GM 6T40 / 6T45 reliability: years to avoid, problems & recalls

By CarWhere Research · Updated

For GM's 6T40 and 6T45 six-speed automatics, GM service bulletins document two main problems: no-drive or no-start conditions from a damaged fluid pump on 2011–2014 Cruze, Equinox, Terrain, Sonic, Verano, Encore and Trax models, and torque-converter seal leaks on many 2010–2013 models. Recall 20V-668 later covered missing accumulator bolts on GM 6- or 9-speed transmissions in some 2018–2020 models.

GM 6T40 / 6T45 at a glance

GM Hydra-Matic 6T40 and 6T45 six-speed front-wheel-drive automatic: key facts
FactDetail
TypeConventional automatic
Forward speeds6
Built byGeneral Motors (Hydra-Matic)
Used byChevrolet, Buick, GMC
Years in use2010s–2019 in the models covered here (GM bulletins span 2010–2019)
Also known as6T40, 6T45, MH8, MHH, MNH
Transmission-related NHTSA recalls listed1
Warranty extensions / special coverage listed0
Court settlements listed0

What the GM 6T40 / 6T45 is

The 6T40 and 6T45 are GM Hydra-Matic six-speed automatics for front- and all-wheel-drive cars and crossovers. GM service bulletins group them with the related 6T30 and 6T50 and list them in the Chevrolet Cruze, Sonic, Malibu, Equinox, Captiva Sport, Orlando and Trax, the Buick Verano, Encore, Regal and LaCrosse, and the GMC Terrain; a 2019 bulletin lists a 6T40 (RPO MNH) behind the 1.5L turbo in the 2018–2019 Equinox and Malibu and the 1.4L in the Encore.

GM revised the design for the 2012 model year, calling the update Gen 2; its bulletin says all 2013 vehicles it covers use Gen 2 units, while 2012 Cruze and Sonic 1.8L models kept the first design. The best-documented problems are in GM preliminary-information bulletins rather than recalls: a damaged fluid pump that can leave the car with no drive or unable to crank, and fluid leaks at the torque-converter seal.

Which vehicles use the GM 6T40 / 6T45?

Makes, models and model years equipped with the GM 6T40 / 6T45
MakeModelModel yearsNotes
ChevroletEquinox2010–2014; 2018–2019 (1.5L turbo)GM bulletins list 2010–2014 Equinox with the 6T30/6T40/6T45/6T50 family; the 2018–2019 1.5L uses the 6T40 (MNH). Check the RPO code, since fueleconomy.gov also lists V6 Equinox automatics[1][2][3][4]
GMCTerrain2010–2014Listed in GM bulletins PI0950A and PI0324F[1][2]
ChevroletCruze2011–2014Listed in GM bulletins PI0324F and PI0950A; 2012 1.8L models kept the first-design unit[1][5]
ChevroletSonic2012–2014Listed in GM bulletins PI0324F and PI0950A[1][2]
ChevroletTrax2013–2015GM lists the 2015 Trax 1.4L turbo with the 6T40 (RPO MH8 FWD, MHB AWD)[1][6]
BuickEncore2013–2014; 2018–20191.4L turbo; GM lists the 2018–2019 Encore with the 6T40 (MNH). fueleconomy.gov lists only a 6-speed automatic for 2013–2019[1][3][7]
BuickVerano2012–2014Listed in GM bulletins PI0324F and PI0950A; fueleconomy.gov lists only 6-speed automatics through 2017[1][8]
Chevrolet / BuickMalibu, Regal, LaCrosse, Captiva Sport, Orlando2011–2014 (varies by model); 2018–2019 Malibu 1.5LListed in GM 6T-family bulletins (Malibu 2011–2013; Regal and LaCrosse 2011–2014; Captiva Sport and Orlando 2012–2014); the 2013 Regal, LaCrosse and Malibu used the 6T40 (MHH)[1][9][3]

GM 6T40 / 6T45 years to avoid vs. safer years

“Years to avoid” here means the model years with the most documented action — recalls, manufacturer warranty extensions or court settlements — not a prediction about any single vehicle. A car from these years with completed repairs and good records can be a sound buy; one without them deserves a closer look.

