Understanding Differences in Automotive Differentials

Hello, I'm Professor John Kelly and  this is the WeberAuto YouTube channel.   today we are looking at differentials I  have 11 different types of differentials   here on the table and we are going to take a look  at each of these some of them in more detail than   others there's a lot of similarities with some  and some pretty good differences with others   so the first differential that I have right  here is called an open differential and   an open differential is one that if traction is  lost to one of the two wheels the drive wheels   then that wheel is the one that receives all the  power the wheel that has traction gets no power   and the other wheel just sits there and spins  so let's take a look at an open differential   and then we'll compare that to various limited  slip and locking and other types of differentials   that gives power to both tires at the same  time on the same axle as this differential   so if we look at the individual pieces  of the differential this big piece right   here that rotates is called the differential  case and it has a bearing on each side of it   called differential side bearings and inside of  this differential case we have two side gears   and two differential pinion gears sometimes people  will refer to these differential pinion gears   as spider gears because I don't know we already  have a pinion gear with a ring and pinion   gear set the ring gear by the way or crown gear  for as it's called in in some European countries   would bolt to this differential case and rotate  the differential gear set so this is the second   gear set inside of a rear axle or a front axle  so let's take the gears out and take a look at   what's going on here so on this particular  model there's a little bolt that we have to undo   to remove this differential pinion pin right  here so we take this bolt out it sticks down and   engages with the pin to keep it from coming  out but as you can see when I push it out   it has a hole in it right there where that bolt  sits and that's how it's held in place but we're   just going to pull that all the way out now  when we get that pulled out all the way we have   to rotate the side gears just a little bit here   and then one on each side we can take out  the differential pinion gear on the one side   and the pinion gear on the other side  and then our side gears can drop down   here's the side gear and lift up  over here is another side gear all right this particular open differential is  out of a ford crown victoria one of my student's   vehicles where they replaced this open  differential with a limited-slip differential   okay so let's take a look at the differential  side gears and the differential pinion gears   now the side gears let's start with those first  I have brought in an axle shaft right here   and you can see the wheel studs here on the side  that your wheel and tire assembly would bolt to   and if I just set this in this little  v block here I want you to see that   the differential side gear  splines right onto that axle shaft   which means whenever you are driving down the  road it's the side gear that turns the axle shaft   it's the side gear it's not the ring gear it's  not the great big ring gear like this one right   here it's not this great big ring gear all that  ring gear does is turn the differential case. The   differential case turns this differential pinion  pin right here and that differential pinion pin turns the differential pinion gears and it  doesn't rotate the gears it makes them makes the   shaft rotate as an assembly as this differential  case rotates so as I have it oriented right here   it's just going to turn with the differential  case and as it turns with the differential case   it turns the side gears that go with  it each side gear is connected to   an axle shaft now this particular axle shaft is  called a c-clip retained axle shaft and we have   this little clip right here shim looking  piece in the shape of the letter C and   there's a groove in the end of the axle  shaft so we have to push the axle shaft up   through the side gear here and then push  the c-clip in place and then pull the   axle shaft back through the side gear and  the side gear then retains the axle shaft   and keeps it from coming out of the  axle housing as you drive down the road all right so to remove axle shafts you  have to remove the differential pinion pin   to allow them to have enough clearance  to push in and get the c-clips out and then you can pull the axle shaft  out of the side gear the side gears   sometimes will have a little shim behind  them on some axles this is a selectable   thickness shim and so you put  a shim in behind the side gear there's supposed to be another shim right  here I've lost that apparently and it   goes up inside right here the purpose of those  shims is to control the amount of backlash   this play back and forth between the  gear teeth right there so if we put these   differential pinion gears back in and it can be a  little tricky you've got to visually line them up   make sure they're straight across from each other  they also have a little washer on the back of them   to allow them to spin and stay lubricated  and reduce friction and then we'll put our   differential pinion pin back in