BigJ
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FRF member Chrisandalex1 put me in contact with the folks at Wavetrac. They're in the process of adapting their differential for the Raptor, and they invited me in for a behind the scenes look at their facility, the 2012 Raptor front SVT and Ford sent them, and at how their differential is different. The following is my thoughts on what I saw.
First and foremost to follow along in all this, ya kind of need to understand what a differential is. If you're curious and motivated, definitely study up on the subject. There are some great easy to understand discussions quickly found with a Google on the subject. It really is a neat and interesting science and people make careers out of differential design and implementation.
But for the sake of this post lets just think of our diffs as the boxes that take power from the engine and gearboxes, and actually puts it to the tires. Its the box in the middle of your axle(s), that takes the spinning driveshaft and converts that motion and power into spinning tires. For this discussion, that's about as technical as we need to get.
Our Raptor's have two differentials; one in the rear and one up front. In the rear, we all have open differentials that can be locked. What this means is that normally (when open), the diff lets each wheel spin at a different speed. For on road driving this a great thing as it saves wear and tear on components and tires, and provides for a smooth ride. Picture what happens when you go around a turn... the outside wheel has a much further distance to go in the same amount of time that the inside wheel has to go a less distance, so the outside needs to spin much faster! If it didn't you would quite literally "hop" around a turn as the rear of the truck skips and slides.
But what happens when you go off road? What happens when you end up on two different surfaces? Like, for example, what happens when one tire is up on a rock, and the other is on sand? With an open differential, the wheel on sand will end up spinning at full speed, and the wheel on the rock might not spin at all.
So, enter the locking differential. When you pull our or knobs and "lock" the rear, you've now commanded the rear differential to "lock up" and basically become one solid bar, forcing it to spin both wheels at the exact same speed. In the example I just gave, this would result in the wheel on the rock spinning at the same speed as the wheel in the sand, and therefore you start moving again.
Clear as mud? Ok then...
Now consider the front differential. All the same concepts apply up front as they do in the rear when our Raptor's are in 4 wheel drive. However, unlike the rear, Ford didn't give us the option of a "locker" in the front. We don't have a knob we can pull and lock 'er up. In fact, in the 2010 and 2011 Raptors, all we have is an open differential which really means that when we get in the soft stuff or get a tire in the air (again different surfaces under each tire (air and ground in this case)), us OG's end up right back in 2 wheel drive (right? You're with me on that? Even though we're in 4x4, lets say one of the front wheels is on sand and the other front wheel is on rock... the wheel in sand is spinning at full speed doing nothing, and the wheel on rock isn't spinning at all also doing nothing... therefore the only wheels doing anything are the rears... aka 2wd?)
Recognizing this limitation, Ford gave the 2012+ Raptor a "limited slip" differential, made by a company called Torsen. What's a limited slip? Think back to the open diff, and how it lets each wheel spin freely... a limited slip diff tries to recognize that one wheel is spinning almost freely and the other isn't moving. It tries to send speed from the freely-spinning wheel back over to the stuck-not-spinning wheel in hopes of making it move. It, basically, tries to a point to make the wheel with traction actually move automatically and on the fly.
The how's and why's of the decision Ford made to go with a limited slip Torsen are, again, beyond this discussion. For our purposes, the bottom line is that's what Ford decided to give us and so here we are. And, honestly, when coming from an open diff like in the older Raptors, a Torsen is a revelation. It makes it so that almost all the time you end up with at least some power going to the wheel that needs it the most, and less power going to the wheel that's spinning. Those that have driven Raptors with and without a Torsen say its a night and day difference in the dirt.
But... it could be better. By a lot. A limited slip differential isn't perfect in that when that free spinning wheel actually ends up with freely spinning, it cannot apply power to the non-free-spinning wheel. In other words, as the speed differential between the wheels increases the limited slip diff tries harder and harder to put more power to the non-free-spinning wheel, right up until the difference between the two is too great, and it can't try any more. Once that happens, it acts exactly like an open diff and we end up right back where we started.
The best way to visualize this is when one tire is up in the air. In that case, the open diffs in the 2010 and 2011 and the Torsen in the 2012's will act exactly the same. BUT wait! We can introduce a restriction into that spinning in-the-air wheel, can't we? What happens when we lightly press the brake at the same time we're giving it gas? Can you picture it? Now, all the sudden that Torsen can do its job. It sees that the wheel in the air isn't actually freely spinning any more, and NOW it can sent power to the wheel still on the ground and in theory now you can drag your sorry butt out of the hole.
The 2012+ Raptors will do the braking for you. The computer will see all this happening, and figure out that it needs to brake the spinning wheel so the Torsen can work. Us 2010 and 2011 guys will need to work the brakes ourselves. But again, either way, upgrading to the Torsen for this purpose and in this regard is a great thing according to those who've driven with and without.
