6L80 vs 722.6: Differences and Which One to Choose

These two automatics end up on the same shopping list more often than you would think. A Chrysler 300C, Charger, Challenger or Jeep Grand Cherokee owner shopping a NAG1 rebuild starts cross-shopping a 6L80 out of a Silverado for a swap. A GM truck owner researching a European conversion runs into the 722.6 from the other direction. And both units land in the same LS-swap and hot-rod conversations, because the 722.6 was the transmission Mercedes bolted behind the SLR McLaren and the SL65, while the 6L80 was the transmission GM bolted behind LS and LT V8s for nearly two decades.

They are not interchangeable, they do not fail the same way, and they do not cost the same to keep alive. Here is the real comparison, with numbers from the factory and from the rebuild-industry sources that see these units on the bench every week.

The short answer

If you are running a domestic V8 in a truck, SUV or rear-drive muscle car and you want the widest gear spread, the deepest parts supply and the lowest per-repair cost, the 6L80 is the choice. If you own a Mercedes, a Chrysler LX-platform car, a Jeep WK, a Sprinter, a Crossfire or a Jaguar that already came with the 722.6, keeping and rebuilding that unit is almost always the smarter move than swapping. The 722.6 is a genuinely strong gearbox, and the swap costs (driveshaft, crossmember, wiring, controller, shifter, converter) eat any theoretical gain.

6L80: what it actually is

The GM 6L80 is a longitudinal, six-speed, rear-wheel-drive automatic built from the 2005 through 2023 model years. Per Wikipedia's GM 6L transmission entry, the ratio set is 4.027 / 2.364 / 1.532 / 1.152 / 0.852 / 0.667 with a 3.064 reverse, giving a total ratio span of 6.040. That same source lists maximum input torque figures of 800 Nm (590 lb-ft) and 1,200 Nm (885 lb-ft) depending on the build, and describes the 6L90 as "a strengthened and uprated version of the 6L 80, used primarily in heavy-duty truck/van applications."

In service terms, the 6L80 is a Dexron VI unit with a cast-aluminum case, a torque converter clutch that can lock in all six forward gears, and, critically for diagnosis, a TEHCM (transmission electro-hydraulic control module) that lives inside the pan and carries the solenoids as one assembly. If you have not worked on one before, that single design decision drives most of what makes the 6L80 different to service than a 4L60E.

722.6: what it actually is

The Mercedes 722.6, sold as 5G-Tronic and badged NAG1 in Chrysler products, is a five-speed rear-drive automatic produced from 1996 to 2020. Wikipedia's 5G-Tronic entry confirms it is an "electronically shifted 5-speed overdrive automatic transmission with torque converter lock-up, typically in gears 3, 4 and 5."

The key thing to understand is that "722.6" is a family, not a single part. The W5A designation encodes the maximum input torque in newton-meters. Per that same source: W5A280 (280 Nm / 207 lb-ft, vans including Vito, Sprinter and Vario), W5A300 (300 Nm / 221 lb-ft), W5A330 (330 Nm / 243 lb-ft, four-, five- and six-cylinder passenger cars), W5A400 (400 Nm / 295 lb-ft, eight-cylinder SUVs), W5A580 (580 Nm / 428 lb-ft, eight- and twelve-cylinder passenger cars) and W5A900 (up to 1,000 Nm / 738 lb-ft).

Transmission Digest adds the U.S.-market detail: "In the U.S., NAG1 units include the W5A580, W5A380, W5A330 and W5J400... J400 identifies the unit as a Jeep application." That article also gives you a free identification trick worth memorizing: "If the unit has only a pin stamp on the driver side, or a combination pin stamp and bar-code tag, it was manufactured in Germany. If it has only a bar-code tag, it was manufactured by Chrysler."

Fluid is not one-size-fits-all either. Per Transmission Digest, "The Sprinter, Crossfire and Mercedes units require specific fluid because of calibration issues; the other Chrysler applications use ATF4." Do not assume ATF+4 covers your car just because the badge on the trunk says Chrysler.

