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Alright, guys, I want to show you how a torque  converter works and show you the different   pieces of the torque converter, and I believe it  will help you make sense of some of the pieces   of the transmission, and then of course, how the  power from the engine actually comes into the   transmission, and into the transmission input shaft. as  you know with an automatic transmission   vehicle we don't have a clutch pedal or  clutch disc like the previous class that we   just finished but somehow we've got to be  able to still connect the engine power to   the input shaft of the transmission so that is  done with the torque converter there have been   several design changes of the torque converter  over the years but overall the basic design the   basic theory of operation has not changed very  much since the very first ones in the late 20s   and so the probably the best way I've been  able to show students how a torque converter   works is to use a fan. so I've got an electric  fan right here and this fan is going   to when I turn it on it's going to represent  the engine's crankshaft and the fan portion of it inside of the torque converter, there's a piece  right here that is the equivalent of that fan   and it's called the converter pump, not to be  confused with the oil pump of the transmission,   so this is the converter pump and it is welded  directly to the housing of the torque converter   and then we've got these big lugs that it bolts  to the flexplate and the flex plate is   bolted to the engine's crankshaft, so if the engine crankshaft  turns at all, so does this fan. so this fan represents   the speed of the engine. and then down inside the  torque converter not physically connected to this   fan is a different fan, right here that's called  the turbine, and the turbine is what connects   directly to the input shaft of the transmission  so if we can make the turbine spin then we've   got power flow coming into the transmission.  well the trick is this first fan the converter   pump that we've talked about or introduced to  you since right here underneath as far as   this demonstration is concerned, and it's going to be  basically blowing fluid on the other fan to make   it, to try to make it rotate, so that is  what's called a fluid coupling but I want to show   you a few things about the fluid coupling before  we get too far into the other pieces here so so   this fan represents the engine if I turn this fan  to the lowest lowest speed, I've got a painted the   back with fan blades black, and I've got a photo  tachometer here, that there's a little piece of   reflective tape I put on the fan, and on low speed  I can take this photo tachometer and point it at   the fan blade and get the speed of the fan  off of that one reflector, and it is turning at   670 rpm approximately, so the engine is turning at  670 rpm. so now I'm going to take another fan but   this time this fan represents the turbine this  fan represents the turbine that connects to the   input shaft of our transmission and remember  the fan from the engine which is the   converter pump has to blow fluid on the fan  for the turbine. Now I've got this plugged in but   it doesn't it's I'm not going to turn it on at all  so if this fan moves at all it's because of the   four which represents the fluid flow inside the  torque converter, so I'm going to put the two fans   together, so I've got the engine fan turning I  have no physical connection between the engine   fan and the turbine fan and if I come in with  the photo tachometer here remember we had 670   rpm approximately over here, I've got 408 rpm  on the other fan. let me turn that    off for a minute, if we have 670 rpm on the  engine fan but only 408 rpm. on the input   side we've got some inefficiencies here we've  got some loss of engine power engine torque and   that is going to decrease fuel economy. well  prior to about 1978 that's how the   majority of torque converters worked, there was  there was no way to physically connect those   two fans together they were allowed  to slip and as you drove down the road in your automatic    transmission vehicle all that slipping would  cause what is known as fluid friction. and any   type of friction even rubbing your hands together  creates heat, and so the torque converter is the   number one heat generator in a transmission, and  it generates the most heat whenever there's a   huge difference, whenever there's a difference,  between the speed of these two fans so if we   can hook them together then there's basically no  heat generation or very little heat generation   but if we allow them to slip then there's a lot  of heat generation now who's ever who of you has   ever sat at a stoplight or stop sign and got one  foot on the brake and you decode, hey, I'm going to race   this guy next to me, so then you get the engine  full throttle but you still got your foot on the   brake so with your transmission in gear that stops  this fan from rotating because if this fan rotates   the vehicle is going to move so one fan is vehicle  speed-sensitive the other one is engine-speed   sensitive but now you've revved