So where does the Wavetrac come in? It takes that braking requirement / tire-spinning-in-the-air issue of a limited slip differential, and kills it dead. The Wavetrac itself figures out what's going on with each tire, and sends power to the more planted one automatically just like the Torsen, but unlike the Torsen there is no "give up" point with the Wavetrac. The Wavetrac will *always* apply power to the more planted wheel, no matter if the other one ends up totally free spinning or not.
And as I understand it, that right there is the number one reason to choose a Wavetrac. There's no braking system / driver input needed. There's no give up point. There's no 4x2ing when in 4x4.
So how does it do this? Again that's probably too technical for this discussion. Those with an engineering and/or diff building background looking at the vid and pics below will see pretty much right away how the Wavetrac does its thing. But for the rest of us here's the quick idea: there's a "cam" in there that pushes apart as the difference in speeds increases. This pushing action presses against carbon fiber bearing surfaces, introducing friction. In other words, the Wavetrac creates its own drag, and therefore there's never any "free spinning" wheel to contend with. I gotta say, this is one seriously innovative design.
Another advantage of the Wavetrac over the Torsen is that it won't wear like the Torsen will. Unfortunately and for better or worse, the Torsen needs to be seen as a wear item. Nobody knows yet really what that means, but for it to do what it does and how means there is metal on metal parts wearing in there, and as those parts wear, the performance will degrade. Again, nobody really knows how soon or to what extent; shoot for all anyone knows the Torsen could go 500k miles before needing to be replaced. All I'm saying is that it *is* wearing in there. The Wavetrac, basically, won't. Because of how it does its job, the wear surfaces are those carbon fiber discs, and those have a lifespan that will probably outlive you. And if they don't, send it back to Wavetrac and they'll fix it for free for life. Hard to argue with that.
Ok on to the pics!
On the left is a brand new 2012 Ford Raptor front "pumpkin" (the box that holds the differential). You can see the Torsen in there. On the right is the Wavetrac.
Torsen up close
Wavetrac up close
Pulling out the Torsen
A couple of shots of the Ford housing. Those who know castings might find this... interesting...
I don't think Ford used enough
Back in the lab, taking apart a Wavetrac for show and tell
Here's the "cam", that makes the magic happen. See the black part in his right hand? See how its seated in the silver part in his left? This is how it is when you're on the street; this is "open".
Now see how that black part is riding up the silver part? This is what happens when one of the wheels starts to spin faster than the other. The "cam" rides up, basically pushing against a part that doesn't want to move... there's your friction... there's your resistance. That's what causes the Wavetrac to not let a wheel spin freely and instead keeps pushing speed over to the wheel that actually has resistance... aka traction.
Blown apart
First and foremost to follow along in all this, ya kind of need to understand what a differential is. If you're curious and motivated, definitely study up on the subject. There are some great easy to understand discussions quickly found with a Google on the subject. It really is a neat and interesting science and people make careers out of differential design and implementation.
But for the sake of this post lets just think of our diffs as the boxes that take power from the engine and gearboxes, and actually puts it to the tires. Its the box in the middle of your axle(s), that takes the spinning driveshaft and converts that motion and power into spinning tires. For this discussion, that's about as technical as we need to get.
Our Raptor's have two differentials; one in the rear and one up front. In the rear, we all have open differentials that can be locked. What this means is that normally (when open), the diff lets each wheel spin at a different speed. For on road driving this a great thing as it saves wear and tear on components and tires, and provides for a smooth ride. Picture what happens when you go around a turn... the outside wheel has a much further distance to go in the same amount of time that the inside wheel has to go a less distance, so the outside needs to spin much faster! If it didn't you would quite literally "hop" around a turn as the rear of the truck skips and slides.
But what happens when you go off road? What happens when you end up on two different surfaces? Like, for example, what happens when one tire is up on a rock, and the other is on sand? With an open differential, the wheel on sand will end up spinning at full speed, and the wheel on the rock might not spin at all.
So, enter the locking differential. When you pull our or knobs and "lock" the rear, you've now commanded the rear differential to "lock up" and basically become one solid bar, forcing it to spin both wheels at the exact same speed. In the example I just gave, this would result in the wheel on the rock spinning at the same speed as the wheel in the sand, and therefore you start moving again.
Clear as mud? Ok then...
Now consider the front differential. All the same concepts apply up front as they do in the rear when our Raptor's are in 4 wheel drive. However, unlike the rear, Ford didn't give us the option of a "locker" in the front. We don't have a knob we can pull and lock 'er up. In fact, in the 2010 and 2011 Raptors, all we have is an open differential which really means that when we get in the soft stuff or get a tire in the air (again different surfaces under each tire (air and ground in this case)), us OG's end up right back in 2 wheel drive (right? You're with me on that? Even though we're in 4x4, lets say one of the front wheels is on sand and the other front wheel is on rock... the wheel in sand is spinning at full speed doing nothing, and the wheel on rock isn't spinning at all also doing nothing... therefore the only wheels doing anything are the rears... aka 2wd?)
