2020 Cadillac CT5 2.0L AWD 10-Speed Transmission: Problems, Identification, and Used Replacement
Identify the MHS 10-speed transmission, understand common valve body failures, and learn what to look for when buying a used OEM replacement assembly.
- Verify fitment using RPO codes MHS (transmission) and F46 (AWD); this transmission is specific to the 2020 CT5 2.0L AWD and does not interchange with other years or engines.
- The most common failure is excessive valve body wear, which may be covered for free by a dealer under GM's Special Coverage Program N242454441 (15 years/150,000 miles).
- Replacement is not a DIY task and requires mandatory Solenoid Characterization (MCVM) and VIN-specific programming using proprietary GM software after installation.
- Before installing a replacement unit, it is critical to professionally flush the transmission cooler and lines and use only new ACDelco DEXRON ULV fluid to prevent immediate failure.
- If experiencing harsh shifts or overheating, first inspect the transmission cooler lines for twists or damage as per TSB 22-NA-182, as this is a simple and inexpensive repair.
Part Identification: Confirming the MHS 10-Speed Transmission
The 2020 Cadillac CT5 with the 2.0L turbocharged engine and All-Wheel Drive (AWD) uses a specific version of the GM Hydra-Matic 10-speed automatic transmission. This unit is identified by the Regular Production Option (RPO) code MHS. RPO codes are three-character codes that GM uses to identify all the factory-installed options on a vehicle. While it belongs to the 10L60/10L80 family, the MHS code signifies the exact version calibrated for this vehicle and drivetrain combination.
Before purchasing a replacement transmission, you must confirm your vehicle requires this exact unit. An incorrect transmission may not fit or function due to differences in electronic controls, calibrations, and physical mounting.
How to Verify Fitment on Your Vehicle:
| Check Point | Requirement | Details |
|---|---|---|
| VIN | 8th Digit must be '4' | This identifies the 2.0L LSY Turbo engine. |
| RPO Code Label | Must have MHS & F46 | Scan the QR code on the driver's door jamb. MHS confirms the 10-speed transmission, and F46 confirms the All-Wheel Drive system. |
| Exclusions | Must NOT have V03 | Verify your vehicle does not have the extra cooling capacity package (RPO V03). |
Warning: This MHS transmission is specific to the 2020 CT5 2.0L AWD model. It will NOT interchange with Rear-Wheel Drive (RWD) models, models with the 3.0L V6 or 6.2L V8 engines, or CT5 models from 2021 and later, which used a different transmission variant.
Common Failure Symptoms
A failing transmission can present several distinct symptoms. While these strongly suggest an internal transmission problem, a professional technician should always perform a full diagnosis to rule out external sensors, wiring, or a faulty Transmission Control Module (TCM).
- Harsh or Abrupt Shifting: The vehicle may jerk or bang into gear, particularly during downshifts.
- Transmission Shudder or Surge: A vibration or surging feeling during acceleration or while cruising at a steady speed.
- Wheel Lock-Up: In rare but severe cases, a critical internal failure can cause the wheels to momentarily lock up, creating a significant safety risk.
- Loss of Reverse Gear: A known internal mechanical failure can result in a complete loss of the ability to reverse.
- Overheating: The transmission may run at excessively high temperatures, which can be caused by internal issues or restricted fluid flow from the cooler.
- Check Engine Light: Faults within the transmission will often trigger a Check Engine Light and store Diagnostic Trouble Codes (DTCs) like P0747, P0700, or P27EC.
