Limited Slip vs. Locking Differentials: Which Do You Need?
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A limited slip differential shares power between both wheels so you keep traction on wet, snowy or loose surfaces without changing how the vehicle drives, while a locking differential forces both wheels to turn at the same speed for maximum traction off-road. Most daily drivers, tow rigs and winter-driven trucks are best served by limited slip, and lockers suit rock crawling, trail rigs and heavy off-road use.
How a standard (open) differential works
A standard differential lets the left and right wheels turn at different speeds in a corner, and it splits power evenly between them. The catch is that it can only send as much power to a wheel as the wheel with the least grip can use. On ice, mud or loose gravel, or when a wheel lifts off the ground, that wheel spins and the other wheel gets almost nothing. Limited slip and locking differentials fix this problem in different ways.
Limited slip differentials
A limited slip differential resists a speed difference between the two wheels. When one wheel starts to spin, it shifts power to the wheel that has more grip. It works automatically, and in normal driving it feels like a standard axle. Clutch-type units are common in trucks and SUVs, and gear-type and cone-type designs also exist.
Strengths
- Works automatically, with nothing to switch on
- Normal handling and tire wear on pavement
- A real help in rain, snow, gravel and on slick boat ramps
Trade-offs
- It may not deliver full traction when one wheel has almost none
- Clutch-type units wear over time and need the right fluid and friction modifier
- Worn clutches can cause chatter in turns or let one wheel spin more than it should
Locking differentials
A locking differential ties the two wheels together so both turn at the same speed, which gives full traction to both wheels when one has none. There are two main kinds.
- Automatic lockers lock when power is applied and release in turns. They are simple, but they can click, hop or pull in tight turns on pavement.
- Selectable lockers stay open until you engage them with a switch, cable, air line or electronics. They drive like a standard axle when unlocked. Our catalog includes electronic-locker units, such as the Ford F-150 SVT Raptor 9.75-inch and the Jeep Wrangler JK Rubicon Dana 44.
Strengths
- Full lock when engaged, which is the best traction in rock, mud and deep snow
- Selectable types give normal street manners when unlocked
Trade-offs
- A locked axle resists turning on hard surfaces, which causes tire scrub, binding and extra tire wear
- A locked front axle can make steering harder on pavement
- Automatic types can be noisy, and selectable types add parts that have to work
Side by side
| Limited slip | Automatic locker | Selectable locker | |
|---|---|---|---|
| How it works | Resists a speed difference and shifts power to the wheel with grip | Locks the wheels together under power and releases in turns | Locks only when you switch it on |
| Traction when one wheel has none | Partial, depending on design and wear | Full | Full when engaged |
| On-road manners | Normal | Can click, hop or pull in tight turns | Normal when unlocked |
| Best for | Daily driving, towing, snow, gravel | Work trucks and dedicated off-road use | Trail and rock rigs that also see the street |
| Watch for | Clutch wear, correct fluid and additive | Noise, tire wear, pavement quirks | Added parts such as a switch, air line or electronics |
Which one is right for you
- Daily driver or commuter: limited slip, or a standard axle if you rarely see slick roads.
- Towing and hauling: limited slip, which helps on gravel and slick boat ramps.
- Winter driving: limited slip handles most snow and ice. A locker helps in deep snow but needs careful use on dry pavement.
- Mud, rock and trail rigs: a locker, ideally a selectable one.
- Mixed use, such as a daily driver that also hits the trail: a selectable locker gives you both.
Already have 4WD? Four-wheel drive sends power to both axles, but a standard axle can still spin one wheel on each end. Limited slip or a locker is what fixes that.
Not sure what is in your vehicle now? Start with our guide to identifying your axle and gear ratio, or tell us how you drive and we will recommend a unit.
Fluid and additive note
Our remanufactured differentials ship without fluid because of freight shipping rules, so you add fluid at installation. The right fluid matters, especially for limited slip. Many clutch-type units need a gear oil made for limited slip use or a friction modifier added to the fluid, or they can chatter in turns and wear early.
What to use depends on your axle and your unit. Call us at 719-460-7267 before you fill it and we will tell you exactly what to use.
Frequently asked questions
What is the difference between a limited slip and a locking differential?
A limited slip differential shifts power toward the wheel with grip but still lets the wheels turn at different speeds. A locking differential forces both wheels to turn at the same speed when it is engaged. Limited slip is gentler and fully automatic, and a locker gives the most traction.
Is Positraction the same as limited slip?
Yes. Names such as Positraction, Posi and Traction-Lok are brand names or nicknames for limited slip differentials.
How can I tell if I have a limited slip differential?
With both rear wheels off the ground and the transmission in neutral, turn one wheel by hand. If the other wheel turns the opposite way, the axle is most likely a standard one. If it turns the same way, you most likely have limited slip or a locker. This test is not conclusive for every design, so check the axle tag or factory codes, or call us.
Do limited slip differentials wear out?
Clutch-type units can. Common signs are chatter in turns and one wheel spinning more than it should. Using the wrong fluid or skipping the friction modifier speeds up the wear.
Can I drive a locker on the street?
A selectable locker drives like a standard axle when it is unlocked, so it suits a daily driver. An automatic locker can be driven on the street, but expect some noise and handling quirks in tight turns.
Do I need limited slip or a locker if I have 4WD?
Possibly. 4WD sends power to both axles, but a standard axle can still spin one wheel on each end. Limited slip or a locker keeps power going to the wheel that has grip.
What fluid does a limited slip differential need?
Many clutch-type units need a gear oil made for limited slip use or a friction modifier. Our units ship without fluid, so call us and we will tell you what to use for yours.
Next step
Ready to shop? Browse our rear differentials or front differentials. Listing titles say "with Limited Slip," "with Locker" or "with Electronic Locker" where the unit has one.
Not sure which type to choose, or what fluid to use? Call 719-460-7267 or contact us and tell us how you drive. We ship nationwide from Pueblo, Colorado, and have been remanufacturing differentials and transfer cases for over 35 years. Every unit is rebuilt in-house.