your engine way up  and your engine can only rev up to a certain point,   you ever noticed that it only revs up to this or  near that 1500 maybe 2500 rpm depending on the   vehicle but if you put it in neutral revs up a lot  higher that's called the stall speed of a torquing   group because the engine trying to push the fluid  through all of these veins physically doesn't have   enough power to rev any higher because of all this  resistance the fluid friction so that's called the   stall speed. the stall speed there's an actual  specification for stall speed for almost every   vehicle every transmission it's a test you can  do to see if it's working correctly and there's   other internal pieces of the torque converter that  we need to talk about that can affect that stall   speed, but anyway, think about that if the turbine  turbine fan is stopped and your engine fan is   spinning at 2,000 rpm at that point you're going  to create the most heat, and if you've ever read   service information about a stall test or let's  say you're trying to diagnose an engine misfire   and you decide well let me just load the engine  here in the stall by one foot on the brake one   foot on the gas almost all service information  tells you not to do that any longer than about   10 to 15 seconds because as it turns out I heard  one specification that the temperature increase   in the torque converter at maximum stall like that  increases 10 degrees Fahrenheit per second so 15   seconds you've got 150 degree rise in temperature.  yeah, okay, I'm sorry, I'm really struggling with this idea   if fluids are touching, how are you generating heat for fluid  that's designed to keep things cool anyway? The   fluid has to physically move through all of these  veins and rotate back and forth fluid doesn't   just flow freely every time it has to make a turn  there's fluid friction fluid has little molecules   in it and every one of those have to take a turn  so those molecules rub on each other and creates   heat, especially under higher pressures and high  speeds, okay so it's really bad to overheat your   torque converter now yesterday I mentioned to  you that when that all the fluid that leaves the   torque converter immediately goes out to the  cooler out there in the radiator or in front   of the radiator to help cool it down and then it  comes back in where? where does the lube,   Oh, I just told you, where does the cooler fluid  go after it comes back in from the cooler? it   doesn't just drop into the pan and it goes to  lubricate all bearings bushings and and gears   then it drops into pan. alright so normal  operating temperatures of automatic transmissions   are between say 180 degrees Fahrenheit this is  flow temperature and about 260 turns 270 degrees   and the fluids that are made for automatic  transmissions are we made to withstand that   type of temperature and so if we overheat the  torque converter some damage can occur even   to the flu even though the latest fluids they  have a maximum temperature would still start   to break down, they won't break down until you  reach this temperature, the fluids have   to be a lubricant, they have to be a hydraulic  they have to act as the hydraulic, we can't have   rusty parts, we can't have it freezing.  We are asking a lot from fluids. Well if you took a   transmission that was already warmed up let's say  it's a 250 degrees and now you keep holding your   foot on the brake and the gas at the same time the  fluid in the torque converter now can easily go   over 300 degrees which ruins the fluid, it doesn't  necessarily ruin the transmission instantly, it can   if you keep doing it too long and you  don't give it enough cooldown time in between most   service information tells you to wait a couple of  minutes to allow the fluid to circulate through   the cooler to cool down, by the way, the most  vehicles the cooler is in the radiator so what's   the temperature of the fluid in your radiator  thermostat it opens a 195 on most vehicles so   if that's cold too transmission fluid. think about  a transmission fluid is cooled in 195 degree water,   coolant. transmission is run hotter than engine  coolant, which some of the cooling fans on passenger   cars don't come on until 230 degrees. The  cooler in the radiator can also be a warmer or   a heater for that fluid in the wintertime so to  warm help warm the transmission up the the heat   can transfer from the warmer engine coolant  into the transmission and then the   other way around it gets too hot but anyway so  you're sitting at a stop sign put on the brake   put on the gas creates a lot of heat it's very  bad for the torque converter if you've ever seen   a torque converter that the metal has physically  turned blue that doesn't happen till until around   700 degrees. what I've, really, yeah so it's really  been abused. yeah what would cause what's besides   holding your foot on it and keeping the engine  loaded, what is the usual cause of overheating the torque   converter, is it too much weight on the vehicle? okay  yeah and I'm just coming to that so under what   other situations besides sitting there through  one foot on the brake and one foot on the