Automatic Transmission Assembly for 2016-2018 Kia Optima
Product Notes Read before buying
This is a 6-speed automatic transmission for front-wheel drive models with the 2.4L engine. It ONLY fits Korea-built models, which can be identified by a 'K' as the first character of the vehicle's VIN.
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 |
|---|---|---|---|---|
| EX | Sedan | 2016 - 2018 | L4 2.4L | FWD | Automatic |
| Hybrid | Sedan | 2016 | L4 2.4L FULL HYBRID EV-GAS (FHEV) | FWD | Automatic |
| Hybrid EX | Sedan | 2016 | L4 2.4L FULL HYBRID EV-GAS (FHEV) | FWD | Automatic |
| Hybrid EX Premium | Sedan | 2016 | L4 2.4L FULL HYBRID EV-GAS (FHEV) | FWD | Automatic |
| Hybrid LX | Sedan | 2016 | L4 2.4L FULL HYBRID EV-GAS (FHEV) | FWD | Automatic |
| LX | Sedan | 2016 - 2018 | L4 2.4L | FWD | Automatic |
| EX Pack | Sedan | 2017 - 2018 | L4 2.4L | FWD | Automatic |
| EX Tech | Sedan | 2018 | L4 2.4L | FWD | Automatic |
| S | Sedan | 2018 | L4 2.4L | FWD | Automatic |
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:
- Confirm the 1st digit of the VIN is 'K' (built in South Korea).
- Confirm the 8th digit of the VIN is '3' (2.4L Theta II engine).
- Confirm the vehicle is Front-Wheel Drive (FWD).
What the install really takes — plan and budget with confidence:
Special tools this job needs:
- Engine support bar/bridge
- Heavy-duty transmission jack
- OBD2 scan tool with live data capabilities
- Fluid pump
- Torque wrench
Budget for these consumables at install:
- Hyundai/Kia ATF SP-IV fluid (approx. 7.1 to 7.4 Liters for total dry fill; 4.5 to 5.0 Liters for service fill)
- Torque converter input shaft seal (front pump seal)
- Left and right axle shaft seals (output shaft seals)
- Transmission cooler-line flush kit
- Transmission filter and pan gasket (if pan is dropped)
What your vehicle’s computers will need after the swap:
What’s involved: TCM Adaptive Relearn and Software Update
A dealer-level or advanced bi-directional scan tool is required to clear old adaptive values and perform the stationary/drive relearn. Skipping this causes immediate harsh shifting and clutch damage.
Pro tips for a smooth first start-up — hand them to whoever does the install:
- Torque Converter Seating: Ensure the converter clicks into place three times and sits fully recessed. Bolting the transmission to the engine with an unseated converter will crush the internal oil pump gears.
- No Dipstick Fluid Level Check: Fluid level must be checked via the overflow plug on the front plastic cover with the engine running and fluid temperature at 50–60°C (122–140°F).
- Subframe and Engine Support: An engine support bridge is required across the fenders because the front subframe must be lowered.
- Bellhousing Dowel Pins: Ensure alignment dowel pins are present and clean on the engine block to prevent crooked installation and bearing failure.
- Cooler Line Flush: Must perform a professional flush to clear out metal shavings and debris from the failed unit before connecting the replacement.
Easy to get right once you know them:
- Ordering for a US-built Optima (VIN starting with 5) instead of a Korea-built Optima (VIN starting with K).
- Forcing the transmission onto the engine using bellhousing bolts when the torque converter is not fully seated.
- Skipping the TCM adaptive reset and software update, leading to immediate harsh shifting and clutch damage.
- Using incorrect fluid such as generic multi-vehicle ATF or older SP-III instead of specified SP-IV.
- Skipping the transmission cooler and line flush, causing immediate contamination of 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: Inspect or swap original inhibitor switch onto the replacement unit.
🔎 Recommended at install: Replace faulty solenoid valve or internal wiring harness.
🔎 Recommended at install: Replace defective transmission fluid temperature sensor.
🔎 Recommended at install: Inspect and replace plastic valve body side cover if warped or leaking.
🔎 Recommended at install: Check and update TCM software after installation.
Researched from factory recalls, TSBs and OEM service data (reference unit 400-63228-4125079). 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
2016-2018 Kia Optima A6MF1/A6MF2 Transmission: Problems, Identification, and Used Replacement
Learn how to identify the correct Korea-built 6-speed automatic, what causes harsh shifting and solenoid failures, and when to swap in a used OEM replacement unit.
Read Full Guide →Related Trouble Codes (OBD-II)
4 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:
Kia: 45000-3BYG0RCA, 450003BYG0
Fits Years: 2016 2017 2018
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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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