we have  to make sure that the side with the hole is on the side with the hole  in the differential case and then our locking pin goes back in right  there so as I just explained the axle shafts   slide into those side gears and the side gears  notice they can rotate in the housing but   when you put the two axle shafts in and  put the weight of the vehicle on the ground   then you will notice one of these spins forward  while the other one spins backward so the vehicle   is not going to roll forward or backward because  these gears want to rotate in opposite directions   so instead they just lock up all right so let's  build just a little mock-up of the differential   in the vehicle itself, I've got some v blocks here  I'm just going to hook up a couple of axle shafts   another axle shaft and then those axle  shafts as I mentioned slide right into   the side gears so i'll put one  in the back here first okay   so I've got the axle shafts put into the side  gears okay notice as I turn the differential case   the side gears and the differential pinion gears  are not rotating and that's because we are driving   down the road we have equal traction and equal  load on each axle shaft but notice if one tire   breaks loose and the other tire does not I'm going  to hold this axle shaft here from rotating now   the axle shaft over here is turning faster  and it's the only one turning as a matter of   fact it turns two times faster than it normally  would if both axle shafts were rotating together   and that's because there's a formula the theory of  how this works is one rotation of the differential   case is equal to one rotation of one axle shaft  plus one rotation of the other axle shaft   divided by two so one is equal to one plus one  which is two divided by two which is one which   means one equal one is equal to one I know that's  a little confusing but let's do the math now with   one axle shaft stopped if you watch this yellow  mark right here versus this sticker right here   i'm going to rotate that housing the differential  case one time we've already had one revolution   out of that axle shaft and here comes  the second mark right there again   but we only got one rotation of the  differential case so what that means is   for one rotation of the differential case we had  zero rotations of the left-hand axle shaft we had   two rotations of the right-hand axle shaft two  or zero plus two divided by 2 is 1 which equals   the one rotation of the differential case now why  would that i mean who cares that's an engineering analysis that you would look at or design  feature it'll give you the inde it'll give you an   indication of the rotational speed of each wheel  so let's say that this axle shaft instead of being   stopped solid is rotating half of a turn so if  it rotates half a turn that means this other side   will be rotating one and a half turns so no matter  what the number of rotations of this axle shaft   plus this axle shaft always has to equal 2. so if  we have 0.5 here we have 1.5 here to equal our 2.   so you can come up with any combination that you  want there but that's how it works   so this type of differential is really  good at allowing for differences in   tire speeds that occur as you turn corners as  you turn corners the tires in on the outside   of the arc of the vehicle as you're rotating  have to travel farther and faster and so the   differential allows that to happen it allows for a  difference in the rotational speed of those tires   well this is the style of differential that's been  around since the beginning of the automobile when   they started using differentials but they've been  around longer than that but the big problem is   when you have one tire on loose a loose traction  surface and another one not on loose traction   an open differential sends power to the one  that has lost traction so for example let's   say this axle shaft is connected to a tire that  has good traction so it does it's it doesn't want   to just spin but the other one is on ice as i  turn the differential case with the ring gear   notice no power at all goes over to the tire  that has traction it sends all the power to the   wheel that has lost traction and so for  years and years and years automobiles   had this problem before paved roads were  common everywhere, dirt roads muddy roads   snow gravel whatever it may be cars would get  stuck and you would only have one rear tire   on a rear wheel drive vehicle that would  have any power to it and that caused problems   so over the years engineers tried  to come up with different ways to send power to both wheels and it wasn't until Dana  Corporation which should sound familiar to you   if you've watched any of my universal  joint videos you'll know there's one on   the history of the universal joint where  Clarence Spicer of the spicer u-joints   spicer driveline division of dana corporation  started the company and then there's Charles Dana   took over and as a business manager and ran the  company and ran it for many many years and they   named the company after him a little bit later  but dana corporation out of toledo Ohio in 1956   released a limited-slip or they  call it a locking differential for use in automobiles and so the very first   vehicle to use it was a 1956 Packard and  they called it a twin