2017-2020 Buick Envision 2.5L AWD Transmission: Problems, Identification, and Used Replacement

Identifying the Correct 2.5L AWD Transmission

The 2017-2020 Buick Envision with the 2.5L engine and All-Wheel Drive (AWD) uses a specific Hydra-Matic 6-speed automatic transaxle, known as the GM 6T50. To ensure you are buying the correct replacement, you must verify several key identifiers on your vehicle, as parts from other models will not fit.

Transmission ID Tag Location

The most precise identifier is the barcode label on the transmission case itself. This tag is typically on the right side of the housing, near the top. For this specific unit, the model code on the tag should read 7HCW and the original GM part number is 24280907 (or its replacements, 19434037 and 24290329).

Common Failure Symptoms

When the 6T50 transmission begins to fail, it can exhibit several distinct symptoms. If you experience any of the following, it may be time for a replacement.

• Loss of Gears: A sudden and complete loss of 3rd, 5th, and Reverse gears is a classic sign of internal failure, often related to a broken 3-5-Reverse wave plate.
• Erratic or Harsh Shifting: The transmission may slam into gear, hesitate, or shift at the wrong times. This often points to problems with the internal solenoids or the control module (TEHCM).
🎬 Watch: What you need to know about TEHCM replacements
• Shudder or Vibration: A shaking or shuddering feeling, sometimes described as driving over rumble strips, during light acceleration at steady speeds is a common complaint. This is often caused by a failing torque converter clutch or contaminated fluid.
• No Movement: The engine may run, but the vehicle won't move in any gear range. This can be caused by a failed fluid pump or catastrophic internal damage.
• Overheating: A trouble code such as P0218 indicates the transmission fluid is over temperature, which can quickly lead to internal damage. This is often caused by incorrect fluid levels.

Diagnostic Flowchart

Known Problems, Bulletins, and Recalls

The 6T50 transmission family has several well-documented issues. While no transmission-specific safety recalls have been issued for the 2017-2020 Envision, owners should be aware of the following technical service bulletins (TSBs) and common problems.

3-5-Reverse Wave Plate Failure

A weak point in early-to-mid generation 6-speed automatics is the wave plate inside the 3-5-Reverse clutch drum. This thin, spring-like plate can fracture or its snap ring can pop out, sending metal debris throughout the transmission and causing an immediate loss of the corresponding gears. This is a severe failure that requires a complete rebuild or replacement.

Torque Converter Clutch (TCC) Shudder

Many owners report a shudder or vibration at low to medium speeds. This is often traced to the transmission fluid becoming contaminated with moisture or degrading, which affects the performance of the torque converter clutch. GM has issued bulletins for similar transmissions, like 16-NA-175 and PIP6087, with the primary remedy being to perform a complete fluid exchange with fresh DEXRON-VI fluid and, in some cases, update the Transmission Control Module (TCM) software.

TEHCM and Solenoid Failure

The Transmission Electro-Hydraulic Control Module (TEHCM) is the transmission's computer, and it is located inside the oil pan. This unit, along with its integrated solenoids, can fail from wear or contamination from internal debris. This leads to a wide range of shifting problems and requires replacing the entire TEHCM assembly, which must then be programmed to the vehicle.

Damaged Transmission Fluid Pump

According to GM Preliminary Information bulletin PI0324F, some units may experience a failure of the fluid pump, even at low mileage. This causes a loss of hydraulic pressure, resulting in harsh shifts, no-start conditions, or a complete inability to move. This requires transmission removal to replace the pump.

Final Drive Gear Set Bolt Failure

Specifically on AWD configurations, the bolts securing the final drive components can shear under heavy load. This leads to catastrophic failure of the final drive gear set and bearings, requiring a full replacement of the transaxle.

Replacement Cost Estimates

The cost to replace a 2017-2020 Envision 2.5L AWD transmission varies based on the type of replacement unit you choose. The estimates below do not include taxes or shop supply fees.

Installation and Programming: Critical Steps

Proper installation is essential for the longevity of a replacement transmission. This is an expert-level job requiring special tools like an engine support fixture, a subframe/cradle jack, and a heavy-duty transmission jack. Several common mistakes can cause immediate failure of the new unit.

Required Programming (TEHCM)

The internal control module (TEHCM) is the brain of the transmission. A used transmission includes its original TEHCM, but it will not work in your vehicle until it is electronically programmed.