Diagnostic Flowchart
Known Issues, Recalls, and Technical Service Bulletins (TSBs)
Several documented issues affect this 10-speed transmission family. Always check your vehicle's VIN on the NHTSA website to see which recalls or service campaigns apply.
| Identifier | Title / Subject | Summary and Remedy |
|---|---|---|
| NHTSA Recall 25V-148 (GM N242480630) | Excessive Valve Body Wear & Wheel Lock-Up | Addresses a defect where the control valve wears, potentially causing a momentary wheel lock-up. The remedy is a dealer-installed TCM software update that monitors valve performance and activates a limp mode if wear is detected. |
| Special Coverage N242454441 | Valve Body Wear & DTC P0747 | Extends the valve body warranty to 15 years or 150,000 miles. If the vehicle has severe rough shifting and DTC P0747, dealers will replace the valve body assembly at no charge. |
| TSB 22-NA-182 | Harsh Shifts, Shudder, and Overheating | Informs technicians that a twisted or misshaped transmission cooler line can cause these symptoms and trigger DTC P27EC. The fix is to inspect and replace the affected line. |
| TSB PIP6008D | DTC P2714 & Loss of Reverse | Addresses an internal failure where a dislodged retaining ring leads to a loss of reverse. Requires transmission disassembly to repair the mechanical failure. |
| Customer Program 17335 | Potential for Factory Overfill | Some models may have been overfilled with fluid from the factory, causing aeration, high temperatures, and erratic shifts. The remedy is to verify and adjust the fluid level. |
What Fails at Every Mileage Band
Pro Tip: The mileage bands below describe what typically fails on these transmissions at various stages of life. If you are buying a used replacement unit, use the checklists provided to perform critical maintenance before and during the installation of your purchased transmission.
Under 60,000 Miles
The most significant issue in early life is premature wear of the transmission control valve body. This causes harsh shifting, shudders, and prompted NHTSA Recall 25V-148. Fluid leaks from factory gaskets or seals can also occur. Some owners report total failures well before 60,000 miles.
- ✓Do during install (required): Perform a professional transmission cooler line flush to remove any debris from the old unit.
- ✓Do during install (required): Replace the transmission fluid filter (ACDelco TF937 / GM Part #24294355) and pan gasket with new parts.
- ✓Do during install (required): Use only new, correct specification ACDelco DEXRON ULV (Ultra-Low Viscosity) Full Synthetic Fluid.
- ✓Do during install (recommended): Given the known issues, if installing a used unit even at low mileage, consider having a transmission shop inspect the valve body for wear before installation.
- ✓Cheap insurance while the engine is out: Replace the front pump/torque converter seal and axle seals while the transmission is out.
60,000 - 100,000 Miles
Valve body wear continues to be the primary failure point. Torque converter clutch materials can wear out, causing lockup issues and shuddering under load. Contaminants from normal wear (aluminum oxide dust) can saturate the fluid and filter, accelerating wear on the bare aluminum valve body bores.
- ✓Do during install (required): Ensure the replacement unit has had the valve body recall (software or hardware update) addressed. If not, this must be done at a dealer after installation.
- ✓Do during install (recommended): Consider replacing the torque converter with a new or quality remanufactured unit as a preventative measure, since the original is a known weak point.
- ✓Cheap insurance while the engine is out: Replace the front pump and axle seals.
100,000 - 150,000 Miles
The general service life for this transmission family is estimated to be between 100,000 and 150,000 miles under average use. Long-term wear from contaminated fluid can lead to significant valve body and internal component damage. Clutch pack failure due to material breakdown or hydraulic pressure loss is more likely.
- ✓Do during install (required): At this mileage, installing a used transmission without replacing the torque converter is highly inadvisable. A new OEM or upgraded aftermarket torque converter should be installed.
- ✓Do during install (recommended): A transmission shop should inspect and potentially replace key wear items like the valve body, solenoids, and clutch packs before installing a unit with this mileage.
- ✓Cheap insurance while the engine is out: Replace all accessible external seals and gaskets.