traction differential   it cost an additional 35 to 50 depending on the  vehicle and then in 1958 that same differential was used by almost everybody else so Chevrolet  picked it up and calls it positraction Pontiac   picked it up and called it safe track Studebaker  and Packard called it twin traction Chrysler   called it sure grip American Motors called it the  power lock and Oldsmobile called it the anti-slip   ford offered it in some Lincolns, I don't  know what they called it in the Ford   but this is out of a new york times article  from 1958 talking about this amazing invention   of the locking differential so the rest of  these differentials that I have here are not   open differentials they are different methods  of trying to send power to both wheels under   varying conditions using different mechanisms  so let's take a look at the version that dana   came up with and this may not be the exact  1956 version but it's it's pretty close to   it so let's take a look at that next okay our  next differential right here is from a 1965   Chevrolet so this would be what Chevrolet called  positraction and this was only let's see 1958 so   that's eight years after the invention from dana  corporation of the locking differential as they   called it now the name locking differential is  misleading it doesn't lock the two tires together   it comes close to locking them together but  it does not it allows for a limited amount   of slip hence the term later on at limited slip  differentials so let's take a look inside of this   differential case this differential case  splits in half on any differential case that   splits in half you better make an alignment mark  because it has to go back exactly where it was   and so I'm just going to take the bolts out  there loose then we'll lift the upper cover off looks like this then I want  you to see that we have a steel plate with tabs on the outside of it these little tabs  right here and then we have a steel plate with   teeth on the inside of it and then another one  with tabs on the outside and another one with   teeth on the inside and these fit all together  in what's called a clutch pack clutch pack   and that slides onto this little piece that the  side gear fits into so the side gear is right here   riding inside of this little cup and then we've  got this clutch pack on the outside of it here   on the clutch pack these little tabs these grooves  fit down into these notches in the differential   case which means that as the differential case  rotates these plates with the notches also rotate   but the gear the little cup with the gear  in it doesn't rotate with those notches   it rotates with the little clutch  plates that have the teeth on the inside   and the way clutch packs work is if we can squish  these together then they will turn as one assembly   but if we're not squishing them together  then they can rotate relative to each other   okay so we've got a differential  side gear with a clutch pack then we have four differential pinion gears this one is  missing one I only have three can't find   the fourth one but the more differential  pinion gears you have the stronger   this differential is because if we go back here to  the open differential just for a moment these two   side gears have to transfer all of the power all  of the torque from your high-performance engine   and haul that big heavy vehicle down the  road one tooth at a time so if we just had   one differential pinion gear, there'd only be one  tooth transferring that power by having two pinion   gears there are two teeth transferring the power  by having four pinion gears there are four teeth   transferring the power and so on the more  you have the more power it can handle and   then on the other side of our differential case  here let me just turn it over and dump it out there we go we have the opposite side clutch pack  and side gear just like we had on the other side   now one other thing I want you to see is that ins  in the center of this side gear, it has splined   teeth and then the center of this little cup that  holds the side gear it also has splined teeth so   when you put those two together you have to line  those splines up in order to put the axle shaft in   this old-style didn't use c-clips it had bearing  retainers on the outside of the axle instead   but you've got to line those up  before you put it back together   or you'll never get your axle shafts back  in as I found out the hard way years ago   so what are these clutch packs for what do they  do well let's take a look at just one side gear   and one differential pinion notice  they have beveled teeth there's quite a   slant to the gear tooth and as these teeth rotate  relative to each other they want to push apart   from each other they push themselves apart so  let's build the clutch pack with all the gears   without the differential case being involved  so we'll put the differential pinion gears in just like that and then the other side gear just  like that and then the other cup and clutch pack   so now as you're driving down the road and both  left and right axle shafts have equal traction   this entire assembly rotates as one  piece there's no rotating of the gears   relative to each other but if one tire  lost traction notice that that would cause   the differential pinion