8-Speed Automatic Transmission Assembly for 2020-2023 Cadillac CT4
Product Notes Read before buying
This is an 8-speed automatic transmission for All-Wheel Drive (AWD) models with the 2.0L engine only. Please verify your vehicle has the transmission option code M5N to ensure compatibility.
Voice or type your vehicle details and Wrenchy will confirm fitment in seconds.
Vehicle Fitment Guide
This part fits the following vehicles:
| SubmodelSUB- MODEL |
Body Style | Years | Engine | Attributes |
|---|---|---|---|---|
| Luxury | Sedan | 2020 - 2023 | L4 2.0L Turbo | AWD | Automatic |
| Premium Luxury | Sedan | 2020 - 2023 | L4 2.0L Turbo | AWD | Automatic |
| Sport | Sedan | 2020 - 2023 | L4 2.0L Turbo | AWD | Automatic |
| 2021 - 2022 |
Know This Transmission Before You Buy
The research behind our purchase interview — recalls, bulletins and real install economics for this transmission family:
A quick look at your own vehicle makes sure the right transmission shows up:
- Verify the 8th digit of the VIN to confirm the 2.0L Turbo (LSY) engine.
- Verify the vehicle is All-Wheel Drive (AWD).
- Confirm RPO code M5N on the Service Parts Identification label (QR code on driver's door jamb or sticker in glovebox).
What the install really takes — plan and budget with confidence:
Special tools this job needs:
- Transmission jack
- Engine support fixture
- GM-compatible scan tool (GDS2 / Techline Connect) capable of SPS2 programming
- Fluid fill adapter (GM tool DT-51190 or equivalent)
- Fluid transfer pump
Budget for these consumables at install:
- Mobil 1 Synthetic LV ATF HP ('Blue Label' formula, GM Part No. 19417577)
- Transmission filter (GM Part No. 24274616 or TF922)
- Pan gasket (GM Part No. 24260071)
- Front pump / torque converter input seal
- Transfer case input shaft seal
What your vehicle’s computers will need after the swap:
What’s involved: Solenoid Characterization Programming (TUN/PUN matching) and Transmission Service Fast Learn (SFL)
The GM 8L45 uses Variable Force Solenoids requiring precise flow rate calibration. You must use GM SPS2 to enter the replacement transmission's Transmission Unique Number (TUN) into the vehicle's TCM. A 'Service Fast Learn' adaptive reset must then be executed. Skipping this causes harsh shifts, slipping, or limp mode.
Pro tips for a smooth first start-up — hand them to whoever does the install:
- Torque Converter Seating: Ensure the torque converter is fully seated (typically 3 distinct clicks/drops) before bolting to the engine. Failure to do so will crack the fluid pump, destroying the unit instantly.
- Fluid Level Check Procedure: Must be performed with the vehicle level, engine idling in Park, transmission fluid temperature between 95°F and 113°F (35°C to 45°C), removing the standpipe plug from the bottom of the pan. Removing the plug with the engine off will cause severe under-filling.
- Mandatory Cooler Flush: You must perform a hot flush of the transmission cooler lines to clear out debris from the failed unit. Failure to flush will void the warranty and ruin the replacement unit.
- Exhaust Clearance: The exhaust system (catalytic converter flange and hangers) must be loosened or partially removed to gain clearance on the CT4.
Easy to get right once you know them:
- Using standard Dexron VI or older Dexron HP fluids instead of Mobil 1 Synthetic LV ATF HP (Blue Label), which causes torque converter shudder.
- Failing to program the TUN/PUN solenoid characterization data into the TCM before driving.
- Checking the fluid level with the engine turned off, leading to a severely under-filled transmission.
- Ordering a RWD transmission for an AWD vehicle (or vice versa), which are not interchangeable due to different tailhousings and output shafts.
- Skipping the mandatory transmission cooler flush, allowing old debris to contaminate and destroy the replacement unit.
Not issues with the units on this page — the manufacturer documented these for every transmission of this family, wherever you buy one. Handy for your installer:
🔎 Recommended at install: Complete fluid exchange (triple flush) using updated Mobil 1 Synthetic LV ATF HP ('Blue Label') fluid. If caught late, replace the torque converter.
🔎 Recommended at install: Update TCM to latest GM calibration software and perform a 'Service Fast Learn' (SFL) adaptive reset.
Researched from factory recalls, TSBs and OEM service data (reference unit 400-11245-5042201). Unit-specific details — mileage, condition, warranty, freight — are covered in the checkout interview.
Policies, in plain English.
Shipping & Handling
- Ships by LTL freight on a pallet — a real freight truck, not a parcel van
- Your checkout freight quote covers delivery to your door (liftgate service included for residential addresses)
- The carrier calls ahead to schedule a delivery window — someone must be present to receive it
- Typically palletized and picked up within 2–3 business days; transit time depends on distance
120-Day Warranty
This part includes a 120-day warranty.
- If the part fails within the warranty window, we'll replace it or refund per the coverage terms
- Coverage is parts-only — installation labor is not included
- Warranty covers defects — not installation errors, misuse, or damage after installation
Your pre-purchase interview reviews these exact terms with you before anything is charged.
Returns (30 Days)
We accept returns of uninstalled parts within 30 days of delivery for this part.
- Defective parts: We will replace the part or issue a refund at our discretion
- Programming: "Needs to be programmed to my vehicle" is not a valid return reason. Many modules require dealer programming — we're happy to help connect you with resources if your dealer says it's not programmable
- Return shipping: This part ships by freight (LTL) — the part price is refundable per the terms above, but shipping costs are non-refundable and return freight follows the seller's return terms. Your pre-purchase interview walks through the exact numbers before you buy
- Parts must be returned in original packaging and unmodified condition
- Poorly packaged returns that arrive damaged will not be credited
Damaged in Shipping?
Freight damage is rare — and you're fully protected when you do two things at delivery:
- Inspect before you sign — you're allowed time to look the pallet over while the driver waits
- Write any damage on the delivery receipt before signing — that one line is what makes a freight claim succeed
- Severe damage? Refuse the delivery — it goes back at no cost to you and we make it right
- Photograph the pallet before unwrapping; report concealed damage within 24 hours of delivery
We handle the carrier claim — you just help document it. Your pre-purchase interview walks through this checklist too.
Order Cancellation
Cancel before shipment for a full refund. Once the pallet has been built, a preparation charge may apply — and once the freight carrier picks it up, shipping costs are non-refundable and standard return terms apply. Your pre-purchase interview shows the exact numbers before you pay.
Expert Guides
2020-2023 Cadillac CT4 2.0L AWD 8L45 Transmission: Problems, Identification, and Used Replacement
Identify the GM 8L45 transmission in your 2.0L Turbo AWD CT4, learn what causes torque converter shudder, and know when it's time to swap in a quality used OEM assembly.
Read Full Guide →Related Trouble Codes (OBD-II)
2 matching guidesIf your scan tool is showing one of these trouble codes, this part is a common fix. Each guide explains the code, how to diagnose it, and exactly what to replace.
Miscellaneous Information
OEM Part Numbers:
Cadillac: 24290642
Other: 0NFL, 1NFL, 1NHL, ONHL
Fits Years: 2020 2021 2022 2023
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This unit ships with the selling yard's 120-day warranty. Longer plans can be requested during checkout.
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