Is a locked rear differential any less safe than an unlocked rear differential?

Question

I recently purchased an '06 Jeep Wrangler, and at the behest of one of my good buddies I purchased a Lockright locker for the Dana 35 rear differential. I live in an area notorious for extreme winter weather, ice and snow. Should I feel any less protected with the locked differential?

Answer 1

Quite the opposite -- in extreme low traction situations, a locked diff is a significant safety feature. Here's how it works.

A normal differential (sometimes called an "open differential") allows the two wheels on an axle to spin at different speeds, such as when going around a corner. Think about it: as you make a turn, the wheel on the outside is traveling much farther than the wheel on the inside, but it has to do it in the same time -- therefore the wheel on the outside turns at a higher speed.

On a dry road, this is a fine thing; it keeps your tires from wearing out. But on a wet, slippery, or icy road, sometimes one wheel will start to spin because it has no traction. An open differential can't tell the difference between a wheel spinning faster because it's going around a corner, and a wheel spinning faster because it's stuck on an icy patch. Meanwhile the wheel that has grip stands perfectly still, because the diff is doing its job of letting one wheel go faster than the other. So you sit there, whizzing one tire and going nowhere.

A locked differential disables the open-differential feature and makes sure that both wheels spin at the same speed no matter what. This way, if one wheel drives over a patch of ice, both wheels will distribute the driving force equally because they are locked together.

Now, on dry pavement, a locked differential can cause some problems -- particularly with tire wear. When you make a corner in the dry with a locked differential, the inside tire is forced to make the same number of revolutions as the outside tire, even though the path it takes is shorter. This means the inside tire is going to spin, slightly, and this will wear the tire out more quickly.

Some manufacturers allow differentials to be locked and unlocked under specific conditions. For example, my wife's Audi quattro has a switch to let us lock the rear differential; however, it automatically disengages at speeds above 15 mph. It's designed to provide the safety of a locking differential for getting started on snowy, wet or muddy roads, while still providing the benefits of an open differential once you're in motion.

Another way of letting a differential change its locking mechanism depending on conditions is called a limited-slip differential. The idea there is that limited-slip differentials use some mechanism to reduce the difference in speed between the inner and outer wheels. In practice this generally means they go around corners easily in the dry, but don't spin one wheel in the wet or snow. My Subaru WRX, for example, has limited-slip differentials in the center and rear positions, with the result being that a hard launch in muddy or snowy conditions results in instant forward motion, not a whirring sound as the wheels spin while the car stands still. (I compete in a sport called rallycross, which involves driving as quickly as possible around a tight, twisty course laid out on a grassy or muddy field, so I can do this without being irresponsible enough to try it on a public road.)

The thing to remember, though, about AWD/4WD vehicles is that they do NOT make anybody a better driver, nor do they suspend the laws of physics. They allow you to get going in conditions where other vehicles may be stuck, but AWD does nothing to help you stop in the same conditions. In the words of Peter Parker's uncle, "With great power comes great responsibility."

Best of luck!

Answer 2

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RE:
Is a locked rear differential any less safe than an unlocked rear differential?
I recently purchased an '06 Jeep Wrangler, and at the behest of one of my good buddies I purchased a Lockright locker for the Dana 35 rear differential. I live in an area notorious for extreme winter weather, ice and snow. Should I feel any less protected with the locked differential?

Answer 3

Well your in great luck. That locking differential actually increases your traction on slick roads, in mud, in snow, sand, etc. No its not less safe, actually its more safe because you are less likely to get stuck than with a conventional differential because both rear tires will be constantly spinning when the differential is locked in, where as a conventional differential if one wheel looses traction that wheel will just spin leaving you sitting there going knowhere. So you should feel more protected knowing that you have more traction available to you in bad weather. But having that great 4WD vehicle still doesn't mean to drive 70MPH in snow and ice. For some reason some people see that 4WD, or 4X4 vehicle as a ticket to not needing to slow down in bad weather, hence the offroad recovery I do every winter.

Answer 4

What Is A Locking Differential

Answer 5

With a locking differential or posi traction you will get better traction in mud or snow while going in a straight line. If it is a real posi traction be carefull on sharp turns or corners, the rear-end of the vehicle will tend to slide out away from the direction you are turning when accelerating

Answer 6

The rear end will try to swing wide at times (especially on the gas), but if you're used to winter driving that shouldn't be much of an issue.

Answer 7

Rock climbing it's the best investment you'll ever make. Regular street use and some off roading you'll have no advantage against Trucks using minimum slip.