gears to rotate and as  those gears rotate they push apart from each other   so if we pick this up and look at it  from a side view here as this rotates   it pushes apart it pushes apart it  squishes these clutch packs together   as they squish together they try to lock the  differential case with these tabs here to the   side gear which is the clutch plates that have  the teeth on the inside of it so that tries to   connect all of them together as one big assembly  and it sends power to both axles rather than just   one and so one more time these clutch packs  this was the invention these clutch packs   aren't used unless there is a difference in  rotational speed between the left and right axle   shafts and then they get applied by the gear teeth  profile causing the gears to push apart and they   force those clutch packs to apply now that's only  going to work if the backlash the amount of play   in between the gear teeth is set properly so  sometimes there's an additional shim in here a   backlash shim that is in a selectable thickness  shim that you will go in and put in place you'll   assemble the differential case and then you'll  measure the backlash with the dial indicator and   if the backlash is too excessive then as the gears  push apart and try to apply the clutch packs they   won't have enough distance to push and the clutch  packs will slip and it won't send power equally to   both left and right axle shafts if the backlash  is too tight then it might be always applied   to where you turn a corner and it's it's dragging  the tire around the outside tire as you turn is   turning the same speed as the inside tire so it's  skidding and dragging and turning at the same time   as the inside one so that can cause these clutches  to slip and grip slip and grip cause a chattering   sound as you turn corners and so differentials  that utilize clutch packs like this require a   special lubricant and there's a limited slip  additive or lsd additive as you'll see on some   gear oil containers if you have a limited-slip or  clutch style differential then chances are pretty   high that you need a limited-slip additive to keep  them from chattering when you're turning corners   okay so this was the invention to get these clutch  packs that will apply automatically when there's   a difference in rotational speed of the two two  tires the hook to that axle but what's neat is   that once both tires both axle shafts are turning  the same speed the clutch plates release and then   if the backlash is set right as you turn corners  there's no chattering it just acts like an open   differential as you turn corners at low speeds but  then it acts it tries to lock the two axle shafts   together but it never totally locks them together  there's actually a test where you can take a   torque wrench and a special adapter and put it out  on the axle shaft and push down and measure how   much torque it takes to break away the clutches  to not break the clutches but make them slip   and most of them are around 250 pound-feet of  torque 300 pound-feet of torque for the breakaway so there's a test for these  and they do wear out   all right so this is the original  style limited-slip differential   let's get it out of the way now this is a little  bit newer version of the same thing it has a one   piece instead of a split differential case and I'm  not going to take it apart I want you to see that   right here are the clutch plates so at first  glance this may look like an open differential   but if you see those clutch plates then you  know that it is some sort of a limited-slip   or all those other words that i read off of  that new york times article one of the most   popular ones was positraction. when I was a  kid, we didn't know that Chevrolet was the only   one that used the term positraction we just  use the term posi, does your car have a posi? and   it's not very cool unless your car has a posi ,so thats posi for positraction. all right so that's   here's just another example with clutch  plates here's one out of a 1984 Corvette   and if you look right down here under the  side gear you can see the clutch plates of the positraction in the 1984 corvette then   this one i purchased from eaton corporation i  bought it about 10 years ago it's a brand new   never been used this one they actually call  the Detroit locker or posi as I've mentioned   and it not only has the clutch plates that  that you can see sticking through the top here   you can see the you can see the  clutch plates through the holes here   but this one has what's called preload springs  right here preload springs and so what that means   is that these springs right here are pushing the  side gears apart as far as they can but without   totally applying the clutch plates they're just  slightly applied and that forces the backlash   to its maximum in between these gear teeth here  which gives a quicker reaction time when there's   any type of a slip we don't have to push out on  the side gears to apply the clutch backs they're   already pushed out taking up all the play that  was in the clutches now we just push out and apply   with a variable load depending on  the difference in speed there   the the clutch plates now this is the type of  axle that we had in our cars as kids back in the   70s and to get that