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Mishimoto

Mishimoto 2020+ Chevrolet / GMC Duramax L5P 6.6L Transmission Cooler

4.7 store rating · 575 reviews
SKU: MISMMTC-DMAX-20

Fits 2020–2026 Chevrolet Silverado 2500 HD / 3500 HD, 2020–2026 GMC Sierra 2500 HD / 3500 HD · 6.6L Duramax

All 25 applications
$370.99
Ask us about availability. Call or text 908-223-9744 and we will get it or find you the right alternative.
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The factory transmission cooling on the 2020+ Chevrolet and GMC Duramax L5P 6.6L is sized for stock duty, and fluid temperatures climb fast under the sustained load of towing and heavy hauling. Heat is what wears a transmission out. The Mishimoto Transmission Cooler attacks the problem with raw capacity: a tube-and-fin core with a 245% increase in core volume over stock, giving the system far more headroom to keep fluid temperatures in a safe range when the truck is working hardest.----The core also adds a 137% increase in frontal area, putting more of the cooler directly in the incoming airstream, and a 173% increase in external fin area to move heat from the fluid into the air more efficiently. All-aluminum construction handles the thermal demands of stock and modified Duramax trucks alike, and the cooler retains the factory transmission line connections for a clean, complete upgrade with no additional adapters or plumbing.----Direct fit for the 2020+ Chevrolet and GMC Duramax L5P 6.6L. No drilling, cutting, or modification required. Backed by the Mishimoto Lifetime Warranty.

Installation Instructions
  • 245% larger core volume for serious heat dissipation - the oversized tube-and-fin core gives the transmission far more capacity to pull heat from the fluid under tow and heavy load.
  • Tube-and-fin aluminum core built for sustained load - durable all-aluminum construction holds transmission temps in check through the heat of towing where stock cooling falls short.
  • 173% more external fin area accelerates heat transfer - the added fin surface moves thermal energy from the fluid into the airstream far more efficiently than the stock cooler.
  • Factory connections, no adapters required - the cooler uses the OEM transmission line connections for a complete bolt-on upgrade with no extra fittings or plumbing work.
  • 137% more frontal area catches more cooling airflow - the larger frontal core area puts more of the cooler in the incoming airstream to drop fluid temps faster.
  • Drops in without modification - confirmed direct fit for 2020+ Chevrolet and GMC Duramax L5P 6.6L trucks, with no cutting, fabricating, or adapter work required
  • Own it for life - backed by Mishimoto’s Lifetime Warranty, your investment is protected long after install day.

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Good to know

Questions, answered straight.

If it is not here, call or text the counter. Real people, real answers.

Fitment

  • Will this fit my truck?

    The Fits section at the top of the page lists the manufacturer's applications for this exact part. If your year, make and model is not there, or you are not sure, text us a photo of what you are replacing with your year and engine and we will confirm it before you order.

  • What if I order the wrong part?

    Call or text us before it ships and we will swap it. After delivery you have 30 days to return it in new, uninstalled condition. The return policy has the restocking details.

Shipping

  • When will it ship?

    In-stock parts usually ship within 1 to 2 business days from warehouses across the USA. The stock line under the options tells you the status of the part you are looking at. Large items ship LTL freight and we call to schedule delivery.

  • Why did I only get part of my order?

    We ship from multiple warehouses, so an order with several items can arrive in more than one box. Tracking for each shipment is emailed as it goes out. Full details in the shipping policy.

Returns and warranty

  • What is the return policy?

    30 days from delivery, in new and uninstalled condition, with a restocking fee. Everything is spelled out in the Returns & Refund Policy.

  • How do warranty claims work?

    We are an authorized dealer, so the manufacturer's warranty applies to every part we sell. Call or text us with your order number and we handle the claim with the brand for you.

Paying

  • Can I pay over time?

    Yes. Shop Pay installments are offered at checkout on qualifying orders, and the monthly estimate shows right under the price.

  • What is a core deposit?

    Some remanufactured parts, like injectors and turbos, carry a refundable core deposit. It is shown on the product page when it applies and refunded when your old part comes back to us.

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Why buy here

A diesel shop that sells parts, not a website that sells boxes.

Every part on this site is one our own techs can stand behind.

  • We run what we sell

    A working diesel repair and fabrication shop in Nazareth, PA. These are the parts our techs install every week.

  • Real techs on the phone

    Call or text 908-223-9744 and you get a diesel tech, not a script.

  • Authorized dealer

    Genuine parts straight from the manufacturer, with the factory warranty behind them.

  • Fast from stock

    Most in-stock parts ship in 1 to 2 business days from warehouses across the USA.

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Full Send Diesel, Nazareth, PA

A team of diesel people, not a call center.

Full Send Diesel is a shop full of techs, builders and parts people in Nazareth, Pennsylvania. When you call or text, you reach someone who works on these trucks and knows the parts.

Not sure what you need? Send a photo of what you are replacing with your year and engine. We will point you to the right part, confirm it is in stock, and get it moving.

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Mon–Fri, 8am–4pm ET. After hours, text or email and we answer first thing in the morning.

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