
• 2012-2018 JK, 3.6L V6, automatic: W5A580 (5-speed, Mercedes NAG1)
• 2012-2018 JK, 3.6L V6, manual: NSG370 (6-speed)
• 2018-present JL, 3.6L V6, automatic: 850RE (ZF-based 8-speed)
• 2018-present JL, 2.0L turbo, automatic: 845RE (ZF-based 8-speed)
• 2018-present JL, 3.6L V6, manual: NSG370 (6-speed, carryover)
• 2024-present JL 392/Rubicon, automatic: 8HP75 (ZF 8-speed, heavy-duty variant)

The RPO code on the door sticker or the 8th digit of the VIN (engine code) combined with the transmission indicator will tell you exactly what you have. If you are doing phone diagnosis or quoting a job, always ask the customer for the VIN. Do not guess based on year alone -- the 2018 model year is a split year where both JK and JL were sold simultaneously.

---

NSG370 Manual Transmission (JK and JL)

Overview

The NSG370 is a 6-speed manual built by Mercedes (later produced under the FCA umbrella) that Jeep used across the entire JK generation and carried forward into the JL. It is a reasonably strong unit for the 3.6L and 3.8L applications, though it has specific weak points that show up at higher mileage and especially on lifted Wranglers with oversized tires.

Fluid Specification and Capacity

The NSG370 requires Mopar Manual Transmission Lubricant (PN 68218925AA) or equivalent meeting the MS-9224 specification. This is a synthetic 75W-85 GL-4 fluid. Do not use GL-5 gear oil in the NSG370. The GL-5 extreme-pressure additives attack the brass synchronizer rings in this transmission. I have personally seen NSG370 units with chewed synchronizers that traced directly back to someone filling it with 75W-90 GL-5 because that is what they had on the shelf.

Capacity: approximately 1.6 quarts (1.5 liters). It does not hold much fluid, which means degraded fluid affects this transmission faster than a unit with 4 or 5 quarts of capacity.

Drain and Fill Procedure

The NSG370 has a drain plug on the bottom of the case (10mm hex) and a fill plug on the driver's side of the case (10mm hex). Drain, let it drip for 10 minutes, reinstall the drain plug and torque to 25 ft-lbs. Fill through the fill plug until fluid runs out level with the fill hole. Torque the fill plug to 25 ft-lbs. That is the entire procedure.

Service Interval

Mopar says 60,000 miles under normal conditions. For Wranglers that see trail use, mud, water crossings, or run 35-inch or larger tires on the street, service at 30,000 miles. The added driveline stress from oversized tires accelerates fluid breakdown.

Common NSG370 Failures

• 1st-to-2nd gear grind: The most reported NSG370 complaint. The 1st-2nd synchronizer wears faster than the others because of the RPM drop required for that shift. Fresh fluid helps. Once the synchronizer brass is gone, it needs replacement -- there is no fluid fix for worn synchros.
• 5th gear pop-out: Typically caused by a worn 5th gear detent spring or detent ball. The spring weakens over time and no longer holds the shift rail in position under load. This is a known issue on higher-mileage NSG370 units.
• Input shaft bearing noise: A whine in neutral that goes away when you push the clutch in. The input shaft bearing (PN 68002270AA) wears, especially on units that spend a lot of time idling in neutral at traffic lights or trail obstacles.

---

42RLE Automatic (2007-2011 JK)

Overview

The 42RLE is a 4-speed automatic that Chrysler used in the 3.8L JK Wrangler, plus the Liberty, Nitro, and some Chrysler sedans. It is an adequate transmission for stock applications but was always on the edge of its torque capacity with the 3.8L in a vehicle as heavy as the Wrangler. Adding larger tires and a lift pushed many 42RLE units past their limits.

Fluid Specification and Capacity

The 42RLE requires ATF+4 (Mopar PN 68218058AC). No substitutes. ATF+4 is not a marketing name, it is Chrysler Material Standard MS-9602, and a licensed fluid carries that approval on its data sheet — Mobil's ATF+4 product data sheet, for example, lists "Chrysler MS-9602" under approvals and states the product is for Chrysler, Dodge, Plymouth, Eagle and certain Jeep automatic transmissions requiring a fluid meeting the ATF+4 specification. The same sheet says outright that the fluid is not recommended for vehicles requiring Ford Mercon or GM Dexron type fluids, which is the other half of the point: Dexron III, Dexron VI or Mercon in a 42RLE will give you TCC shudder and shift quality problems.