out to get those springs out  of there and they're pushing the springs are   pushing on two plates that push against the side  gears that's hard to get out you're getting   in there with pliers trying to squish it down  and later on when zip ties became strong enough   you could squish it down get a strong zip  tie in there and it would hold it compressed   but there was actually a special tool I've got one  right here that reaches in and grabs the spring   and then you tighten this down  and it'll compress the spring down   and you can take the spring out but this one must  have been for a little smaller diameter springs   on an older axle than on this newer one  here but this one can still reach in   and grab the top and bottom let me  turn this around so you can see it   the top and bottom of that plate and then squish  it down enough to get some zip ties in there   and pull it out so we've got two springs on  the front and two more springs on the back   these are very difficult to get apart  very difficult to put back together   and if you don't get your backlash said just  right you got to do it all again but this   is one that you can still buy today as a  replacement for an open differential or another type of differential that we'll take  a look at later that comes in a lot of general   motors trucks called the eaton locker which is  also a misleading term it doesn't lock the tires   left and right tires together it does something  else but we'll take a look at that a little bit   later so we've taken a look now at three different  clutch style limited slip pause attraction   whatever term you want to use they're all this  they're all working the same differentials and   the fourth one the old original one from 1965  Chevrolet all of these were based on that original   dana 1956 release of their invention to the  automotive industry now I've got another one   right here I want to show you because this one is  worn-out I want to show you clutch plates that are   that are worn out so this came out of  a 2010 Chevrolet Camaro super sport   this was one of my students Camaros  and apparently, it started having a one   tire burnout instead of two and so the student  decided he wanted to change gear ratios anyway   and put in a different style of differential  that didn't wear clutch plates out like this   as some people call it a Torsen limited  slip differential but it uses gears instead   of clutch plates to do the same thing I've  got one that's similar to that over here   a detroit true track but let's let's take this one  apart this one also has a split differential case okay in case you're wondering  yes I did make an alignment mark   right here on the two case halves you should  also make an alignment mark if you're going to   remove the ring gear from the differential  case but we are not so let me lift up the differential case notice the inside of  it looks very familiar looks a lot like that   origin or that old 1965 version  okay we have a side gear   two differential pinions and another side gear and  behind each side gear is a set of clutch plates   so we have the shim that controls backlash  notice this does not have teeth on the outside   or the inside then we have a clutch disc right  here with teeth on the inside notice its metal   on one side and has clutch fiber material on  the other but it's almost totally worn off and then here's a steel plate that has  these little notches on the outside that   spline into the case differential case and  then here is a double-sided clutch disc that   almost all the clutch materials are worn off of  this side and a lot of it worn off of the other   side and then another steel plate and then a  dished like a cereal bowl a spring that puts   a little preload its kind of like those big heavy  springs in that last axle that we just looked at   so this is really worn and that's because this car  was driven quite aggressively so as there was a   little bit of slip from left to right depending  on the traction of each tire these clutch   plates with the splines on the back of  the side gear whoops got upside down here the steel plates with the notches  rotate with the differential case   but then the steel plates with the clutch fiber  material rotate with the axle shaft and so   as the gears teeth push themselves apart and  try to apply this eventually all that material   wore off and it no longer functioned properly  as a limited-slip differential okay so that's a newer version of the exact same  thing let's get that out of the way   for a moment and let's move on  to our next style of differential this one also came from one of our students   that he had a and still has I think a  2005 jeep wrangler unlimited rubicon   with a rear air locking differential and he was  out four-wheeling and broke his differential   and it broke because of the off-roading he was  doing big tall tires put a lot of extra strain   on the axle shafts and the side gears down inside  of the differential case so this is an air locking   differential so let's take it apart and see  what's unique about the air locking portion here okay I've got the bolts out of it notice  I've got an alignment mark right here for   the upper and lower halves and I'm going to  lift up the upper half here we go now this has a kind of a dog tooth mechanism to