Real Owner Experiences
The following table highlights real-world experiences from owners dealing with this transmission family.
| Source | Mileage | What Happened | Cost |
|---|---|---|---|
| gm-trucks.com Forum | just under 70k miles | Owner of a 2020 truck with a 10-speed reported shuddering at low RPMs, harsher shifts, and some surging. The dealer diagnosed it as needing a new torque converter and valve body. | Not specified, likely warranty. |
| Reddit r/Silverado | 22k miles | A user reported their 10-speed transmission 'crapped out' at only 22,000 miles. | Not specified, likely warranty. |
| NHTSA Complaint | approximately 65,000 | A 2020 Cadillac CT5 owner experienced transmission issues leading to a recall-related complaint. | Not specified. |
| Reddit r/Cadillac | 22,000 miles | A 2023 CT4-V owner had the valve body replaced under warranty. | Warranty |
| Reddit r/Cadillac | 67,000 miles | A user bought a 2020 CT5 at 67k miles. After the recall service was performed, it still jerked at certain speeds. A full fluid and filter flush resolved the issue. | Not specified. |
| Reddit r/Cadillac | 81,000 miles | A 2020 CT5 Sport AWD had the recall software service performed at 81k miles. The same issue of the car locking up and not going past 20mph returned after multiple repair attempts by a third-party mechanic. | Handled by service contract. |
| GM-Trucks.com Forum | 67,000 miles | Owner performed a fluid and filter change. The old fluid was dark but did not smell burnt. The DIY job was noted as not being overly difficult. | DIY parts cost (9.5 quarts of ULV fluid, filter, exhaust seals). |
| Reddit r/Silverado | 92,000 miles (146,000 km) | A user with a 10-speed transmission paired with a 3.0L engine reported no major issues at this mileage. | N/A |
| Jalopnik Article | well north of 100,000 miles, and even 150,000 miles | The article notes that while many owners have problems, some are driving with high mileage and no issues, indicating highly variable reliability. | N/A |
| 2000 | Dealer diagnosed a transmission problem causing uneven idle and stalling. Required a valve body replacement, which was backordered for months. The repair was covered under the factory warranty. | 0 | |
| N/A | Owner of a truck with a related 10-speed transmission was quoted $1400 for the valve body part and $2200 for labor by a dealer. | N/A | |
| 89000 | Owner of a truck with a 10L80 transmission was quoted $7,021.50 by a dealer for a new replacement transmission (Part #19540602). This price included a $5,000 core charge. | N/A |
Repair or Replace?
When facing transmission issues, deciding whether to repair your current unit or replace it entirely depends on the specific failure and your budget.
When Repair Makes Sense
- Excessive Valve Body Wear: This is the most common point of failure. If the vehicle is within the 15-year/150,000-mile Special Coverage Program (N242454441), the valve body replacement should be free at a dealership. If out of warranty, a dealer repair could cost up to $3,600, while using a remanufactured valve body ($320-$550 part cost) at an independent shop is significantly cheaper. This repair makes sense when the rest of the transmission's hard parts are in good condition.
- Twisted/Misshaped Transmission Cooler Line: If symptoms include harsh shifts, shuddering, and overheating, this should be the first inspection point (TSB 22-NA-182). Correcting a twisted cooler line is a simple, inexpensive repair ($200-$500) that can prevent catastrophic failure.
- Failed Pressure Control Solenoid: If diagnostics pinpoint a specific solenoid as 'stuck on' (DTC P0747), replacing the individual solenoid is highly cost-effective. A solenoid part costs around $150-$250, with labor around $80-$120.
When Replacement is Smarter
Replacement with a complete used or remanufactured unit is the smarter choice when there is evidence of widespread internal failure beyond the valve body. This includes symptoms like loss of multiple gears, significant metal debris in the transmission pan, or a cracked case. Given the high cost of labor to remove and reinstall the transmission (estimated at 7 to 12 hours, or $1,000 to $2,400), it is often more economical to replace the entire unit rather than paying for labor twice if an initial component-level repair fails to solve the problem.
Questions to Ask Your Installer:
- Have you confirmed this is not a valve body issue covered under GM's Special Coverage Program N242454441?
- Did you inspect the transmission cooler lines for twists or damage as per TSB 22-NA-182?
- Will you be performing a complete hot flush of the transmission cooler and lines before installing the replacement?
- Do you have the GM SPS2 software and a J-2534 device to perform the mandatory Solenoid Characterization (MCVM) and VIN-specific programming?
