Center Differential Transfer Cases

Hello, my name is John Kelly I'm the creator of  the WeberAuto YouTube channel and in this episode   we are going to discuss the difference between  a standard four-wheel drive transfer case and   a center differential transfer case so to begin  with I've got some a couple of components from   a standard four-wheel drive transfer case  like you would find in any full-size pickup   truck four-wheel drive and what I want to point  out as far as the difference between the center   differential transfer case and a regular transfer  case is the power flow so I've got two pieces here   this is the input shaft to the transfer case the  automatic transmission or manual transmission is   output shaft is going to come in here and send  power to this input shaft this is the output   shaft of the transfer case and it's where the  flange or the slip yoke of your propeller shaft   is going to connect and propel the vehicle so I  want to show you that these two pieces are hooked   together so here's our input shaft here's our  output shaft but I want you to see that there's   no physical connection between those two let me  zoom in here just a little bit so you can get   a better view of what's going on so we've got  the input shaft we've got the output shaft on   a regular four-wheel drive vehicle without the  center differential transfer case we have to   shift Forks one of them is called a range shift  fork and it's going to move this range sleeve   in and out to give us four wheel drive high  two-wheel drive or four-wheel drive low and   then we have a mode fork that'll move this shift  sleeve back and forth to give us the tool drive   mode or the four-wheel drive mode well let's  see how those are accomplished if we take this   range sleeve it's going to spline from this hub  this clutch hub back here to this Sun gear hub   that's part of the input shaft and it has blind  splines and so it only lines up one way on this   particular transfer case this transfer case  is out of a 2013 Toyota Tundra some transfer   cases do not have a blind spline and you can  just line it right up and get the sleeve to   fit on with no problem but this one's tricky  so you got to find the right the right teeth there we go okay so I've got that on I'm  going to put the input shaft back on it okay so we've got a range fork that's going  to come in here and it can move this sleeve   all the way back and connect the output shaft to  the input shaft and notice now everything turns   if we turn the input shaft the output shaft when  we put the flange on here so it's a little more   obvious if we turn the input shaft one turn  the output shaft turns one turn but on a lot   of transfer cases there's a neutral position  where this shift sleeve is moved to disconnect   the input shaft from the output shaft so now the  input shaft is spinning nothing's happening with   the output shaft and then there's a four-wheel  drive low range that involves a planet carrier   this particular one is a six pinion planet  carrier little bearing just fell out there   and then in the housing of the transfer case is  the big ring gear that this sits inside of this   gear right here on the input shaft is the Sun gear  and so what happens is the planet carrier sits up   in here like this whoops we're missing a piece I  have to have this piece with the planet carrier it's the front of the planet carrier that allows  that shift sleeve to connect with it there we go   that looks like I've got to put that on before the  input shaft okay so I've got the planet carrier   I'm going to get it spline to the Sun gear on  the input shaft notice the planet carrier is just   free to rotate it's a little adapter connects  to the front of the planet carrier and excuse   me has some teeth on the inside of it there that  allows this shift sleeve when the shift fork pulls   it out to this position to engage the planetary  gearset and now I'm going to have my hand pretend   it's the ring gear of the planet carrier and  roll these opinions around but if I rotate the   input shaft that's much on it okay let's rotate  the input shaft I'm going to rotate the input   shaft one full turn and let's watch the output  shaft I want you to notice that we do not get there we got a full turn right there of the input  shaft we did not get a full turn of the output   shaft as a matter of fact these gear reduction  ratios in four-wheel drive low are typically like   on this model 2.6 for turns of the input shaft  to one turn of the output shaft or 2.72 turns the   input shaft to one turn the output shaft the Jeep  Wrangler has an optional transfer case with a four   to one reduction in the transfer case for a really  low four-wheel drive low so once again this shift   sleeve here if we move it all the way in gives us  a direct connect connection input shaft to output   shaft one turn if we move it to a middle position  right here then where we are in neutral there's   no power flow and if we move it all the way out to  a third position here then we have gear reduction   taking place of two point six four turns of the  input shaft to one turn of the output shaft so   that's for low range and high range in four-wheel  drive but we're still if power is only coming in   and going straight out the output shaft that goes  to the rear axle and that's two-wheel