C8 Corvette Transmission: Tremec TR-9080 DCT Explained (Ratios, Fluid, Known Problems)

I have lived with three versions of this gearbox: the one in my Stingray, the one in my two Z06s, and the one in the ZR1 I drive now. From the driver’s seat they feel like the same transmission. Underneath, they are not. The final drive changes, the clutch packs and shafts change, and the fluid rules for track days are different depending on which car and which build date you have. Here is the whole TR-9080 story in one place: ratios, what each variant got, fluid, and the problems GM has actually documented, with where each fix stands today.

What the Tremec TR-9080 is

The TR-9080 is an 8-speed dual-clutch transaxle designed by Tremec for the mid-engine C8. It replaced both the manual and the torque-converter automatic the C7 offered, and the C8 has never had a factory manual. The transmission, the differential and the clutch packs share one fluid supply, one pump, one cooler and one filter.

• Two concentric wet clutches. The outer clutch runs the odd gears (1, 3, 5, 7) with five friction plates. The inner clutch runs the even gears (2, 4, 6, 8) with six plates, the extra plate making up for its smaller diameter, per LSX Magazine’s teardown.
• Torque rating at launch. Tremec’s 2019 release rated the first mLSD and eLSD versions at 800 Nm (590 lb-ft) and 7,500 rpm maximum input speed.
• Shift speed. Tremec quotes shifts in less than 100 milliseconds without interrupting torque.
• Differential. Base cars get a clutch-type mechanical limited slip. The Z51 package adds the electronic limited slip.
• Brain. A standalone transmission control module sits in the rear passenger-side wheel well. A replacement valve body has to be programmed to it with a 22-digit part unique number.
• Where it is built. GM’s St. Catharines plant in Ontario built the DCT under license from the 2022 model year. GM Authority reports that as of calendar 2025, every unit comes straight from Tremec in Michigan.

C8 Corvette gear ratios and final drive by variant

The gearset ratios are the same in every spec sheet I checked, Stingray, Z06 and E-Ray. What changes is the final drive, which is where each variant gets its personality off the line.

First gear is 2.91:1 and eighth gear is 0.33:1. Fourth gear is 0.88:1, so fourth through eighth are all overdrive gears. That tall top end is why a C8 loafs at highway speed.

The Stingray without Z51 runs a 4.89:1 final drive. The Z51 package shortens it to 5.17:1. The Z06 runs a 5.56:1 final drive, which GM Authority calls about seven percent shorter than the Stingray. The overall first-gear column is my own math, first gear times final drive. Both differentials on the Stingray share a 3.55:1 ring and pinion, so the difference is made inside the transaxle.

I could not find a published final drive for the ZR1, ZR1X, 2027 Grand Sport or Grand Sport X in any source I could open today, so I left them out instead of guessing.

What changed for the Z06, E-Ray and ZR1

GM tracks these transmissions by RPO code. GM’s own service articles name three: M1L, M1M and MLH. GM ties M1L to the Stingray, and GM Authority reports the Z06 unit as M1M. Third-party spec sites disagree on which code the E-Ray and ZR1 carry, so check the RPO sticker in your glovebox rather than trusting a chart.

Those ZR1 upgrades make sense when you look at the numbers. CorvSport lists the twin-turbo LT7 at 828 lb-ft, well past the 590 lb-ft Tremec quoted for the launch-spec gearbox in 2019. The Stingray’s LT2 was rated at up to 470 lb-ft with the performance exhaust.

The E-Ray shares the Z06’s 5.56:1 final drive on GM Authority’s spec sheet, and GM’s track guidance groups the MLH unit with the Z06’s: no extra track fluid needed. The E-Ray is gone for 2027, replaced by the Grand Sport X. I could not find a GM document describing transmission changes for the Grand Sport X, the 2027 LS6 cars or the ZR1X, so I am not going to invent any.