Head to head: the numbers that matter

Gear count and spread

The 6L80 wins outright: six ratios spanning 6.040 against the 722.6's five. Per Transmission Digest, the W5A330 has the widest gear ratio spread of the 722.6 family, with the other variants sharing a common ratio set. A 6.04 span means a deeper first gear for launch and a taller sixth for cruising out of the same box, which is exactly the advantage a six-speed is supposed to deliver over a five.

Torque capacity

This is closer than the badges suggest. A standard 6L80 at 800 Nm (590 lb-ft) input sits between the W5A580 (428 lb-ft) and the top-tier W5A900 (738 lb-ft). If you are comparing a truck 6L80 against a W5A580 out of a Chrysler 300C SRT8 or an S-Class, the GM unit carries the higher factory rating. If you are comparing against a W5A900, the Mercedes unit has more headroom, but W5A900 units were never a volume part and are not a realistic core to go shopping for.

Control strategy

The 722.6 is genuinely clever for a mid-1990s design. Per the Ultimate-NAG52 technical wiki, the unit "consists of 3 pressure solenoids, 3 solenoids, 3 clutches and 2 brakes," with an additional brake used only in reverse. The MPC (modulating pressure control) solenoid sets main line pressure, the SPC (shift pressure control) solenoid manages the engaging clutch during a shift, and the Y3/Y4/Y5 on-off shift solenoids command the actual gear change. Both MPC and SPC run 1000 Hz PWM.

That same source documents a failsafe worth knowing before you condemn a unit: "In the event the TCU was to actuate a shift solenoid out of order... the gearbox will automatically go into Neutral. This is a hydralically commanded Neutral engagement and the TCU can only regain control of the gearbox once the car has been turned off to drain any pressure in the gearbox." A 722.6 that drops to neutral and stays there until a key cycle is not automatically a mechanically dead transmission.

How each one fails, and this is where the money is

The 6L80's signature failure is the converter

Sonnax published a tech advisory specifically on this. Per their 6L80 and 6L90 converter advisory, "the converters in these units are experiencing a high percentage of failure and are more problematic than normal." Most full-size trucks and SUVs use a JMBX full-size (300mm) converter, described as "a single-disc, non-captive clutch unit that is somewhat similar to late 300mm 4L60-E converters," and Sonnax reports that "a high percentage of units show extreme damage due to the clutch piston and front cover crashing into each other."

The failure sequence Sonnax describes is the one every 6L80 shop recognizes: a check engine light, a slipping sensation with intermittent clunks, code P0741 with TCC slip percentage way out of range, and a pan full of debris. On teardown, "the unit is loaded with metal, and the pump (bell housing) is worn to the point of needing remachining or replacement." That metal came from the converter.

The practical lesson: on a 6L80 you do not reuse the converter, and you do not rebuild the unit without following where the contamination went. That means the pump, the valve body bores, and every friction surface.

The 722.6's signature failure is bore wear in the valve body

Transmission Digest describes it precisely: engine-speed flare on a 2-3 or 4-5 upshift, or a neutral flare on a 5-4 or 3-2 downshift. The mechanism is that "the outer bore of the working-pressure regulator valve wears and allows the pMod solenoid-signal oil to leak past the boost end of the valve. As the casting wears, working pressure does not increase with engine load and the flare or loss of gear occurs." Their conclusion on root cause: "We believed that the lack of hardness of the valve-body material was the cause of this common failure." The same article notes that in 1998 many high-mileage cars repaired under Mercedes warranty showed the identical 2-3 flare leading to limp mode.

That is a fundamentally different repair from the GM unit. The 6L80 sends you shopping for a converter and a pump. The 722.6 sends you shopping for valve body repair, a conductor plate, or a reman electro-hydraulic unit.