gas   could this happen? say again - towing a really big boat  or anything really heavy, okay so if   you notice that most trucks have a button on the  end of this automatic transmission shifter called   Tow/Hall? the Tow/Hall button depending on which  transmission it is, is going to prevent you from   going into overdrive on most transmissions or  double overdrive whatever it may be and it'll help   keep the transmission in the range to where it's  not loading the torque converter as much as as it   would normally so what I'm saying is it, well look  let's take a different example and then you   can relate that to towing, let's say you're just  driving down the freeway an empty pickup truck or   passenger car, it doesn't matter they all have torque  converters of similar components and   design. you're in overdrive, you're cruising  down the freeway and there's let's say there's a   truck or somebody going slow and you have to slow  down slower than you were driving or slower than   the speed limit and then you're stuck behind but  then suddenly there's an opening and you can pass   that when you go to pass them obviously you're  not going to stick your foot on the brake pedal   you're going to mash the accelerator pedal clear down to  the floor, aren't you? when you put the accelerator   pedal clear to the floor the transmission is going  to downshift and when the transmission downshifts, that   will allow the engine speed to go higher which  develops more torque which is to help you accelerate around   this vehicle or whatever it is you're trying to pass.  but when that happens vehicle speed didn't change   let's say you're doing 60 miles an hour suddenly  you stomp foot to the floor, you're still   doing 60 miles an hour, the only thing that changed  is your engine rpm went way up, well remember this   fan is vehicle-speed-sensitive so it's still  doing whatever speed it was to get you going   60 miles an hour, all of a sudden the engine rpm  goes way up so this other fan suddenly goes up   to pretty much the stall speed of the torque  converter, so if you could have a 2,000 rpm   difference driving down the freeway between  the speeds of the two fans in   the torque converter, just from passing something,  well that's that's passing someone, but now let's   imagine that you're towing a trailer and you've  got your foot down on the throttle more than you   normally would with an unloaded vehicle because  you're hauling however much weight and especially   if you're hauling too much weight you're going  to have to compensate to that extra weight by   stepping farther down on the accelerator pedal  so if you step farther down on the accelerator   pedal it tends to kick you down to a lower gear  but it doesn't increase your vehicle speed it   only increases engine speed which takes you to  that stall speed again except this time it's not   just while you're passing it's the entire time  you're towing the vehicle, and especially going   up a hill, so the tow-haul mode attempts to try to  prevent those situations and on some transmissions   it actually watches fluid temperature and if  the fluid temperature starts to rise too much   it's going to lock those two fans together with  a part called a torque converter watch and I'll   show you the torque converter clutch here in just  a minute but we now have the ability and have   since the mid-70s to hook these two fans together  under certain situations with a torque converter   clutch there's been various designs of that over  the years but the majority of them it locks them   straight together, the Alison's that were working  on here it locks them together does not allow for   any snow the later model the torque converters  do allow for a little bit of slip because of   OBD2 regulations that came out in 1996 we have  to monitor engine misfire by monitoring the   rotational speed fluctuations of the crankshaft  well if your per converter clutch is engaged there   were situations where you'd get a fault PO300  engine misfire code because you would accelerate   or decelerate with the torque converter clutch  engaged it's like driving a manual transmission   and being in too high of a gear, and you give it gas  or let off the gas the whole vehicle just kind   of jerks, an automatic transmission does a similar  thing when the torque converter clutch is engaged   and it would actually out the crankshaft  position sensors into thinking that there was   a engine misfire so their cure for that was  to change the torque converter to where instead   of being torque converter clutch, to instead of being  totally locked up it would allow for a certain   limited amount of slip somewhere around 45 rpm  is pretty typical of what I've seen so enough   with the electric fan demonstrations let me show  you the actual pieces of the torque converter and   how they relate to the transmission. all  right let's start with just the basic torque   converter housing like you guys have got out  of your transmission, just a reminder of what we   talked about the other day these these flat spots  on the torque converter matched the flat spots of   the oil pump drive gear, and so anytime this entire  housing terms