Model years with the most documented problems

  • 2011–2013 Cruze, Equinox and Terrain (6T-family automatic) — These years appear in both GM's fluid-pump bulletin PI0324F and its torque-converter seal-leak bulletin PI0950A.[1][2]
  • 2012–2014 Sonic and Verano, 2013–2014 Encore and Trax — Listed in GM bulletin PI0324F for no-drive and no-start conditions caused by a damaged fluid pump.[1]

Known GM 6T40 / 6T45 problems

No drive, no crank or no start from a damaged fluid pump (2011–2014)

GM bulletin PI0324F lists vehicles that will not move, engines that crank but will not start or will not crank, fluid leaks, harsh shifts and slipping or missing gears, often at low mileage (frequently under 10,000 miles). GM says these conditions may be caused by no or low line pressure from a damaged transmission fluid pump, and tells technicians to run a line-pressure check before replacing the control-solenoid valve assembly or valve body.[1][10]

Reported symptoms

  • Vehicle will not move in Drive or Reverse
  • Engine cranks but will not start, or will not crank (clicking)
  • Harsh shifts, slipping or missing gears
  • Warning lights such as SES, battery or reduced power

Fluid leak at the torque-converter seal (2008–2013)

GM bulletin PI0950A covers fluid leaking from the torque-converter housing and seal on 6T-family vehicles built before February 1, 2013, including the 2010–2013 Equinox and Terrain, 2011–2013 Cruze and 2012–2013 Sonic and Verano. GM says a torque-converter seal made from a more robust sealing material is now available and should be installed if the old seal is found leaking.[2]

Reported symptoms

  • Transmission fluid drips between the engine and transmission
  • Low transmission fluid level

Snap ring could come out of its groove (2013 inventory vehicles) (2013)

GM service update 13282A had dealers replace the transmission in certain unsold 2013 Regal, LaCrosse and Malibu models with the 6T40 (MHH) before delivery, because an improperly made snap ring could stick to the housing and come out of its groove, turning on the check-engine light and putting the transmission in a default mode. The update applied to inventory vehicles only, and dealers had to disclose the repair to buyers.[9]

Reported symptoms

  • Check-engine light
  • Transmission stuck in a default gear

Missing start/stop accumulator bolts (recall 20V-668) (2018–2020)

GM's recall report says supplier-built start/stop accumulators were found with missing bolts, and bench testing showed potential early failure for one of the two affected transmission designs, which the report does not name. GM's recall bulletin lists the affected transmissions as its front-wheel-drive 6- or 9-speed units. A resulting oil leak can progress to a loss of propulsion.[11][12][13]

Reported symptoms

  • Transmission fluid spots under the front of the vehicle
  • Loss of drive

GM 6T40 / 6T45 recalls

Transmission-related NHTSA safety recalls (campaign numbers link to NHTSA)
NHTSA campaignReportedVehiclesSummary
20V6682020-10-29194,105 GM vehicles including 2018–2020 Equinox and Terrain, 2018–2019 Cruze and LaCrosse, 2018 Malibu and 2019 Encore194,105 vehiclesThe start/stop accumulator endcap may be missing bolts, which can cause a transmission oil leak and loss of propulsion, and a fire risk near an ignition source. GM's bulletin describes the affected transmissions as its front-wheel-drive 6- or 9-speed, so not every vehicle in the recall has a 6T40/6T45; most of the population was Cruze and Malibu. Dealers inspect the accumulator and replace it if bolts are missing.[13]

Recall repairs are free at franchised dealers regardless of age or owner. Check a specific car by its 17-digit VIN at nhtsa.gov/recalls or with the CarWhere recall check.

NHTSA owner complaints: the power-train signal

Owners file complaints with NHTSA and tag each with the components involved. The tables below count, for each model year, how many complaints include NHTSA’s “power train” component (transmission, transfer case and driveline). Raw counts are not adjusted for sales volume or vehicle age, so compare the power-train share across years of the same model rather than across models.