connect the equivalent of a side gear but notice this has  broken teeth on it from the extreme off-roading   that this student did and instead of a clutch pack  behind the equivalent of the side gear here it   has this toothed wheel and another toothed wheel  this upper one has these four tabs that stick up through and rotate with the differential case so  it rotates all the time with the differential case   this one only rotates with the axle shaft and  then there's a spring that goes in between them   so if we lose traction then we use compressed air  to push this set of teeth into this set of teeth just like that locks it together and then  there's a spring that pushes it apart   when we don't need it applied and that  spring is right here so let's set the the apply plate right here that that gets squished  with compressed air, there's a little plate   right here that sits on these four tabs on the  outside of the differential and then there's   this piston assembly here that if I were to  get some compressed air don't put it on that   fitting right here or it'll pop the piston  right out but keep the compressed air   back several inches and just blow it in  there this will push outward and it sits   right here so in compressed air is applied to that  piston it pushes down and locks the gears together   so that's the air locker but the original  differential that came in the jeep rubicon   only had that on one side you can buy extra  heavy duty ones which this student did   and put in his jeep that has lockers or locking  teeth on both side gears rather than just one   side gear but if you lock up one it still  works but if you lock up two then the second   axle shaft is also locked directly to the  case without the torque having to go through   the differential pinion gears now another  unique thing besides this being a locking   differential is that this is also a  torsion differential so if I turn this over this gear right here that I said was the  equivalent of the side gear looks nothing   like a side gear, it's the gear teeth are  straight up there's no angle to it at all and it meshes with some other gears that are  in here so this is called the torsion   style differential the torsion  company doesn't even exist   anymore it's been sold and bought by different  companies but everybody keeps calling it torsion   but there's another side gear of  course one for each axle shaft  so we'll pull the cover off the other side  and we've got four more gears right there   right there okay I've got this Torsen differential  disassembled notice it has some strange holes   in it this differential case and that is  for all of these gears right here we've got   some short gears and then we have some  long gears and then we have our two   side gears that the axle shafts you can see  the splines inside of them that the axle shafts   sit in and then to keep these side gears from  slipping relative to each other when you lose   traction we use these long gears and short gears  and so let me turn this over we're going to have we're going to take four long  gears and they will contact the side gear on the top in my example  here and they are evenly spaced   and then we have the shorter gears here and they  come in and contact the long gear on the bottom   but also the opposite side gear on the bottom and then as one gear tries to  rotate relative to the other one   these gears the short gears versus the long  gears tend to want to push themselves apart and   away from each other so both side to side  and up and down they tend to want to push   and that makes them wedge in place inside of the  bores that they sit in which slows them down and   makes the entire assembly turn as one piece so  it mimics what the limited-slip clutch plates do   except it does it with gears and it's quite  an ingenious invention it's been around like I say   for quite a while and it shows up now and  again in different vehicles, it's pretty common in   high performance vehicles today because the clutch  pack style design doesn't seem to be strong enough   for the super high torque and horsepower of the  vehicles of some of the vehicles of today okay so   this is a torsion style limited-slip differential  since it does not use clutch plates it does not   need limited slip additive it just uses  regular gear oil or whatever they were,   not regular gear oil, nothing uses a regular gear  oil look in your owner's manual to determine   the correct type of gear oil that goes in your  differentials and transfer cases and so on   because it impacts a lot of things including your  fuel economy all right so that is quite an amazing   differential assembly not only do we have a very  high tech torsion limited slip but it's also an   air locking differential so that's pretty  cool and that's in the jeep wrangler rubicon and   that's from one of my students I have three  students the open differential thank you Jake,   the worn-out Camaro differential thank you, Cade,  and the Jeep rubicon differential thank you, Jacob they work great for these demonstrations  all right the next differential I want   to show you is a Toyota version of a locking  differential this differential has four pinions   four differential pinions so it's pretty strong it  does not use clutch plates so it acts as an open   differential