Total capacity: approximately 8.5 quarts. A pan drop and filter change recovers about 4.5-5 quarts. The torque converter holds the rest.

Service Interval and Procedure

Service every 30,000 miles for any JK that sees trail use or tows. Every 60,000 miles minimum for street-only driving. The 42RLE has a spin-on external filter (Mopar PN 52108325AA) located on the driver's side of the transmission, plus an internal filter accessible through the pan. At each service, replace both the external spin-on filter and the internal filter/gasket. Drain plug torque: 20 ft-lbs. Pan bolt torque: 105 in-lbs (not ft-lbs -- this is a common overtightening mistake that warps the pan).

Common 42RLE Failures

• Solenoid pack failure: The 42RLE solenoid pack (PN 52854001AA) is the most common failure point. Symptoms include harsh 2-3 shift, delayed engagement, or limp mode. The solenoid pack is a single unit that bolts to the valve body -- individual solenoids are not replaceable separately.
• Overdrive clutch pack burnout: The OD clutch pack is the weak link when the 42RLE is under sustained load (highway towing, large tires at highway speed). Burnt fluid and a P0734 or P0735 code usually mean the OD clutches are gone.
• Valve body wear: The pressure regulator valve bore in the 42RLE valve body wears over time, causing erratic line pressure. Sonnax's published 42RLE catalog splits the fix by valve body type: 92835-24 is the oversized pressure regulator valve for non-VLP units, listed against shift concerns, low line pressure, burnt clutches and poor lube oil control, and 92835-29 is the VLP version, listed against shift concerns, low and high line pressure, erratic TCC apply and poor lube oil control. Identify which valve body you have before ordering — the two valves are not interchangeable.

---

W5A580 Automatic (2012-2018 JK)

Overview

When Jeep moved to the 3.6L Pentastar V6 in the 2012 JK, the 42RLE was replaced with the W5A580, which is the Mercedes NAG1 5-speed automatic built under license. This is the same basic transmission found in 300C, Charger, Grand Cherokee, and various Mercedes-Benz applications. It is substantially stronger than the 42RLE and handles the 3.6L's 285 lb-ft without issue in most applications.

Fluid Specification and Capacity

The W5A580 requires ATF+4 (Mopar PN 68218058AC). Same fluid as the 42RLE -- different transmission, same fluid spec. Chrysler/FCA specified ATF+4 for the W5A580 across all their applications. Total capacity is approximately 9.5 quarts. A pan service recovers about 5 quarts.

Service Interval and Procedure

Same recommendation as the 42RLE: 30,000 miles for trail or towing use, 60,000 miles for street-only. The W5A580 uses an internal filter (Mopar PN 5189966AB) accessed through the transmission pan. The pan uses a reusable molded gasket -- inspect it for damage and reuse if it is in good shape. Pan bolt torque: 70 in-lbs. The fill procedure on the W5A580 requires checking fluid level at operating temperature (180-200F) through the overflow tube or via a scan tool reading transmission temperature. Overfilling the W5A580 causes foaming and erratic shift behavior.

Common W5A580 Failures

• Torque converter shudder: TCC shudder on the W5A580 is often fluid-related. A fluid exchange with fresh ATF+4 resolves many shudder complaints. If shudder returns after a fluid change, the converter lockup clutch is damaged and the converter needs replacement.
• Valve body conductor plate failure: The conductor plate (PN 52108308AC) carries the speed sensors and the electrical connections for the solenoids. A failed conductor plate causes erratic shifting, multiple solenoid codes, and sometimes a no-shift condition. It is a common repair on higher-mileage W5A580 units.
• Output speed sensor failure: Causes erratic speedometer readings and shift timing problems. The sensor (PN 56041393AB) is external and replaceable without dropping the pan.

For more on ATF+4 and how it compares to other automatic transmission fluids, see our complete ATF fluid types guide.

---

845RE and 850RE Automatic (2018-Present JL)

Overview

The JL Wrangler moved to ZF-based 8-speed automatics. The 845RE pairs with the 2.0L turbocharged four-cylinder (eTorque mild hybrid), and the 850RE pairs with the 3.6L Pentastar V6. Both are variants of the ZF 8HP architecture -- the same family that ZF supplies to BMW, Audi, Jaguar Land Rover, and others. These are genuinely good transmissions with fast, smooth shifts and a wide ratio spread that improves both off-road crawl capability and highway fuel economy compared to the old 5-speed.

