No—you should not work under a car supported only by a jack. Hydraulic, scissor, and mechanical jacks can shift, tip, slip, sink, or fail. Once the vehicle is raised, transfer the load to properly rated support equipment before going underneath.
Why a Jack Alone Is Not Safe
A jack has a relatively small contact area and is designed to raise or lower a load. It can lose height because of hydraulic leakage, mechanical failure, incorrect positioning, surface movement, or vehicle movement. Even a good jack used correctly is not a substitute for secure support.
Hydraulic or Mechanical Failure
Seals, valves, pivots, threads, and other components can wear or fail. A jack can also slowly lower without an obvious dramatic failure. Under-car safety should never depend on one lifting device continuing to hold pressure.
Vehicle Movement and Slippage
Loosening a tight fastener, pulling on a component, shifting drivetrain load, or bumping the vehicle can move the car enough to destabilize a jack. Soft asphalt, gravel, dirt, slopes, or damaged pavement add additional risk.
What You Need Before Working Under a Car
- A suitable jack: Use a jack whose rated capacity and lifting range are appropriate for the vehicle and lifting point.
- Proper support equipment: Use jack stands or another manufacturer-approved support method rated for the intended load.
- Wheel chocks: Chock the wheels that remain on the ground according to the lifting configuration.
- A hard, level surface: Concrete or another stable surface is preferred. Do not improvise on soft or sloped ground.
- Vehicle-specific lifting information: Use the owner’s manual or service information to identify lifting and support points.
Jack and Jack-Stand Capacity: Avoid the Common Mistake
Do not choose capacity by simply assuming each stand must individually exceed the entire vehicle’s curb weight, and do not assume every “3-ton stand” is rated the same way. Ratings may apply per stand or per pair depending on the product and standard. Read the actual manufacturer label and instructions.
The supported axle or portion of the vehicle must remain within the equipment’s rated capacity. Vehicle weight distribution is not always 50/50, especially on trucks, EVs, vans, and heavily loaded vehicles. If you are unsure, use equipment with ample rated capacity and follow the vehicle and equipment manufacturers’ guidance.
Step-by-Step: Safe Basic Lift and Support Process
1. Park on a Hard, Level Surface
Set the transmission in the position specified by the manufacturer, apply the parking brake when appropriate for the wheels being lifted, and keep people away from the vehicle while raising it.
2. Chock the Wheels
Chock wheels that will remain on the ground so the vehicle cannot roll. The exact chock placement depends on whether the front, rear, or one side is being raised.
3. Find the Correct Lifting Point
Use the owner’s manual or service information. Do not assume a visible pinch weld, suspension arm, differential housing, subframe, battery tray, or crossmember is a safe lifting point unless the manufacturer identifies it as one.
4. Raise the Vehicle Smoothly
Center the jack saddle correctly and watch for shifting as the suspension extends. Stop immediately if the jack tilts, rolls abnormally, or the contact point begins to slip.
5. Position the Support Equipment
Place jack stands only at approved support points. Some vehicles provide separate lift and support locations; others require a specific sequence. EVs and vehicles with underbody battery packs can be especially sensitive to incorrect support-point placement.
6. Lower the Vehicle Onto the Stands
Lower slowly until the vehicle is fully supported. Confirm each stand is vertical, fully seated, and stable. Lock adjustable stands according to their design.
7. Verify Stability Before Going Underneath
From outside the crush zone, visually confirm the stands and support points. Apply a controlled stability check without placing your body under the vehicle. If anything shifts, raise and reposition the vehicle before continuing.
Should You Leave the Jack in Place as a Backup?
You may leave the jack lightly positioned as a secondary backup if it does not interfere with the work and the jack manufacturer allows it, but the vehicle must already be safely supported by the stands. The jack is not the primary support and should not carry the working load.
Are Ramps an Alternative?
Vehicle ramps can be appropriate for some maintenance when the wheels do not need to be removed. Use ramps rated for the vehicle, on a level hard surface, with the tires centered and wheel chocks placed as appropriate. Do not mix ramps, stands, and jacks in an improvised support arrangement without a documented safe method.
Never Use These as Substitute Supports
- Loose bricks or concrete blocks.
- Scrap lumber stacks.
- Milk crates or household furniture.
- A spare wheel placed as the only support.
- A hydraulic jack by itself.
Concrete masonry blocks can crack suddenly, and improvised materials may split or shift. Use equipment designed and rated for vehicle support.
Special Cases
Electric Vehicles
Many EVs have high-voltage battery packs under the floor. Incorrect lifting can damage the pack or high-voltage components. Use the exact lift points and any required adapters specified for the vehicle.
Body-on-Frame Trucks and SUVs
Frame, axle, and suspension lifting/support locations vary by model and task. Do not assume the differential housing or any suspension component is approved merely because it appears strong.
Unibody Cars
Pinch welds and reinforced pads may be designed for lifting or support, but some require adapters to prevent bending. Follow the manufacturer’s instructions.
Common Mistakes to Avoid
- Working under a vehicle supported only by a jack.
- Using the wrong lift or support point.
- Working on gravel, dirt, a slope, or soft asphalt.
- Using damaged, rusty, bent, or leaking equipment.
- Exceeding the stated capacity or ignoring whether the rating is per stand or per pair.
- Failing to chock wheels.
- Placing stands under exhaust, thin sheet metal, battery enclosures, or unapproved suspension components.
- Assuming the parking brake alone prevents all vehicle movement.
Frequently Asked Questions
Can I crawl under the car for just a few seconds with only a jack?
No. The risk exists the entire time your body is in the crush zone. Support the vehicle correctly first, even for a quick inspection.
Is a scissor jack safe for working under a car?
No. The emergency scissor jack supplied with many vehicles is intended for lifting during tasks such as a roadside wheel change, not for supporting a person underneath the vehicle.
Can I use only one jack stand?
That depends on the task and manufacturer-approved support configuration, but under-car work commonly requires stable support at more than one point. Never improvise. Follow the vehicle service procedure and stand instructions.
How do I know where to put the jack stands?
Use the owner’s manual or service information. The best support point is not determined by appearance alone.
What if I do not own jack stands?
Do not work under the vehicle. Use ramps for a task that is compatible with ramps, obtain appropriate support equipment, or have the work done by a properly equipped shop.
Bottom Line
A jack lifts the car; rated support equipment holds it while you work. Keep the vehicle on a hard, level surface, chock the wheels, use manufacturer-approved lift and support points, verify stability, and never enter the crush zone until the vehicle is securely supported.