drive so   we need to see how to throw four-wheel drive in  there so now we've got another shift sleeve and   have to pay attention to which way it goes on it  has tapered teeth on one side flat teeth on the   other we want the tapered teeth of the sleeve to  mesh against the tapered teeth of the gear that it   needs to connect with way it completes the shift  easily this is also the shifts leave also has a blind spline this one's easier to easier to match  up so get that up on this hub here of course it's   always easier said than done oh come on there we  go alright got that on pardon me okay now I've got   the output drive gear for four-wheel drive right  here that I'm going to put on to our output shaft it's big bearing up inside of there there we go so we have that output gear on  there this output gear right here is what the   drive chain connects to and then connects to the  front output gear so we've got the front output   shaft for the from propeller shaft connected to  the chain the chain then goes around this gear   so if this gear rotates then we are in four-wheel  drive but notice right now with this shift sleeve   back or towards the front of the vehicle in this  case even if we're in four-wheel drive high or   four-wheel drive low back here there is no power  flow whoops let me get this block back up here   there is no power flow through see that's neutral  let's go to two-wheel drive or a four-wheel drive   high there is no power flow through the front  drive chain so the output shaft for two-wheel   drive will turn but notice the drive chain gear  does not turn and that will not turn until we take   another shift fork and move this shift sleeve  forward or to the rear of the vehicle sorry to   connect those two together now these gear teeth  here on the shift sleeve and gear teeth on the   front drive gear they have to be synchronized  the speed of those gears has to be synchronized   and so there's a special triple cone it's an  amazing synchronizer here and that the job of   a synchronizer and this this goes in between  these two is to make these two this hub and   this gear rotate at the same speed so that this  shift sleeve can just slide over because this is   called shift on the fly anytime you're driving  down the road in two-wheel drive you should be   able to hit a button or pull a gear lever and  shift into four-wheel-drive some vehicles have   a maximum speed limit of would still allow you to  do that if it's a push-button electronic control   transfer case but with without a synchronizer  you would not be able to shift in and out of four   wheel drive high on the fly now the four-wheel  drive low shift does not have a synchronizer   on most transfer cases and so to shift in and  out of four-wheel drive low back here you must   have the vehicle stopped and you have to put the  auto or your transmission automatic or manual in   neutral so that this shift can complete because  there's nothing to synchronize the speed of the   input shaft to the output shaft so you have to  be stopped so that they are synchronized when   you're stopped they're both gears are stopped  and so they're automatically synchronized but   to drive down the road this gear can this gear  that drives the front chain is stopped as you're   driving down the road in two-wheel drive so this  output shaft could be spinning 2,000 3,000 3,500   rpm this gear is stopped and so we need a really  good synchronizer to speed up this gear to match   the rotational speed of this output shaft now  if you think about it to turn this gear we also   have to turn this chain and the front output shaft  that front output shaft is connected to the front   drive shaft of your truck which connects to the  pinion gear which has to turn the ring gear so   it to turn this at all means that all of those  parts to rotate that's why it's important to   have the front differential oil be the proper  the proper oil you don't want to just throw   any old oil gear oil in that front differential  typically it calls for a synthetic gear lube and   the synthetic gear lube especially in cold weather  will not be as thick as in viscosity it'll be more   fluidic which will allow these gears to come up  to speed more quickly than if you had just your   traditional 85 W 90 weight gear oil in the front  differential so you've got to have the right oil   in the front differential in the first place  okay so to shift right now we're in two-wheel   drive for an output shaft gear drive chain drive  is not engaged to shift into four-wheel drive we   take the mode fork we move it to engage the drive  gear and now everything spins together and we're   in four-wheel drive once the transfer case is in  four-wheel drive then you can engage the front   differential into four-wheel drive a lot of front  differentials of disconnecting differentials they   have an electric motor with a shift fork that  disconnects typically the right hand axle shaft   from the differential side gear you can't shift  that in you can't actuate that front actuator   or front axle without having the transfer case in  four-wheel drive first and then of course to come   out of four-wheel drive you do the opposite you  well you take it out of four-wheel drive on the   transfer case and release the front axle so this  is a traditional four-wheel drive truck transfer   case