Fluid Specification and Capacity

Both the 845RE and 850RE require ZF LifeguardFluid 8 (Mopar PN 68218925AB) or equivalent meeting the ZF S671.090.312 specification. ZF is unambiguous about this in its own product data sheet: LifeguardFluid 8 was developed specifically for the 8HP family, and only ZF LifeguardFluid 8 or LifeguardFluid 9 may be used in those transmissions. This is NOT ATF+4. This is a different fluid with different viscosity and friction characteristics designed specifically for the ZF 8HP valve body and clutch pack geometry. Putting ATF+4 in an 845RE or 850RE will cause shift quality problems and potentially damage the mechatronic unit.

Total capacity: approximately 9.0 quarts for the 850RE, 8.5 quarts for the 845RE. A pan drop recovers about 4.5-5 quarts. The remainder is in the torque converter and cooler lines.

Service Interval and Procedure

FCA says "lifetime fill" on the JL automatics. ZF itself does not take that position on its own hardware: while its 5-, 6-, 8- and 9-speed automatics are factory filled maintenance-free, ZF recommends an oil change after 150,000 km (about 93,000 miles) because of the many factors that affect transmission life in real service. Treat "lifetime" as a warranty-period claim, not an engineering one. Service at 60,000 miles for normal driving, 30,000-40,000 miles for trail use, towing, or heavy stop-and-go. The ZF 8HP architecture benefits enormously from regular fluid changes because the mechatronic unit (integrated valve body and TCM) is sensitive to contaminated fluid.

The drain and fill procedure on the 850RE uses a drain plug on the pan and a fill tube on the passenger side of the case. Fluid level must be checked at operating temperature (185-195F) using a scan tool to read trans temp. The overflow method works: fill until fluid runs from the check plug at operating temperature. Pan bolt torque: 70 in-lbs. Drain plug torque: 12 ft-lbs (the drain plug is aluminum on some applications -- do not overtighten).

The internal filter (Mopar PN 68233701AA) should be replaced at each service. The pan gasket is integrated into the pan on some model years -- check whether your application has a separate gasket or a pan with molded seal.

Common 845RE/850RE Failures

• Mechatronic unit failure: The mechatronic unit integrates the valve body, solenoids, and TCM into a single assembly. When it fails, symptoms range from harsh shifting to complete loss of gear engagement. Replacement is expensive -- typically $2,500-$4,000 for the part alone. Keeping the fluid clean is the single best preventive measure.
• Torque converter shudder at low speed: A known complaint on early 2018-2019 JL units. FCA issued TSB 21-019-20 REV.A addressing this with a software reflash and fluid change. If you encounter this on a 2018-2019 JL, check whether the reflash has been performed.
• Delayed engagement from cold: Some JL owners report a 1-2 second delay when shifting from Park to Drive or Reverse when cold. In many cases this is normal operating behavior for the ZF 8HP -- the mechatronic unit takes a moment to build line pressure from a cold start. If the delay exceeds 3 seconds or is accompanied by a harsh engagement, inspect the fluid level and condition.

---

Wrangler-Specific Service Considerations

Lifted Wranglers and Oversized Tires

This is where most Wrangler transmission problems originate. A stock JK or JL with 32-inch tires and no lift puts a certain load on the transmission. A JK with a 4-inch lift, 37-inch tires, 4.56 regear, and steel bumpers puts a fundamentally different load on the same transmission. The transmission was not designed for that load profile.

If you are building or servicing a modified Wrangler, the transmission service interval should be cut in half from stock recommendations. A JK W5A580 on 37s should be serviced every 30,000 miles maximum. A JL 850RE on 35s with regular trail use should see fresh fluid every 25,000-30,000 miles. The additional rotating mass of larger tires creates more heat in the torque converter, which degrades fluid faster.

Water Crossings

Wranglers cross water. That is what they are for. But transmission cases are not sealed -- they have vent tubes that equalize pressure as the unit heats and cools. When the transmission is submerged in water, water enters through the vent. A small amount of water in ATF causes rapid fluid degradation, clutch material swelling, and bearing corrosion. After any water crossing where the transmission case was submerged, do a fluid service within the next 500 miles. Do not wait for symptoms. By the time you have symptoms from water contamination, you have internal damage.