Recognizing this limitation, Ford gave the 2012+ Raptor a "limited slip" differential, made by a company called Torsen. What's a limited slip? Think back to the open diff, and how it lets each wheel spin freely... a limited slip diff tries to recognize that one wheel is spinning almost freely and the other isn't moving. It tries to send speed from the freely-spinning wheel back over to the stuck-not-spinning wheel in hopes of making it move. It, basically, tries to a point to make the wheel with traction actually move automatically and on the fly.
The how's and why's of the decision Ford made to go with a limited slip Torsen are, again, beyond this discussion. For our purposes, the bottom line is that's what Ford decided to give us and so here we are. And, honestly, when coming from an open diff like in the older Raptors, a Torsen is a revelation. It makes it so that almost all the time you end up with at least some power going to the wheel that needs it the most, and less power going to the wheel that's spinning. Those that have driven Raptors with and without a Torsen say its a night and day difference in the dirt.
But... it could be better. By a lot. A limited slip differential isn't perfect in that when that free spinning wheel actually ends up with freely spinning, it cannot apply power to the non-free-spinning wheel. In other words, as the speed differential between the wheels increases the limited slip diff tries harder and harder to put more power to the non-free-spinning wheel, right up until the difference between the two is too great, and it can't try any more. Once that happens, it acts exactly like an open diff and we end up right back where we started.
The best way to visualize this is when one tire is up in the air. In that case, the open diffs in the 2010 and 2011 and the Torsen in the 2012's will act exactly the same. BUT wait! We can introduce a restriction into that spinning in-the-air wheel, can't we? What happens when we lightly press the brake at the same time we're giving it gas? Can you picture it? Now, all the sudden that Torsen can do its job. It sees that the wheel in the air isn't actually freely spinning any more, and NOW it can sent power to the wheel still on the ground and in theory now you can drag your sorry butt out of the hole.
The 2012+ Raptors will do the braking for you. The computer will see all this happening, and figure out that it needs to brake the spinning wheel so the Torsen can work. Us 2010 and 2011 guys will need to work the brakes ourselves. But again, either way, upgrading to the Torsen for this purpose and in this regard is a great thing according to those who've driven with and without.
So where does the Wavetrac come in? It takes that braking requirement / tire-spinning-in-the-air issue of a limited slip differential, and kills it dead. The Wavetrac itself figures out what's going on with each tire, and sends power to the more planted one automatically just like the Torsen, but unlike the Torsen there is no "give up" point with the Wavetrac. The Wavetrac will *always* apply power to the more planted wheel, no matter if the other one ends up totally free spinning or not.
And as I understand it, that right there is the number one reason to choose a Wavetrac. There's no braking system / driver input needed. There's no give up point. There's no 4x2ing when in 4x4.
So how does it do this? Again that's probably too technical for this discussion. Those with an engineering and/or diff building background looking at the vid and pics below will see pretty much right away how the Wavetrac does its thing. But for the rest of us here's the quick idea: there's a "cam" in there that pushes apart as the difference in speeds increases. This pushing action presses against carbon fiber bearing surfaces, introducing friction. In other words, the Wavetrac creates its own drag, and therefore there's never any "free spinning" wheel to contend with. I gotta say, this is one seriously innovative design.
Another advantage of the Wavetrac over the Torsen is that it won't wear like the Torsen will. Unfortunately and for better or worse, the Torsen needs to be seen as a wear item. Nobody knows yet really what that means, but for it to do what it does and how means there is metal on metal parts wearing in there, and as those parts wear, the performance will degrade. Again, nobody really knows how soon or to what extent; shoot for all anyone knows the Torsen could go 500k miles before needing to be replaced. All I'm saying is that it *is* wearing in there. The Wavetrac, basically, won't. Because of how it does its job, the wear surfaces are those carbon fiber discs, and those have a lifespan that will probably outlive you. And if they don't, send it back to Wavetrac and they'll fix it for free for life. Hard to argue with that.
Ok on to the pics!
On the left is a brand new 2012 Ford Raptor front "pumpkin" (the box that holds the differential). You can see the Torsen in there. On the right is the Wavetrac.
Torsen up close
Wavetrac up close
Pulling out the Torsen
A couple of shots of the Ford housing. Those who know castings might find this... interesting...
I don't think Ford used enough
Back in the lab, taking apart a Wavetrac for show and tell
Here's the "cam", that makes the magic happen. See the black part in his right hand? See how its seated in the silver part in his left? This is how it is when you're on the street; this is "open".
Now see how that black part is riding up the silver part? This is what happens when one of the wheels starts to spin faster than the other. The "cam" rides up, basically pushing against a part that doesn't want to move... there's your friction... there's your resistance. That's what causes the Wavetrac to not let a wheel spin freely and instead keeps pushing speed over to the wheel that actually has resistance... aka traction.
Blown apart
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