- How will you document the Transmission Unique Number (TUN) and Part Unique Number (PUN) from the replacement unit before it is installed?
- What is your process for ensuring the torque converter is fully seated before mating the transmission to the engine?
- What is the all-in quote, including the correct DEXRON ULV fluid, filter, seals, and programming?
Replacement Cost Estimates
The cost to replace a transmission varies based on the type of replacement unit, labor rates, and location. The following are general market estimates.
| Part or Service | Estimated Cost (USD) | Notes |
|---|---|---|
| New OEM | $4,300 - $7,100 | A brand new unit from a Cadillac dealer. Prices can be high and may have a significant core charge. |
| Remanufactured OEM | $3,200 - $5,300 | Rebuilt by a third party to meet or exceed original specifications, often with updates to fix known flaws. |
| Used OEM | $1,700 - $2,700 | A direct pull from a wrecked donor vehicle. Mileage and condition can vary widely. |
| Shop Labor | $1,000 - $2,400 | Includes removal, installation, and programming. Estimated at 7 to 12 hours of shop time. |
Freight & Delivery Reality
If you are purchasing a used or remanufactured transmission online, it will not arrive in a standard cardboard box via regular mail. This assembly weighs approximately 295 lbs and measures roughly 40" x 28" x 30" before crating. It ships as Less-Than-Truckload (LTL) freight strapped to a wooden pallet.
Because of its size and weight, delivery requires a commercial loading dock or a truck equipped with a liftgate. Always inspect the transmission carefully before signing the delivery receipt. Look for any damage to the bellhousing, oil pan, or electrical connectors that may have occurred during transit. A pre-purchase verification interview with the seller is an industry best practice to ensure you are getting the exact MHS unit you need.
Installation and Programming: What to Know
Installing this transmission is a complex job recommended for professional technicians with the correct tools and software. It is not considered a DIY-friendly task due to the electronic programming required. The job requires special tools, including a transmission jack, engine support fixture, torque converter holding tool, high-quality fluid pump, and an advanced scan tool capable of reading real-time transmission fluid temperature.
Required Programming
This transmission cannot simply be swapped. It requires two critical electronic procedures:
- Solenoid Characterization (MCVM): The solenoids that control shifting are individually tested at the factory, and their unique flow data is recorded. This data, linked to the Transmission Unique Number (TUN) and Part Unique Number (PUN) on the transmission case and valve body, must be programmed into the vehicle's external Transmission Control Module (TCM).
- VIN-Specific Programming: The vehicle's main computer must be programmed to accept the new transmission to ensure all systems communicate correctly.
This programming requires a J-2534 pass-thru device or a GM MDI 2 scan tool with an active subscription to GM's Service Programming System (SPS2).
Warning: Before installing the transmission, you MUST write down or photograph the 16-digit TUN from the barcode label on the case and the PUN from the valve body. These labels will be impossible to see once the transmission is bolted into the vehicle.
Key Installation Steps & "Gotchas"
- Torque Converter Seating: The torque converter must be fully seated into the transmission's front pump before mating the transmission to the engine. This usually involves feeling three distinct "clicks" or drops as it engages. Failure to do this will crack the pump when the bellhousing bolts are tightened.
- Fluid Cooler Flush: The transmission fluid cooler and lines must be professionally flushed to remove any metal debris from the previous failed unit. Skipping this step will contaminate the replacement transmission and cause it to fail quickly.
- Correct Fluid: This transmission requires ACDelco DEXRON ULV (Ultra-Low Viscosity) fluid. Using any other type, including Dexron VI or a generic multi-vehicle ATF, will cause damage.
- Shift-by-Wire Alignment: This is a shift-by-wire transmission; ensure the internal park pawl actuator lever is properly aligned and the electrical connector is fully seated.
- Relearn Procedure: Perform the adaptive shift learning reset and drive cycle relearn procedure after programming is complete.