Transfer Case Interaction

Wrangler owners sometimes report transmission symptoms that are actually transfer case problems. The NV241 (JK) and MP3022 (JL) transfer cases share fluid circuits with the transmission on some configurations. Before diagnosing a transmission issue, verify the transfer case fluid level and condition. The NV241 uses ATF+4. The MP3022 uses a specific Mopar transfer case fluid (PN 68218655AB). Mixing these up causes problems in the transfer case that can present as transmission symptoms.

Transmission Cooler Upgrades

The factory transmission cooler on both the JK and JL is adequate for stock applications in moderate climates. It is not adequate for a built Wrangler running 35-inch or larger tires in summer heat, especially on highway drives to and from the trail. An aftermarket transmission cooler (Hayden 679 or Derale 13502 are common fits) installed in-line with the factory cooler drops fluid temperatures by 20-40F under load. The installation is straightforward: tap into the factory cooler lines at the radiator, run them through the auxiliary cooler, and route them back. Use AN fittings and braided line if you want reliability off-road -- rubber cooler hose gets snagged on rocks and trail debris.

Monitor your transmission temperature with a scan tool or dedicated gauge. The 42RLE and W5A580 should operate at 180-220F under normal conditions. Sustained temps above 240F accelerate fluid breakdown. The 850RE runs slightly cooler by design (170-200F normal range) but is more sensitive to temperature spikes because of the mechatronic unit.

---

Fluid Quick Reference Table

For quick reference when a Wrangler rolls in and you need to pull the right fluid off the shelf:

• NSG370 (manual, all years): Mopar MS-9224 synthetic 75W-85 GL-4 -- 1.6 quarts
• 42RLE (2007-2011 JK auto): ATF+4 -- 8.5 quarts total, ~5 quarts pan service
• W5A580 (2012-2018 JK auto): ATF+4 -- 9.5 quarts total, ~5 quarts pan service
• 845RE (2018+ JL 2.0T auto): ZF Lifeguard 8 -- 8.5 quarts total, ~4.5 quarts pan service
• 850RE (2018+ JL 3.6L auto): ZF Lifeguard 8 -- 9.0 quarts total, ~5 quarts pan service
• NV241 transfer case (JK): ATF+4
• MP3022 transfer case (JL): Mopar transfer case fluid PN 68218655AB

Print this out and tape it to the wall next to your fluid rack. The number one mistake on Wrangler transmission services is pulling the wrong fluid because someone assumed all Jeeps take ATF+4. They do not.

---

Diagnostic Codes by Transmission

When a Wrangler comes in with a check engine light and transmission symptoms, the codes you see depend entirely on which transmission is in the vehicle. Here are the most common codes by unit:

42RLE Common Codes

• P0750: Shift solenoid A malfunction -- solenoid pack failure, most common 42RLE code
• P0755: Shift solenoid B malfunction -- same solenoid pack, same root cause
• P0734/P0735: Gear ratio error 4th/5th -- overdrive clutch pack wear or solenoid issues
• P0740: TCC circuit malfunction -- check the solenoid pack and fluid condition first

W5A580 Common Codes

• P0715: Input speed sensor circuit -- often the conductor plate, not the sensor itself
• P0720: Output speed sensor -- external sensor replacement, straightforward fix
• P0741: TCC performance -- fluid service first, then evaluate the converter
• P0868: Transmission fluid pressure low -- check fluid level, then evaluate the pressure regulator

845RE/850RE Common Codes

• P0730: Incorrect gear ratio -- often a mechatronic unit issue on higher-mileage JL units
• P0741: TCC performance -- fluid service and TSB reflash check for 2018-2019 models
• P0876: Transmission fluid pressure sensor -- mechatronic unit internal sensor
• U0101: Lost communication with TCM -- wiring issue to the mechatronic unit or the unit itself

---

Recommended Products

---

Internal Links and Related Reading

• Jeep Transmission Hub Page -- all Jeep guides, service resources, and courses
• Complete ATF Fluid Types Guide -- ATF+4 vs. Mercon LV vs. Dexron VI and when each applies
• Flush vs. Drain and Fill -- which method to use and when
• Torque Converter Clutch Shudder Diagnosis -- applies directly to W5A580 and 850RE shudder complaints
• How to Read Transmission Live Data -- essential for ZF 8-speed fill procedures
• Best Scan Tools for Transmission Shops in 2026