C8 DCT fluid: type, capacity and service

The C8 DCT holds about 11 liters, or 11.6 quarts, of fluid, according to LSX Magazine. GM specifies DCTF FFL-4 C8 Corvette transmission fluid, sold by ACDelco under part number 19418016. GM’s TechLink tells technicians to shake the bottle hard before pouring and notes a sealed bottle has a three-year shelf life.

• Filter: external canister filter at 7,500 miles, again at 22,500 miles, then every 22,500 miles. GM covers the first one.
• Fluid: changed at least every three years, with the Fluid Life System reset afterward.
• Warning message: CHANGE TRANSMISSION FLUID SOON gives you about 620 miles (1,000 km) to change fluid and filter.

Costs, the DIY versus dealer decision and the filter procedure are in my C8 transmission fluid and DCT filter guide, so I will not repeat them here.

Track days: the extra two quarts

Early Stingrays need extra fluid before a track day. GM’s 2020 Stingray track-prep TechLink said the DCT must have about two quarts of fluid added before track use, to protect against low pump pressure when fluid gets pushed up the side of the case under load. GM’s documents call the amount two quarts in one place and two liters in another. GM also says it is not required to drain the extra fluid afterward.

The rule depends on your transmission and your case:

• M1L with Z51: add the extra fluid before track use.
• M1L without Z51: GM does not condone tracking it, but says the same addition applies if you do.
• M1M and MLH: no track fill required.
• Any car with a Die 3 case: no track fill required. GM revised the M1L case late in the 2023 model year.

To tell which case you have, look at the front edge of the sump pan from underneath. GM says a Die 3 case has 4 fasteners along that edge and the older Die 2 case has 6. CorvetteBlogger reported the change started at Stingray sequence P5137263 in June 2023.

WRPDRIVE has a short video showing the extra fluid going in through the side fill plug, which is easier to reach than the top plug under the airbox: C8 Corvette gets 2 litres of DCT fluid added through the side filler plug.

Known C8 transmission problems and where each fix stands

These are the issues GM has put in writing, plus the symptom owners report most. Bulletins are applied when a car shows the symptom. They are not open recalls you can schedule ahead of time.

On the shudder reports: a 2025 Stingray owner on CarComplaints described a shudder at about 750 miles, and the dealer blamed riding the brake in traffic after an 18-mile test drive failed to reproduce it. On Canadian Corvette Forums, a 2024 owner described a hesitation on upshifts pulling away from a stop under about 30 km/h with a check engine light, and the car needed a new direct clutch assembly. That lines up with the snap ring bulletin, but only the dealer’s diagnosis can confirm it on your car.

The only DCT-related recall I found is the 2023 emission recall for the TCM software. To see what is open on your car, run the VIN at nhtsa.gov/recalls and ask your dealer to check GM’s system too.

What to do when your C8 DCT acts up

1. Write it down. Photograph any message, note the mileage, speed, gear and temperature.
2. Check the basics. Know where your filter service stands. A maintenance reminder is not a fault.
3. Go to a Chevrolet dealer with your records. Inside the powertrain warranty, a covered failure is GM’s problem to fix, and your service records back up the claim.
4. Name the bulletins. Ask whether the fault matches 23-NA-176, 23-NA-197 or the park lock valve repair.
5. If it needs a flatbed, here is how to get a C8 into neutral with the engine off.

FAQ

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Sources: Tremec TR-9080 release, Chevrolet Z06 release, GM Authority on the Z06 DCT, GM Authority E-Ray specs, Automoblog on the Stingray DCT, SlashGear on Z51 gearing, Paul Tan on ZR1 transmission upgrades, CorvSport ZR1 guide, LSX Magazine TR-9080 teardown, GM TechLink on filter and fluid, GM TechLink on track prep, GM TechLink on the Die 3 case, GM TechLink on park lock valve parts, GM Authority on the 2021 investigation, CarComplaints on recall N212336962, GM Authority on DCT production.