diff locker in snow, better or worse?

[Matt DeFina]

OK, I'm currently living in Atlanta, so not much snow.. But that being said, I've heard different opinions about using a diff locker in snow.



Some say locking the differential makes the back end slide out too easily, and others say that it gives twice the traction.



What are some of your experiences?

 

[Robert Caffyn]

Don't try to go around a corner with one of those, LOL. Bob

 

[Doctor CAD]

Don't worry about it. You can go better with a diff lock, but be careful of sharp turns.



Thousands of people have diff locks and go just fine in the snow.

 

[Bill Koonce]

A locker in the snow is great if you want to do donuts all day long.



Lockers are designed for certain conditions, like rock crawling and drag racing, where you have a good reason not to have differentiation. Off-road only, really. Lockers that can be switched on and off from inside the cabin are handy for a serious rock crawler that can be driven home. But with the lock disengaged, you have a plain 'ol peg leg, and no extra traction if it rains or snows on the road.



Semi-lockers ratchet when the torque on a half shaft exceeds a limit. This can save you from a broken half shaft, but control in turns is terrible! These are off-road only too, IMO.



The most popular traction adding third member is the clutch-type "Positraction" differential. It's a standard differential with clutch packs to tie the half shafts together using friction. In a turn, the friction gives way, allowing the differential to do its job. More exotic variations that use viscous fluids of various types to do the same thing hydraulically, rather than mechanically. The net effect is the same, although exotic computer controlled units can be made to do more than a traditional "Posi".



My favorite is the invention of Vernon Gleasman, who IIRC from long lost promotional materials was tasked with building a better "push back" tug for SAC bases above the Arctic Circle, back when the US defended itself with long range bombers. What Gleasman came up with was a revolutionary new differential that uses an ingenious system of "torque sensing" gears that can divert as much as 75% of input torque to the wheel with the most grip.



This is a big deal because, aside from the exotic electronically controlled units of late, this was the first differential to get more than 50% torque to a driven wheel.



Gleasman's design is a natural for a road-going car, due to its transparent operation and lack of the bad manners that other traction adders often exhibit. It's pretty rugged, too. Just ask any soldier who has flogged a HMMWV. They're Torsen equipped front and back. So is the Subaru WRX STi. The Ford Ranger is Torsen-equipped as well. The LS1 Camaro/Firebirds came with them stock as well. And then there are the many variations of the Audi Quattro.



Eaton has offered a Torsen knock-off, known as "Truetrac". The Eaton unit is similar to the Torsen T-2. The Eaton unit has a good reputation, and has remained in production during times when Mr. Gleasman's inventions were on hold due to legal bickering.



Quaife is a British company that makes Torsen knock-offs, mainly for FWD automotive applications.



Note that Torsen differentials are true differentials if one wheel is in the air or spinning on slick ice, traction adding cannot occur. Not to worry, there is an age old trick to restore traction that hails back in the days of clutch-type differentials. Just apply the brakes enough to control the spinning wheel and restore torque transfer. With modern electronic traction control systems, your car will do this for you!

 

[Matt DeFina]

Hi Bill,



thanks for the great writeup, i actually learned something.



I specifically bought my rear Eaton e-locker for off road this summer, and hadn't even thought of using it for on the road during winter. Hence the questions on whether to even use it, if it ever does snow down here...

 

[Bill Koonce]

Hi Matt,



I'm glad that you could benefit from my studies. They say that necessity is the mother of invention, and after suffering many Chicago winters with open differentials, I found that the oft-forgotten differential is actually a very important component in most cars.



Your ELocker can be switched in and out from inside the cab, just like the better known ARB air-powered product. This gives you some level of control, which is a Good Thing. When you're on dry pavement, you'll want to switch to open differential mode so that you don't put any unnecessary stress on your axle half shafts and related components. On the road it's all about protecting your drivetrain from excessive loads that you don't normally see when driving on terrain that's lubricated with dust, dirt, mud, gravel etc.