The 6L80's other well-documented problems

Sonnax's no-movement diagnostic guide for the 6L45/50 and 6L80/90 is one of the more useful free documents in the industry, and it lists causes most people miss:

• Line pressure stuck at roughly 60 to 68 psi with no rise points to a TEHCM line pressure solenoid stuck in exhaust mode. Sonnax notes "unplugged is no different," so an unplug test tells you nothing here.
• A Type 2 separator plate on a Type 1 valve body causes a no-Forward condition. Early Type 1 valve bodies cannot be updated to the later eight-checkball plate; the correct plate, part 24245720, uses seven checkballs. Line pressure reads normal, which is what makes this one so easy to chase in the wrong direction.
• A Type 1 separator plate (24245720) on a Type 2 valve body gives you no third gear and no reverse, again with normal line pressure.
• Clutch select valves or springs installed backwards cause no movement. Per Sonnax, "Valves go in first with springs outboard."
• A 6L90 valve body installed on a 6L80 is a no-Reverse condition. These parts look close enough to get swapped by accident.
• Pressure below 30 psi at idle may be a missing pressure regulator boost valve retaining roll pin.
• The 1-2-3-4 clutch regulator valve stuck gives no Forward, and the 3-5-R clutch regulator valve is also known to stick and cause no Reverse plus shift complaints. Sonnax specifically warns that "the 1-2-3-4 clutch regulator valve issue is usually discovered after the repair/reinstall," meaning after the transmission is already back in the truck.
• A TEHCM with the wrong part number or programming causes no movement or no upshift. Always verify the part number and program file match the VIN.

One more from that guide that saves an unnecessary teardown: during OE programming or a relearn, a temporary no-move condition can occur. Sonnax's fix is to "remove scanner, key from ignition, then open/close driver door. Wait 15 to 20 minutes and return; it's usually good to go."

Which one should you choose?

Choose the 6L80 if

• You are already in a GM truck, SUV, Camaro, Corvette, G8 or SS. The 6L80 replaced the 4L60E across most large V8 applications beginning with the 2006 model year.
• You want six ratios and a 6.04 spread rather than five ratios.
• You want the broadest parts availability. GM built these in enormous volume across eighteen model years, and the aftermarket supports them heavily.
• You are doing an LS or LT swap where GM controller integration matters.

Choose the 722.6 if

• Your vehicle already has one. This is the big one. A Grand Cherokee WK, a Chrysler 300, a Charger, a Magnum, a Crossfire, a Sprinter, a Jaguar or any 1996 to 2020 rear-drive Mercedes is engineered around this unit, and replacing it with anything else means a new crossmember, driveshaft, wiring, controller and shifter linkage.
• You need a compact five-speed behind a high-torque engine and can source a W5A580 or better. Mercedes used this family behind the SL65 and the SLR McLaren, so the design ceiling is real.
• You value the shift quality. The load-sensitive working pressure and overlap clutch control that Transmission Digest describes were advanced for the era, and the unit still shifts smoothly when the valve body is healthy.

The repair reality: what each rebuild involves

6L80 rebuild scope. Frictions and steels, all seals and gaskets, a new or properly remanufactured converter (not the original, per the Sonnax advisory above), pump inspection and likely remachining if the converter came apart, and valve body attention. Because the TEHCM lives in the pan with the solenoids, a solenoid problem and a control module problem are the same physical assembly, which simplifies parts ordering but raises the floor on a solenoid-only fix. A 6L80 overhaul kit covers the soft parts, a 6L80E shift solenoid kit handles the electrical side, and if bore wear or a mismatched separator plate is your problem, a complete 6L80 valve body with solenoids sidesteps that diagnosis entirely.

722.6 rebuild scope. Frictions, steels, seals, the pan filter, the conductor plate and its adapter seals, and, given what Transmission Digest documented about bore wear, serious inspection of the working-pressure regulator valve bore. Fluid choice matters more here than on the GM unit. A 722.6 master rebuild kit covers the internals, and a 722.6 six-piece shift solenoid kit addresses the MPC, SPC and Y3/Y4/Y5 solenoids as a set, which is the right approach since they age together.

