Transmission Assembly for 2013 Buick LaCrosse, Regal - Front
Product Notes Read before buying
This is a 6-speed automatic transmission for Front-Wheel Drive (FWD) models equipped with the 2.4L eAssist mild-hybrid engine (GM option code MHH). It has a 2.64 final drive ratio (option code FXJ). Please verify these specifications match your vehicle before ordering.
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 |
|---|---|---|---|---|
| 2013 |
| SubmodelSUB- MODEL |
Body Style | Years | Engine | Attributes |
|---|---|---|---|---|
| 2013 |
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 vehicle's RPO codes on the silver Service Parts Identification sticker in the glove box or trunk show code MHH.
- Confirm VIN's 8th digit is R (designating the 2.4L eAssist engine).
- Confirm the vehicle does not have the 3.6L V6 or 2.0L Turbo engine.
What the install really takes — plan and budget with confidence:
Special tools this job needs:
- Engine support bridge/fixture
- Transmission jack
- GM-compatible scan tool (GM MDI 2 or GDS2)
- J2534 pass-through tool
- Vehicle lift
Budget for these consumables at install:
- DEXRON-VI automatic transmission fluid
- Torque converter input shaft seal (front pump seal)
- Both CV axle seals
- Transmission cooler line flush aerosol or machine
What your vehicle’s computers will need after the swap:
What’s involved: VIN-specific programming and Transmission Adaptive Values Learn ('Fast Learn')
The 6T40 utilizes an integrated TEHCM (TCM and solenoid pack combined) located inside the transmission side cover. Because the TCM is VIN-locked, installing a used transmission without programming will result in a security lockout, communication codes, or immediate limp mode. You must flash the TCM with your vehicle's specific VIN using GM Service Programming System (SPS) software and a J2534 pass-through tool. Once programmed, you must perform the Service Fast Learn Adapts procedure using a scan tool.
Pro tips for a smooth first start-up — hand them to whoever does the install:
- Auxiliary Pump Seal Leak: Replace and lubricate the seal on the 12V auxiliary electric fluid pump before bolting the pump down.
- Torque Converter Seating: Ensure the torque converter is completely pushed back and fully engaged into the front pump gears (three separate drops) before bolting the transmission to the engine to avoid cracking the front pump rotor.
- Fluid Level Check Procedure: There is no dipstick. Check fluid level via the check plug on the side of the case with the engine running in Park on a level surface, and fluid temperature between 158°F and 230°F.
- Subframe Alignment: Ensure the front subframe is properly aligned during re-installation to maintain correct suspension and steering geometry.
- Ground Straps: Ensure all electrical ground straps are clean and securely reconnected.
Easy to get right once you know them:
- Ordering for a Non-Hybrid Vehicle: Purchasing this MHH transmission for a standard, non-hybrid 2.4L Buick LaCrosse or Regal (which uses the MH8 transmission).
- Skipping the TCM Programming: Assuming this is a simple plug-and-play mechanical swap without flashing the integrated TCM to the vehicle's VIN.
- Skipping the Fast Learn Relearn: Driving the vehicle immediately after installation without performing the Service Fast Learn scan tool procedure.
- Checking Fluid Level with the Engine Off: Removing the check plug while the engine is off, causing a massive amount of fluid to pour out and resulting in a severely underfilled transmission.
- Forcing the Transmission into Place: Using the bellhousing bolts to draw the engine and transmission together when the torque converter is not fully seated.
- Skipping the Cooler Flush: Reusing contaminated fluid or failing to flush the cooler, pumping debris from the failed unit into the replacement.
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: Replace defective internal snap ring
🔎 Recommended at install: TCM software update performed by GM dealer
🔎 Recommended at install: Complete transmission overhaul or replacement
🔎 Recommended at install: Replace worn case bushing and axle seal
🔎 Recommended at install: Complete transmission fluid flush using correct fluid, or torque converter replacement
🔎 Recommended at install: Replace the entire TEHCM/valve body assembly
Researched from factory recalls, TSBs and OEM service data (reference unit 400-04817-2801622). 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
2013 LaCrosse & Regal 6T40 (MHH) eAssist Transmission: Problems, Identification, and Used Replacement
Identify the correct MHH hybrid transaxle, understand common wave plate and TEHCM failures, and learn what to check before buying a used OEM replacement.
Read Full Guide →Related Trouble Codes (OBD-II)
11 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:
GM: 17804583, 19331887, 24251620, 24258539, 24265832
Other: 3CCW, 3JJW
Fits Years: 2013
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