Pro Tip: The fluid level check procedure is very specific. The engine must be running, the vehicle must be perfectly level, and the transmission fluid temperature must be strictly within the specified range (sources differ: 95-113°F vs 160-180°F). The level is checked via a plug on the side of the transmission case.
Arrival Inspection for Your Used Transmission
When your used replacement transmission arrives, you must inspect it before installation. This prevents you from installing a damaged unit.
Pan and Magnet Inspection
Remove the bottom transmission fluid pan. Look at the small magnet attached to the inside of the pan. A light coating of fine, dark fuzz is normal wear. However, large metal shavings, chunks, or brass-colored flakes mean the internal gears or bearings are broken.
Fluid Color and Smell
Check the small amount of fluid left inside the transmission pan. Normal transmission fluid is red or light brown. If the fluid is thick, dark black, or has a strong burnt smell, the internal clutches (friction plates that change gears) are burned out.
Converter Hub and Input Spline Condition
If the transmission includes a torque converter (the fluid coupling that connects the engine to the transmission), inspect its hub. The hub is the smooth metal tube sticking out of the back. It must be perfectly smooth. Deep grooves on this hub will tear the front seal and cause massive fluid leaks.
Next, check the input splines. These are the grooved teeth on the main shaft that slide into the torque converter. The teeth must be straight and sharp. If the splines are worn down, twisted, or chipped, the transmission will slip or fail to move the vehicle.
Frequently Asked Questions (FAQ)
Is the Transmission Control Module (TCM) included with a used transmission?
No. For this vehicle, the T93 TCM is an external computer mounted under the hood on the passenger-side fender. It is not part of the transmission assembly and is not included with a used unit.
Can I reuse my old torque converter?
No. A used or remanufactured transmission assembly includes a matching torque converter. You should never reuse your old one, as it is likely contaminated with debris from the failed transmission.
What happens if I skip the programming?
If the solenoid characterization and VIN programming are not performed, the transmission will exhibit harsh shifting, incorrect gear engagement, and may enter a limp mode, making the vehicle undrivable.
What fluid does the 2020 CT5 2.0L AWD transmission take?
It requires ACDelco DEXRON ULV (Ultra-Low Viscosity) Full Synthetic Fluid. GM's severe service schedule recommends a fluid and filter change every 45,000 miles to prevent premature valve body wear.
Does this transmission fit the 2021 CT5?
No. General Motors transitioned the CT5 2.0L to the lighter-duty 10L60 transmission for the 2021 model year. This specific MHS unit only fits the 2020 model year.
Helpful Videos
Technical Specifications
RPO Code: MHS; Transmission Family: GM Hydra-Matic 10L60/10L80; Speeds: 10-Speed Automatic; Application: 2020 Cadillac CT5; Engine: 2.0L LSY Turbo (VIN 8th Digit '4'); Drivetrain: All-Wheel Drive (RPO F46); Required Fluid: ACDelco DEXRON ULV (Ultra-Low Viscosity); TCM Type: External T93; Approximate Weight: 295 lbs; Shipping Dimensions: 40" x 28" x 30"
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- Cadillac CT5:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Part Identification: Confirming the MHS 10-Speed Transmission
- How to Verify Fitment on Your Vehicle:
- Common Failure Symptoms
- Diagnostic Flowchart
- Known Issues, Recalls, and Technical Service Bulletins (TSBs)
- What Fails at Every Mileage Band
- Under 60,000 Miles
- 60,000 - 100,000 Miles
- 100,000 - 150,000 Miles
- Real Owner Experiences
- Repair or Replace?
- When Repair Makes Sense
- When Replacement is Smarter
- Questions to Ask Your Installer:
- Replacement Cost Estimates
- Freight & Delivery Reality
- Installation and Programming: What to Know
- Required Programming
- Key Installation Steps & "Gotchas"
- Arrival Inspection for Your Used Transmission
- Pan and Magnet Inspection
- Fluid Color and Smell
- Converter Hub and Input Spline Condition
- Frequently Asked Questions (FAQ)
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