this particular one is a Toyota but it could  just as easily be a BorgWarner or a new process a   magnum powertrain there's a lot of different ones  out there but if you take enough of them you'll   see that they all have a planetary gearset of  some sort to give you low range four-wheel drive   low they all have synchronizer a synchronizer  assembly of this one's a triple cone one some   of them are just double cone the more cones the  more synchronizing areas so the faster it will   synchronize to shift you into four-wheel-drive and  out of four-wheel-drive so we're out now we're in   on the fly as you drive down the road but the  problem with the traditional four-wheel drive   is that when you are in four-wheel drive on the  transfer case that locks the rear output shaft   and the rear propeller shaft and the rear tires  to turn the same speed as the drive chain and   the front output shaft and that if anyone of you  have driven a four-wheel drive vehicle and put it   in four-wheel drive on dry pavement you know that  you the powertrain binds and bucks and kicks and   it does that because you're trying to make all of  the tires turn the same speed when in fact they   cannot turn the same speed when you turn corners  the left and right tires turn different speeds and   the front and rear tires turn different speeds so  this brings us to the next style of transfer case   that this episode is about and that is the center  differential transfer case the center differential   transfer case has these same components it has  a planetary gearset a lot most of them do if it   has a four-wheel drive low range it still has a  mode fork and a mode sleeve and a drive chain to   engage and disengage the front differential  into or the front drive chain and the front   propeller shaft into a four-wheel drive locked  mode but there's also what's referred to as an   all-wheel drive mode so a transfer case that  has an all-wheel drive mode typically we'll   have one more planetary gearset right here in the  middle and so I'm going to show you that planetary   gearset style transfer case power flow next okay  we are now looking at the input shaft over here   and an output shaft from an open I'm sorry not an  open a center differential transfer case but they   sent our differential transfer case acts like an  open differential in a rear axle and anyone who's   ever messed with an open differential transfer  case if you lift a vehicle up on a hoist and   the vehicle is in park and you turn let's say  one of the rear wheels forward the other rear   wheel spins backwards and the reason for that is  the left and right hand axle shafts of the truck   or car spline to the side gears and since the ring  and pinion are stopped because the transmission is   in park and it stops the ring gear from turning  if you turn one side gear forward then through   the differential pinions that some people call  spider gears it forces the other side gear to   turn backwards so that's why a vehicle's tires  with an open differential of one spins forward   one spins backwards now if you have a limited slip  differential that won't happen typically unless   it's really worn out you'll spend one tire forward  or you'll try to spend one tire forward and won't   it won't spin because the other one wants to spin  forward also and it can't because you were in park   and it would try to drive the drive shaft at the  same time and it would not be able to well think   of a center differential transfer case as acting  just like an open differential it we've got the   power flow coming in think of this as the our  flow from the ring and pinion gear set and then   we have two outputs we have this output shaft that  goes straight to the rear axle and then through a   drive chain and gear we have another output that  goes to the front axle the front axle and the rear   axle are able to or propeller shafts drive shafts  are actually able to turn at different speeds due   to a special component I'm going to show you  here in this center differential transfer case   so let's take a look at the pieces involved here  so once again we've got our input shaft we've got   our output shaft here's our output shaft flange  this is off of like a Toyota four-runner this   was a vehicle that we had here I think it was a  2004 4runner but it said all will drive on the   door and so in just about any vehicle that's all  wheel drive is going to have some sort of a center   differential transfer case and center differential  transfer cases are different because they have   an additional planetary gearset so the additional  planetary gearset on this model is right here and   it's all enclosed in this housing unit you can't  see it very well you know well you can't see it at   all unless you unless you take it apart and on  this particular model it has been disassembled   so I want to show you show you the pieces here  there we go okay so we have a big open housing   here and inside of that big open housing and it  has some gear teeth here it has let me lift up   this little sleeve here get this gear out of the  way the equivalent of a ring gear from a planetary   gearset a thrust washer and then notice in this  carrier here we have what kind of look like planet gears of a planetary gearset but this is  actually a design based on the original Zexel   Torsen limited slip