Buick Encore

In the model years that used the GM 6T40 / 6T45 (highlighted), 66 of 549 NHTSA owner complaints (12%) list the power train as a component, versus 25% across the other Buick Encore model years in the same snapshot. The highest count is the 2015 model year, with 11 power-train complaints.

Buick Encore: NHTSA owner complaints by model year, all components vs. power train
Model yearAll complaintsPower-train complaintsPower-train share
2013GM 6T40 / 6T4552713.5%
2014GM 6T40 / 6T4560915%
2015GM 6T40 / 6T45123118.9%
2016GM 6T40 / 6T45771114.3%
2017GM 6T40 / 6T4587910.3%
2018GM 6T40 / 6T45711014.1%
2019GM 6T40 / 6T4579911.4%
202019421.1%
20219333.3%
20228225%

Buick Verano

In the model years that used the GM 6T40 / 6T45 (highlighted), 52 of 439 NHTSA owner complaints (11.8%) list the power train as a component. The highest count is the 2014 model year, with 19 power-train complaints.

Buick Verano: NHTSA owner complaints by model year, all components vs. power train
Model yearAll complaintsPower-train complaintsPower-train share
2012GM 6T40 / 6T4510676.6%
2013GM 6T40 / 6T451061312.3%
2014GM 6T40 / 6T451011918.8%
2015GM 6T40 / 6T455846.9%
2016GM 6T40 / 6T4559711.9%
2017GM 6T40 / 6T459222.2%

Chevrolet Equinox (includes V6 models)

In the model years that used the GM 6T40 / 6T45 (highlighted), 531 of 3,536 NHTSA owner complaints (15%) list the power train as a component, versus 10.4% across the other Chevrolet Equinox (includes V6 models) model years in the same snapshot. The highest count is the 2010 model year, with 182 power-train complaints.

Chevrolet Equinox (includes V6 models): NHTSA owner complaints by model year, all components vs. power train
Model yearAll complaintsPower-train complaintsPower-train share
2008370164.3%
2009941010.6%
2010GM 6T40 / 6T4578418223.2%
2011GM 6T40 / 6T4578014518.6%
2012GM 6T40 / 6T456828412.3%
2013GM 6T40 / 6T457478010.7%
2014GM 6T40 / 6T45543407.4%
2015678639.3%
2016391266.6%
20172703211.9%
20183886316.2%
20192903411.7%
20202913813.1%
2021871618.4%
2022153106.5%
20238533.5%
2024651015.4%
20252062914.1%

Source: NHTSA owner-complaint records (api.nhtsa.gov complaintsByVehicle), snapshot as of 2026-07-14. Complaints are unverified owner reports; one complaint can list several components.

Buying a used car with the GM 6T40 / 6T45: what to check

  1. Run the VIN through NHTSA's recall lookup; on 2018–2020 models confirm recall 20V-668 shows as complete if it applies.
  2. Check the RPO code on the glovebox label (for example MH8, MHH or MNH) to confirm which transmission is fitted.
  3. Look under the car between the engine and transmission for fresh fluid, the leak point described in GM bulletin PI0950A.
  4. On the test drive, confirm the car engages Drive and Reverse promptly from a cold start and shifts without slipping.
  5. Ask for records of any transmission, torque-converter seal or fluid-pump repair.

Related research

Year-by-year verdicts for models with the GM 6T40 / 6T45

Engines and model known-issues pages

Compare other transmissions

All transmissions: reliability and years to avoid

Frequently asked questions

Which cars have the GM 6T40 or 6T45?

GM bulletins list the 6T family in 2010–2014 Chevrolet Cruze, Sonic, Malibu, Equinox, Trax, Captiva Sport and Orlando, Buick Verano, Encore, Regal and LaCrosse, and GMC Terrain models, and a 6T40 in the 2018–2019 Equinox and Malibu 1.5L and Encore 1.4L. Check the RPO code to confirm.

Why won't my 6T40 car move or start?