normally but if you want it to lock  up solid and by the way when we have an air locker   like that jeep rubicon differential we just  looked at it truly is a locker it locks   the left and right axle shafts  together there is zero room for slip   and if you try to force it to slip bad  things can happen like broken gear teeth or give it too much power or whatever it may be  so this acts as an open differential we can look   right here on the side and this is one side  gear it has a bunch of splined teeth and then   we have this sleeve right here has teeth  on the inside, it has teeth on the outside   and this sleeve can go all the way down  in and that forces the left and right side gears to rotate with the differential  case but if we pull it out just far enough   then it becomes an open differential  again so this is an open differential or   a locking differential there's a clutch  fork as you can see in this photo right here   that slides into this groove and has an  electric motor that moves it out or back in   so instead of it being an air locker like the jeep  rubicon one that we looked at this is an electric   locking one now there's also an electromagnetic  locking one that moves similar devices that cause   either an open differential to turn into a  limited slip or to take a limited slip and   make it a locker or make it open differential  into a locker, there are all kinds of combinations   but this is what Toyota did on the Tacoma and   and other vehicles that to just make a  quick transfer into a locking differential   typically I believe this was only available in  four-wheel-drive low correct me if I'm wrong   and it had a front locking differential a rear  locking differential and a transfer case that   would lock as well so under certain conditions  for maximum traction, you get all four wheels   turning the same speed with no slip at all on  on any of them so that's another locker this   differential is called the detroit true track  and it is nothing more than eaton's version   of the torsion differential so let's just  hurry and take the cover we'll just take   off one cover and look at one side both sides  are the same so you can see down inside here   a little closer view here's  our side gear right there   and then so there are three  sets of gears on each side gear   there are not long and short ones so that's  different than the then the torsion but they do   intertwine the inner mesh the ones in the bottom  mesh with the ones on the top they push themselves   apart and up and down to wedge themselves in  place to stop the left and right axle shafts   from spinning at different speeds so this is  just another version it works very well of the   Torsen limited-slip differential except it  is actually different although it looks a lot   alike but it's called the eaton true track this  differential when i bought it eight years ago was   probably 800 which is a pretty typical price for a  brand new differential back then I haven't priced   one of these this year to see what it is but  anyway that's another option that you have   speaking of locking differentials you can  purchase for off-road or racing purposes   something called a spool and a spool would  look like a differential case like this   except without any rotating differential gears it  would just have the splines for the axle shafts on   each end now if you look at this photograph right  here we use a spool in the front power transfer   unit the ptu in an all-wheel drive crossover suv  there's no differential gear set at all it's just   one turn of the ring gear of the differential  case gives us one turn of each axle shaft   but that's a different story but you can  also buy something called a mini spool   and a mini spool let me just show you this  let me see if it'll actually fit in this ford   differential with a mini  spool take out your existing differential pinion gears and side  gears and then this piece right here   replaces the side gear so it has the same  splines but no teeth and so it comes and fits   inside in place of the side gear just like that  and then there's another one that you would put in   the opposite side this one is for a Chevrolet and  I've got a forward axle here but it would go in on   the other side and let me show you how it works on  the outside here once you get the two side gears   in place then you would slide the equivalent of  your differential pinion gears in just like that and then you take your pinion pin and put it  through and lock it in place and once that's done   this entire unit spins with the differential case there are zero gears to allow any rotation  and you've just turned your limited-slip   differential into a spool and it's quick fairly  quick and easy to do of course you have to   take your axle shafts out to do that so it'd  probably take you half an hour to swap this   out and put it back together but that's a quick  easy way and that's a lot better way than welding these gears together because once you weld  these you're done there's no one doing it plus a   welding cast iron like this takes a specially  trained welder special procedures and it's just a   bad thing to do welding a differential i know  it's it's a cheap easy way to get yourself a spool   but then you've got zero slip and if  you're driving that on a public street   