If you do run into inclement weather, or stuff like mud on the road, go ahead and try locking it up! The reduced coefficient of friction will cause the tires to spin before an axle breaks, just like off-road. I'd stay in open mode unless/until wheelspin becomes a problem. When you hear that one wheel spinning, lock 'em up and go again. Just don't forget to unlock when you reach dry pavement.



I've had some experience driving in light snow and freezing rain in east Tennessee, which is about as close to Atlanta that I've been behind the wheel. Although I did make progress by spinning the hell out of the loose wheel, burning off the relatively thin coating), I would have used an ELocker to get up those hills if I had had that option.



BTW, a locked rear end does give you twice the traction, provided that both wheels are on equal surfaces. But if you break traction, spinning both wheels, that's worthless. In fact it can be worse with a solid axle. As you know, the torque of the propeller shaft exerts a force against the axle, causing it to want to rotate in the same direction as the propeller shaft. This is what causes the right wheel to spin first. It also slightly alters the wheels' camber, causing them to exert a sideways force, causing the axle to be pulled away from center. This effect is bad enough when you're trying to go straight, and can cause sudden loss of control in turns.



If you have a solid axle, and just can't keep traction, you may be better off unlocking, and letting the non-spinning wheel act like an anchor to keep the axle under control. In theory this shouldn't be a problem with IRS and IFS systems. But the rubber bushings that many of these use for better NVH can cause a similar effect.



If you do get snow, find yourself a nice empty parking lot, and experiment with different settings and different maneuvers. It's easier to understand by doing it than it is to describe in words.



Have fun!

 

[Bill Koonce]

"Never mind..."

 

[Johnny O]

The Ford Ranger is Torsen-equipped as well.

Only the Fx4 Level II Ranger.

A Torsen is probably the best limited-slip diff, as mentioned a Detroit True Trac is essentially the same thing and a little bit cheaper. For driving on snow-covered roads a limited-slip is good enough, you don't really need a locker. Auburn or Eaton, I forget, makes an a electrically controlled diff that is a limited-slip in normal operation but you can hit a switch and it locks up. Kinda pricey though, over $600.

If you know how to drive it, a limited-slip is definitely better. You just have to know to get off the gas and steer into the skid if the back end slides or stay on it and steer your way out, but you have power going to both wheels. With an open diff one tire will spin, usually the right rear, the other receives very little power but helps the back end track and stay in line.

Prior to my '08 Trac I had two Rangers and a Gen 1 Trac, all 4x4's with limited-slip rears, all of them were total beasts in the snow. Besides living in PA, for 10 years I regularly drove back and forth to upstate NY to see my kids or pick them up, often in truly horrid weather and never had a problem other than visibility. Gen 2 Tracs have traction control instead of a limited-slip option, and in snow my '08 is, at best, adequate. Mostly I turn the traction control off and lock in 4-Hi because I don't like how all the automatic crap jerks it around when you're not expecting. So then I have two open diffs when I was used to having a better setup before.

To answer the original question since I ran off on a tangent, a locker in snow is good if you know how to drive it right, but besides the rear possibly sliding out it will push the front end on corners too and I'm talking rear lockers, not a front. A front locker, on road, in snow, is nearly undriveable. Everybody in my truck club with front lockers also has hubs and they will leave one unlocked when driving in snow. Otherwise it's pretty much going to go straight when you turn the wheel and into that utility pole, parked car, guardrail, or whatever.

 

[Bill Koonce]

I've heard the vendors tout electronic controls as "the best", and I've heard pundits say that they're too slow to respond and disconcerting when they kick in. I'm with the pundits on this one. There's nothing faster to respond than a fully mechanical unit, and the Torsen exhibits no clunks or other distracting behavior. When used in conjunction with electronic traction control, the Torsen tends to catch the upsets and smooth them out before the traction control system starts to rumble.



We all know that Ford was more concerned with the fallout and CYA from the roll-over accidents when they designed the Gen2. Some of the changes were great for the ST. Others not so great. And some omissions, like a traction adding differential option, were disappointing IMO. At least Ford has the aftermarket parts to let the owner DIY it into a better package.

 

[Chad Merry]

Have a powertrax locker in my ST for about 4 years now. Works perfect for me in snow, rain, sand, mud, rocks whatever I drive through.