differential and what  we have here is the inner set of splines is   going to drive I believe the rear output shaft  and then the outer set of splines here ends up   connecting to the drive gear and chain and the  front drive shaft for drive shaft and so as this   thing rotates it operates on it of course has  a Sun gear down the middle here so we've got a   Sun here we've got planet gears we've got a ring  gear this is a planetary gear set but on a Torsen   style differential like this and they have these  in rear differentials they have these in front   differentials it's a high-performance differential  think of this is not only a planetary gear set but   it acts like a limited-slip planetary gear set  so a high-performance vehicle will typically   have a limited slip differential this will act  like a planetary gearset or an open differential   but if you force it to spend too much the this  the speeds of the rear output shaft versus the   front output shaft if the speed difference is  too much then these gears have binding actions   that force some of the gears down some of them up  into these thrusts Li thrust washers there's one   in the top here there's one in the bottom every  other one goes up one goes down and it basically   acts like a brake it slows down it doesn't do  a complete lock but it slows down and tries to   lock the two acts two output shafts together so  in other words as you're driving down the road   if the rear tires break loose if we did not have  this limited-slip style torsion style planetary   gearset in this transfer case the rear tires can  break loose on this center differential type of   transfer case and the front tires just sit there  and don't have any power put to them it's like   an open differential on a rear axle if one tire  loses power it sits there and dirt not loses power   if it if it loses traction it sits there spinning  while the tire that has all the traction doesn't   do anything and so we want to slow down the tire  that doesn't have traction and connect it to the   tire that does have traction that's what this does  except with the front and rear drive shafts so   if the rear axle lost traction and the rear tire  started spinning the front tire hat or front axle   has not lost traction this will slow the rear  drive shaft down and try to make it connect to   the front drive shaft which transfers power to  the front drive shaft which will help pull you   out of whatever situation you're in that's the  all-wheel drive setup now this is an older style solution to that problem the newer style  ones don't use the Torsen a limited-slip   feature in the transfer case they just happen  to an open differential transfer case so this   is just an additional planetary gearset and  then instead of using the limited slip action   in the transfer case to provide power to the  front differential they use the wheel brakes   the vehicles own brakes so the anti-lock brake  and traction control system on the vehicle now   is involved with the all-wheel drive stability  and traction control system if the rear tires   lose traction the brakes are pulsed momentarily  which slows down the rear propeller shaft or   driveshaft which forces torque to the front  drive shaft and causes the vehicle to move   forward we have left and right tires or the  left tire and the right tire that can spin   at different speeds let's say the right rear  tire lost traction and the left rear tire did   not we can pulse the brakes on the right rear  tire slow it down and force the torque and the   power to go to the left tire that still has  traction and get you out of that situation so   the new systems with vehicle stability control  and all-wheel drive with an open differential   transfer case or a center differential transfer  case it's basically the same thing they're open   it's a center differential between the front and  rear axles but it acts like an open differential   we use the brake system to apply or bias torque  to the front or the rear differentials okay so   this assembly is on or it's in this output  shaft and so I have another one here that I'm going to insert so here is our input  shaft output shaft and then here is an   assembled the limited-slip Zexel Torsen style  planetary gearset like I just showed you this   is going to go right here on the input shaft and  output shaft at the same time so let me get that   set up we've got an additional hub that's  going to connect in here to send power to   the front wheels so our output shaft is going  to connect right into this piece there we go okay so center differential transfer case we've  got the input shaft we've got the output shaft   notice still there is no direct connection  input shaft to output shaft so let me put   the output shaft flange on here I can turn the  input shaft over here there's no power to the   output shaft so we still have a traditional  planetary gearset here's the Sun gear here's   the planet carriers the ring gear is up in the  back of the transfer case housing and there is   a sleeve a shift sleeve here it is to connect  the input shaft to the output shaft just like   on the traditional transfer case power flow  that we looked at already and so let me get   this one connected here it's got to have spline  teeth against spline teeth so this is going to go   on or taper teeth against tapered