Replace while you are in there

On either unit, the cost of going back in is far higher than the cost of the part. On a 6L80: torque converter (mandatory if there was any metal in the pan), pan filter, TEHCM filter and its gasket — Sonnax notes that leaving the TEHCM filter gasket out during assembly "will cause no movement" — pan gasket, bushings, and the valve body checkballs, since per that same guide the No. 1 checkball shrinking and moving out of place causes no Forward and the No. 5 checkball out of place causes no Reverse. On a 722.6: conductor plate, speed sensors, the adapter plug and its O-rings, pan filter, pan gasket, and the torque converter, which on this unit is a multi-disc lockup design.

Browse the full transmission rebuild kits and shift solenoid kits collections to match parts to your unit by model and year.

Cost and effort framing

Neither of these is a first-timer driveway job. Both are longitudinal rear-drive units heavy enough to require a transmission jack, plus exhaust and driveshaft removal and a crossmember drop.

6L80: removal and reinstall commonly runs in the 6 to 9 hour range on a full-size truck, plus bench time for the rebuild itself. Difficulty is moderate for anyone who has done a 4L60E, with the important caveat that TEHCM programming to the VIN requires a capable scan tool. A used module pulled from another truck will not simply work.

722.6: removal and reinstall runs similar hours, but the electronic side is far less forgiving. Conductor plate work, adapter sleeve sealing and the fluid-specification issue mean this one rewards either factory-level tooling or a shop that sees NAG1 units regularly. The hydraulic failsafe neutral behavior also means self-diagnosis can send you in the wrong direction.

FAQ

Can I swap a 6L80 into a car that came with a 722.6?

Physically it has been done, but it is a full custom project, not a bolt-in. Different bellhousing pattern, different length, different crossmember location, different driveshaft, different shifter and a completely different control system. The GM unit needs GM controller logic. On a Chrysler LX or Jeep WK you would be re-engineering the entire driveline to gain one ratio. Rebuilding the 722.6 you already have is nearly always the cheaper path.

Is the 722.6 actually stronger than the 6L80?

It depends entirely on which 722.6. A W5A330 at 243 lb-ft is well below a standard 6L80's 590 lb-ft rating. A W5A580 at 428 lb-ft is still below it. Only the W5A900, rated to 738 lb-ft, exceeds a base 6L80, and if you need more than a base 6L80, GM's own answer was the 6L90, which Wikipedia describes as the strengthened, uprated version built for heavy-duty truck and van use.

My 6L80 has code P0741 and feels like it is slipping. Is the transmission gone?

P0741 with high TCC slip is the exact pattern Sonnax describes as the leading edge of a JMBX converter failure. Drop the pan and look. If you find metal or debris, the converter is the likely source and the contamination has already reached the pump and valve body, which means a full teardown rather than a converter-only replacement. If the pan is clean, the fault may be in the TCC control circuit instead. Sonnax notes that the pump TCC control valve, depending on the position it sticks in, can cause shudder during TCC apply or when coasting to a stop.

Sources

• GM 6L transmission — Wikipedia (6L80 gear ratios, ratio span, input torque ratings, production years, 6L90 relationship)
• Mercedes-Benz 5G-Tronic transmission — Wikipedia (W5A variant torque ratings, production years, applications, torque converter lock-up behavior)
• Mercedes 722.6, Daimler W5, Porsche W5, Jaguar 722.6 — Transmission Digest (NAG1 designations, German vs Chrysler identification, fluid requirements, working-pressure regulator bore wear)
• 6L80, 6L90 Transmission Tech Advisory: Consider an Updated Converter in Your Next Rebuild — Sonnax (JMBX converter failure pattern, P0741, contamination path, pump damage)
• GM 6L45/50, 6L80/90 No Movement Conditions: Analysis and Repair Tips — Sonnax (separator plate 24245720, line pressure values, clutch regulator valves, checkball positions, TEHCM programming)
• 722.6 Info — Ultimate-NAG52 wiki (solenoid architecture, MPC/SPC/TCC control, hydraulic failsafe neutral behavior)

Related reading: 6L80 vs 6L90: differences, strength and parts interchange and 722.6 valve body symptoms: how to know yours is failing.