you're gonna be wearing your tires out  super fast and you're gonna hate it   for the most part, all right so that is a mini  spool you can also buy just a full-size spool   all right now our very last differential to  look at is used in or has been used and still is   in general motors products since i believe  1967 if you get a general motors a gmc or a   chevrolet truck that a rear-wheel drive you  will get if you order the upscale package   you will get an eaten locker or you will get  an open differential that's all there is to it   so if you order the limited-slip differential  you receive this differential right here   called the Eaton locker now I'm not  going to take this eaten locker apart   it would take as long as this video is already  to take it apart and put it back together but   it is serviceable it must be set up properly but  let me just explain the basics of the eaton locker   if the Eaton locker is set up properly  this acts just like an open differential   the majority of the time you're driving so that  means it does not need limited slip additive   this just drives around like an open  differential there's no chattering of   when you turn corners but once there is a 100  rpm speed difference between the left and right   rear wheels then this little shaft right here  called the governor has these little spring-loaded   flyweights that fling out and as it rotates they  fling out and it can grab this piece right here   and lock the two together and then there's  something inside called a ball ramp   that will rotate and apply the limited-slip clutch  pack it has clutch plates on the left and right   side gears so think of it as one of the old school  differentials limited slip differentials except   it has this switch call the governor that  can switch it between an open differential and a   limited-slip differential so it's the best of both  worlds it really is a nice differential it's not   super heavy duty so if you're into rock climbing  and off-road four wheel drive whatever this   probably isn't going to last a super long time  for you but it it'll work as long as you don't   give it shock loads it'll work just fine but  so one more time this is an open differential that   suddenly can be switched to a clutch plate style  limited-slip differential which is pretty cool   there's a special tool right here to come in and  remove some press pins and get these governor   and flyweights out of here and then there's a  spring or there's a big block in there in between   the two side gears to transfer the  clutch apply pressure to each side gear   because the apply pressure only comes from  one of the side gears so it has to transfer   through into the other side gear through  this block comes in different   thicknesses when you put this together you've  got your you got to set your backlash properly   there's a different backlash for the left side  gear versus the right side gear and once your   backlash is set right you take a a tool and  measure the distance between the two side gears   and subtract a certain amount and that's the  thickness of the block that you put back in there   so hopefully someday I'll do a video on the  complete disassembly and reassembly of this   i'm just out of time this week to do that  for my students but it it can be done   you don't have to replace the entire  thing although trying to find parts   might be might be a problem i had a student here  years ago that tried to rebuild one of these and   it took quite a while for the Chevrolet dealer  to be able to get the repair parts that he needed   okay so to wrap up here we learned that the first  limited slip or posi differential was developed by   dana corporation and released in the first vehicle  ever in 1956 and has been used ever since there   are clutch plate-style limited-slip differentials  there are the gear style we've got the torsion   style limited slip we've got the  Detroit truetrac style limited slip   we've got locking differentials that are  electrically locked we've got air locks   we've got on older vehicles there was a cable  a mechanical lock that could occur on to   to engage those they all have the same goal in  mind as to give you ease when turning corners   like an open differential but then engage and  not totally lock up but almost totally lock up   when you lose traction and then disengage again  the only ones that don't disengage are the spools   the mini spools or if you've welded your  differential side gears to your differential   pinion gears um and that as a as i said i think  you'll regret that eventually all right well um   that took a long time we could spend a lot more  time on differentials but we've talked about   11 different ones and advantages and disadvantages  to each of these thank you for watching

Channel: WeberAuto

Views: 702,622

Rating: 4.9150863 out of 5

Keywords: WSU, Weber State Automotive, Weber State University, John D. Kelly, Guy in Wheelchair, Professor Kelly, EV Boot Camp, Utah, Layton, WSU Davis, Weber State University Davis Campus, Differentials, Eaton Locker, Positraction, Mini-Spool, Spool, Detroit Truetrac, Tacoma, Electric Locker, Torsen Differential, Air Locker, Limited Slip, Open Differential, Differential Equations

Id: 1a9JQC6fgXw

Length: 63min 13sec (3793 seconds)

Published: Thu Jan 28 2021