teeth these  sleeves can be put on backwards quite easily   in a lot of cases if they're if they don't  have blind splines this one this one does oops now let me get this one lined up first  there we go of course it falls on as soon   as the other piece falls off so this sleeve  here is going to connect the input shaft to   the output shaft except notice that it's what  I guess I've stated that wrong this sleeve is   going to connect the input shaft to the center  differential now the center differential has   like any differential with a left and right side  bearing one of those equivalent side bearings is   the rear output shaft the other one through this  hub right here is the front output shaft so if I   engage the input shaft to the center differential  and I start to turn it as long as there's equal   resistance on both the rear and the front drive  shafts they will turn this these two pieces will   turn the same speed but if the front loses power  or loses traction and starts to spin and then the   rear ends up stopping notice the front output  shaft here can spin real quickly or if the rear   lost traction and the front did not let me hold  this one then it can spin freely so these are   just like the left and right axles and to let me  illustrate that a little bit better with another shifts leave and the and the rear output  shaft tapered teeth they're both tapered teeth okay and I get this bearing up in here alright so here is our front output and there's  a shift sleeve here that can connect it to the   center differential so it can spin independently  oh and by the way notice here if I spin the front   output shaft one direction notice the rear  output shaft spins the opposite direction   that's just like an open differential same  thing if I spend the other one they always   spent opposite directions of each other so we  have this shift sleeve on a hub that when it's   back like this that's the all-wheel drive mode  and it allows for a difference in speed between   the front drive shaft this is where the drive  chain connects and goes to the front drive shaft   and front axle here's obviously where a rear  drive shaft connects and goes to the rear axle   in on a center differential transfer case these  gears or this center differential planetary set   allows for the front and rear wheels to turn  different speeds that way even though you're   in all-wheel drive where you have power to all  four wheels you can turn corners and the vehicle   will not buck and kick and surge as you're like  a typical four-wheel-drive vehicle would because   you were trying to force the tires to turn  all the same speed this allows them to turn   at different speeds but this transfer case also  has a four wheel drive high selection so if we   take this shift sleeve and we lock it to the  center differential outer housing by moving it   back like this we have now forced or we've now  bypassed that center differential and now whoops   all of these have to be connected together right  there and now everything spins the same speed in   the same direction and now this acts just like  that other transfer case I showed you at the   start of this video we're in four-wheel drive the  front and the rear propeller shafts drive shafts   turn the same speed and direction and you'll get  the bucking and kicking and four-wheel drive on   dry pavement which you should never drive  a four-wheel drive on dry pavement alright   we also have this other sleeve back here along  with this planetary gearset that comes on here   that gives us the four-wheel drive low position  some will have a neutral position it still has   all three positions it'll have low if the shift  sleeve is back all the way neutral in the middle   and four-wheel drive high and two will drive  high or just two will drive what nobody calls   a tool drive high when it's forward like this  but we've already gone through plant the gear   reduction operation in the first demonstration  I did in this video so we won't do it here but I   wanted to point out the big difference between  an a center differential transfer case and a   traditional transfer case is an additional  planetary gearset so we've got this planetary   gear set that gives us four-wheel drive low  four-wheel drive high and two-wheel drive   we have an additional planetary gearset in the  middle that allows the front and rear tires to   turn at our front and rear drive shafts to turn  at different speeds and then you have another   open differential in the front axle in the rear  axle that allows the left and right tires to turn   at different speeds so a vehicle that has one  of these actually has three open differentials   in it so this has been a demonstration in  description of the difference between a   traditional four wheel drive transfer case and a  center differential transfer case have a good day

Channel: WeberAuto

Views: 167,471

Keywords: Dodge, GMC, CCAR, Professor, Transfer Case, GM, center differential, Ram, John Kelly, Chevrolet, Offroad, Ram Pickup (Automobile Model), 4WD, Aisin, Chrysler, CAT, Differential, Ford, Toyota, 4x4, Guy in wheelchair, Ram Trucks (Brand), All wheel drive, NATEF, NACAT, ASE, Mud, Pickup Truck (Automotive Class), STEM, AWD, Weber State University (College/University)

Id: ESm0PPBkAQQ

Length: 41min 43sec (2503 seconds)

Published: Tue Mar 17 2015