GM bulletin PI0324F says no-drive, no-crank and no-start conditions on 2011–2014 6T-family vehicles may be caused by low or no line pressure from a damaged transmission fluid pump. GM tells technicians to perform a line-pressure check before replacing the valve body or control-solenoid assembly.

Is there a recall on the GM 6T40?

GM handled the documented 2010–2014 problems (fluid-pump damage and converter-seal leaks) through service bulletins, not safety recalls. Recall 20V-668 covers missing start/stop accumulator bolts on some 2018–2020 GM vehicles with front-wheel-drive 6- or 9-speed automatics, including some Equinox, Terrain, Cruze, Malibu and Encore models. Check any VIN for open recalls.

Is a bump after the 2–3 shift normal?

For 2013 Encore, Regal, Verano, Cruze, Malibu, Sonic and Trax models with the 6T40 (MH8), GM bulletin PI1287 says a bump shortly after the 2–3 shift on a restart after a short stop is part of the transmission calibration, a normal characteristic, and should not be repaired.

Why won't my 2018–2019 Equinox 1.5L shift into the top gears in cold weather?

GM bulletin 18-NA-035 says that in freezing or near-freezing humid weather the engine controls may request a lower gear to prevent icing in the charge-air cooler. GM calls this normal operation and tells dealers not to replace parts for it.

How CarWhere compiled this page

Every problem, recall, warranty extension and settlement above is CarWhere’s own summary of a primary record — NHTSA recall campaigns, manufacturer service bulletins and warranty-extension notices filed with NHTSA, manufacturer press material, and court or settlement-administrator records — and is numbered to its source below. We list a model year under “years to avoid” only when a manufacturer, regulator or court record ties it to the transmission. Complaint counts come from NHTSA’s public owner-complaint data, counted once per complaint. We do not estimate failure rates or repair costs. See also the years-to-avoid methodology.

Sources

Descriptions are CarWhere’s own summaries of the records below. Recall details are as reported to NHTSA by the manufacturer.

  1. GM PI0324F (Dec. 2013): No forward, no reverse, no crank, engine cranks but will not start — perform transmission line pressure check (6T30/6T40/6T45/6T50) — General Motors (via NHTSA)
  2. GM PI0950A (Feb. 2015): Automatic transmission fluid leak from torque converter housing area — General Motors (via NHTSA)
  3. GM Bulletin 18-NA-035 (Feb. 2019): Transmission no command overdrive ranges during cold ambient temperatures — General Motors (via NHTSA)
  4. 2012 Chevrolet Equinox FWD — transmission options — fueleconomy.gov (U.S. DOE/EPA)
  5. GM PI0604C (May 2013): Information on 6T30/6T40/6T45/6T50 automatic transmission product updates (Gen 2) — General Motors (via NHTSA)
  6. GM PI1403 (Feb. 2015): 2015 Chevrolet Trax new model features (6T40 RPO MH8/MHB) — General Motors (via NHTSA)
  7. 2015 Buick Encore — transmission options — fueleconomy.gov (U.S. DOE/EPA)
  8. 2014 Buick Verano — transmission options — fueleconomy.gov (U.S. DOE/EPA)
  9. GM Service Update 13282A (Sept. 2013): Transmission snap ring misalignment — inventory vehicles only — General Motors (via NHTSA)
  10. GM PI0324E (Dec. 2012): No forward, no reverse, no crank — perform transmission line pressure check — General Motors (via NHTSA)
  11. Part 573 Safety Recall Report 20V-668 (GM, Oct. 29, 2020) — NHTSA
  12. GM Product Safety Recall bulletin N202313440 (20V-668), Oct. 2020 — General Motors (via NHTSA)
  13. NHTSA recall 20V-668: Missing bolts on start/stop accumulator endcap — NHTSA
  14. GM PI1287 (July 2014): Bump feeling after shifting into 3rd gear (6T40, RPO MH8) — General Motors (via NHTSA)

Independent reference compiled by CarWhere Research — not affiliated with or endorsed by any manufacturer or transmission supplier. Product and model names are trademarks of their owners.