Key Installation Gotchas

• Temperature-Sensitive Fluid Level Check: This transmission has no dipstick. The fluid level must be checked via a plug on the side of the case while the engine is idling and the fluid is strictly between 86°F and 122°F (30°C to 50°C). Checking it when cold or with the engine off will cause several quarts to pour out, resulting in a severely underfilled transmission.
• Dowel Pins: Ensure alignment dowel pins between the engine block and transmission bellhousing are present and in good condition to prevent flexplate and pump damage.
• Electrical Connectors: Ensure that the electrical connectors for the auxiliary electric fluid pressure system (Start-Stop functionality) are completely clean, dry, and securely plugged in during installation.

What Fails at Every Mileage Band

Under 60,000 Miles

Transmissions in this range are generally healthy, but early failures can still occur, primarily due to fluid degradation or electronic faults.

• Known Failures: Torque Converter Clutch (TCC) shudder due to fluid properties, TEHCM/solenoid malfunctions causing harsh shifts, premature 3-5-Reverse wave plate failure, and fluid leaks from axle seals or the pan gasket.
• ✓Do during install (required): Perform a full transmission fluid exchange with new DEXRON-VI fluid (approx. 9 to 10 quarts). Ensure the mandatory TEHCM VIN-programming and Service Fast Learn are performed. Thoroughly flush the transmission cooler and lines.
• ✓Do during install (recommended): Replace external seals such as axle output seals and the torque converter/front pump fluid seal.
• ✓Cheap insurance while the engine is out: Inspect the included torque converter and replace it if the donor fluid shows any signs of contamination.

60,000 - 100,000 Miles

This is the critical wear window where known weak points begin to fail, especially if the original fluid was never changed.

• Known Failures: The risk of 3-5-Reverse wave plate fracture increases significantly. Solenoids inside the TEHCM wear out or clog. The torque converter lock-up clutch can wear out completely, contaminating the fluid. Valve body wear causes pressure losses and slipping.
• ✓Do during install (required): All required items from the Under 60k band.
• ✓Do during install (recommended): Replace the transmission filter and pan gasket (note: the internal pump filter is non-serviceable without splitting the case, but external pan seals should be replaced). Inspect and replace transmission mounts if they show signs of wear or cracking.
• ✓Cheap insurance while the engine is out: Strongly consider replacing the included used torque converter with a new or remanufactured unit as a preventative measure, as it is a primary failure point in this mileage range.

100,000 - 150,000+ Miles

Units in this range are approaching the end of their expected service life. Wear is extensive across all internal components.

• Known Failures: Catastrophic internal failures (wave plate, clutch packs, pump) are highly likely. Complete TEHCM failure due to heat and contaminated fluid is common. General wear leads to slipping in multiple gears. Final drive and bearing failures occur on AWD models.
• ✓Do during install (required): All required items from previous bands. Given the high mileage, installing a new torque converter is non-negotiable for reliability.
• ✓Do during install (recommended): The buyer should have a strong expectation that other wear items (clutches, seals) may have limited life remaining. A lower-mileage unit is strongly recommended over a high-mileage one.
• ✓Cheap insurance while the engine is out: Have a transmission shop inspect the valve body and solenoids before installation.

Real Owner Experiences

Repair or Replace?

Deciding whether to repair your existing transmission or replace it entirely depends on the specific failure mode.

When Replacement is Smarter: Replacing the unit with a used ($750 - $1,500) or remanufactured ($2,500 - $4,500) assembly is the better option when there is catastrophic internal damage, such as a final drive gear set failure, which makes a rebuild prohibitively expensive due to the cost of hard parts. It is also smarter if multiple internal components have failed, or if you prioritize a longer-term, nationwide warranty often provided by remanufacturers.

Freight and Delivery Reality

If you are ordering a used replacement transmission online, be prepared for how it will arrive. This assembly weighs approximately 192 lbs and measures roughly 35" x 30" x 25" before crating. Because of its size and weight, it ships as LTL (Less Than Truckload) freight on a wooden pallet—it will NOT arrive via standard parcel services like UPS Ground or FedEx Home Delivery.

You must specify a commercial delivery address with a loading dock or forklift, or request a liftgate service for residential delivery. Always perform a pre-purchase verification interview with the seller to confirm the exact VIN and mileage of the donor vehicle. When the freight carrier arrives, inspect the transmission carefully for any shipping damage (such as cracked bellhousings or broken sensors) before signing the delivery receipt.

Frequently Asked Questions