How to Do a Transmission Flush at Home
How to do a transmission flush at home: drain the old fluid, flush the cooler lines, refill with a pump kit and check the level before driving.
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How to do a transmission flush starts with a plan for where the old fluid goes and how the fresh fluid gets back in. The short answer: drain or pump out the old fluid, flush the cooler lines, refill to the level your manual calls for, and check the shifts on a short drive. A flush reaches fluid that a simple drain leaves behind in the cooler and lines, so the job needs a way to move fluid, a cooler flush, and fresh fluid matched to your transmission.
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Below: the steps in order, the safety notes to read first, and the gear that handles each part of the job.
Crizendo Transmission Fluid Pump Kit 3L Manual
A 3L manual transmission fluid pump kit with a built-in pressure gauge, 8 ATF adapters and a quick-connect transparent hose for refilling through the fill point.
Pros
- 3L pressure reservoir with a built-in pressure gauge
- 8 ATF adapters for a broad vehicle fit
- Quick-connect transparent hose shows fluid movement
- Pressure relief piece guards against over-pressurization
Cons
- Manual refill system, no powered pump
- Adapters fit specific car models, not every vehicle
- Plastic reservoir rather than metal
- Refill tool only, does not flush the cooler or drain old fluid
Lubegard 19001-UNV Kooler Kleen Transmission
A 13.25 oz transmission cooler flush with a 2-in-1 fitting that clears grease, dirt, sludge and metal shavings from the cooler and lines.
Pros
- Fits all transmissions including automatic, CVT, DCT and manual
- Removes grease, dirt, sludge and metal shavings
- 2-in-1 fitting included
- Will not pollute new transmission fluid
Cons
- No warranty term is stated
- Cooler-only flush, does not replace a full fluid exchange
- One 13.25 oz bottle per listing, with no multi-pack stated
- Removes debris but adds no fresh fluid itself
Lucas Oil Transmission Fix,Bottle,Red,12 oz. 10009
A 12 oz transmission additive that can be added to existing fluid without draining any out, with no solvents in the formula.
Pros
- Can be added to existing fluid without draining any out
- Contains no solvents
- Lowers operating temperatures, per the listing
- Stops foaming, per the listing
Cons
- Title says 12 oz and red bottle; spec table says 24 fl oz and white color
- No warranty term is stated
- Additive only, not a flush or a refill tool
- Does not clean the cooler or move old fluid out
Lucas Oil 10441 Automatic Transmission Fluid
A 20 ounce automatic transmission fluid conditioner that improves shifting and reduces noise and shudder in new and older transmissions.
Pros
- Improves shifting, per the listing
- Reduces noise and shudder
- Compatible with all ATF fluids, conventional and synthetic
- For use in new and older transmissions
Cons
- Not recommended for CVT transmissions and transmission fluids
- No warranty term is stated
- Conditioner only, not a flush or a pump
- 20 ounce bottle, with no larger size stated
How to do a transmission flush: the steps in order
- Check the manual first. Confirm the fluid type, the drain and fill points, and how the level is checked. If the manual shows a sealed transmission with no fill point you can reach, book the job out.
- Warm the fluid with a normal drive, then park on level ground and let it cool enough to handle safely before opening anything. Warm fluid drains and pumps more freely than cold fluid.
- Drain or pump the old fluid out. Catch the fluid in a drain pan for recycling.
- Flush the cooler. Run the cooler flush through the cooler lines to clear the grease, dirt, sludge and metal shavings a drain cannot reach.
- Refill with the pump kit. Fill the reservoir, attach the adapter that fits your fill point, apply pressure and watch the transparent hose to track fluid movement.
- Add the conditioner if the listing allows it. Some additives go straight into the existing fluid with no drain step, and some are not made for every transmission type.
- Check the level and the shifts. Set the level exactly as the manual describes, look for leaks at every connection you touched, then take a short drive.
Safety notes before you start a transmission flush
Work with the garage door open, keep the fluid off your skin, wear eye protection and gloves, and keep a drain pan under every open line. Never run the engine in a closed garage, and never work under a vehicle that is held up by a jack alone.
Let the fluid cool enough to work with safely, and keep rags clear of hot exhaust parts. Spilled fluid on the floor is a slip risk, so clean it up.
Use rated jack stands on solid ground, wear eye protection with power and air tools, keep fuel-burning equipment out of a closed garage, and follow the manual for every tool. Read our Safety Disclaimer.
The gear that handles each step of a transmission flush
The pump kit moves fresh fluid in, the cooler flush clears the lines, and the two additives condition the fluid that stays in the box.
FAQ: garage tools
Can I do a transmission flush at home?
Yes, if your manual describes a drain and fill you can reach and a level check you can repeat. You need a drain pan, a pump kit with a fitting adapter, a cooler flush, and fresh fluid of the type your manual calls for.
Do I need a pump kit to refill transmission fluid?
A pump kit applies pressure to move fluid through the adapter into the fill point. The Crizendo kit in this guide carries a 3L pressure reservoir with a built-in pressure gauge, 8 ATF adapters and a quick-connect transparent hose.
What does a transmission cooler flush do?
A cooler flush clears the grease, dirt, sludge and metal shavings that stay behind in the cooler and its lines after a drain. The Lubegard Kooler Kleen in this guide is made for all transmissions including automatic, CVT, DCT and manual, and its listing states it will not pollute new fluid.
Can I add a transmission additive without draining fluid?
Some additives, yes. The Lucas Oil Transmission Fix in this guide can be added to existing fluid without draining any out, per its listing. Check the label on any additive first, since some are not made for every transmission type.
Can I use a transmission fluid conditioner in a CVT?
Check the label before you pour. The Lucas Oil Automatic Transmission Fluid Conditioner in this guide states it is not recommended for CVT transmissions and transmission fluids, while the Lubegard cooler flush lists CVT among the transmissions it fits.
Related: how to flush power steering fluid at home, our picks for the best oil extractor pump for transmission fluid, and the engine and shop equipment hub.