it's going to turn the oil pump so   the oil pump housing actually has the front seal  that keeps fluid from leaking out it has a bushing   in here that can't be any more than a maximum  diameter which is a specification for that there's   a minimum diameter for this area here and if  that's excessive it doesn't matter how good this   seal is it's going to leak anyway because the seal  can't hold any structural support but you've every   taking the torque converter out and tried to put  it back in it's quite a trick to get everything   lined up and get it all in typically there are  three things that have to line up and I want to   show you what all three of those things are one of  them is the flats of this oil sometimes it's not   flat sometimes it'll be grooves cutting that this  housing here will be the launches that fit right   in the grooves but this has to line up so there's  one of the three clicks as as you try to put the   torque converter back in the vehicle to ask the  other two there's a there's a part called a stator   support and if you look at your oil pump body the  stator support is sitting in your oil pump body   and they, Allison calls it a ground sleeve, and I  don't want you to remove it the instructions in   our manual tell you how to remove it but don't  remove I removed it just to show you what it   looks like, but this is pressed into this housing  in this housing is bolted into the transmission   this does not spin this stator support shaft  does not rotate it just sits there solid and so   it has some splines on it that go down in and it  has this point with a part called the stator this   is the stator support it supports the stator we'll  talk about stator here in just a minute but that's   the second set of splines that has to line up  and then of course your input shaft right here is   the third set of splines that has to come in and  line up with that turbine thing, so one two three   sets of things that have to all line up as you  put in, well let's take a look at the parts   in the torque converter that connect to these. talk about  their function, so we've already talked about the   converter pump that's the fan that turns  with turns engine speed and we've already talked   about the turbine and it's the one that splines to  the input shaft and that's the one that turns if   the vehicle moves and if your transmission is  in gear this totates, the vehicle will move if   you're in neutral this can rotate and the vehicle won't move  that's the stator, I'm sorry the turbine, there's   the turbine, on the back of the turbine is a set  of splines and I told you that in the mid-70s   they started using a torque converter clutch,  well there the torque converter clutch is this   big piece and it sort of looks like a clutch disc  in a way we've got the rotational damping Springs   we've got fiber material here it looks like  a giant clutch disc but it has spline teeth   right here that are going to hook to these splined  teeth of the turbine and so we set that over here so it sits there, and it turns with the turbine  and then that surface air that flat surface   area there, and somebody has moved my sticker,  that flat surface has to sit against what's   called the converter cover this part obviously  is what bolts to the flywheel the hooks to the   engine rotates with the engine but notice there's  a nice flat surface right here a nice flat surface   is for this clutch disc material to be pressed  up against and when you press this clutch disc   up against this converter cover it physically  connects the turbine which was one of the two   fans that we talked about to this housing that  is welded to the converter pump which is they   the other fan the engine speed fan and so the torque  converter clutch is the part that hooks the two   pieces together but it does it by, the way  it's shown here, oriented here, when it's down   like it is the converted clutch is released this  fiber material does not contact this flat surface   right here but when we want to apply the torque  converter clutch we run a fluid pressure on the   backside of this and it physically lifts it up so  this can go up and down this way when it comes up   it pushes solid against this flat machine surface  here and locks the turbine the whole turbine   assembly to this housing and since once again  since this housing is welded to this housing which   engine speed-driven fan the converter pump  that locks the two together and when they're   locked together there is no heat generation and  it'll stop heat generation and it improves   fuel economy because now we don't have that  difference in speed remember either one fan   had what 670 rpm the other one is 408 so roughly  at 262 rpm difference between the speed of the two   fans this would reduce that to zero, now the word  of warning to you the bolts that go into these   lugs have to be the correct bolts if you lose one  of the bolts down the drain or whatever you can't   just go grab any little bolt and stick in there  well you can but you shouldn't just grab any old   bolt and stick in there there's two problems  with putting the incorrect bolts in there one   is it might be a different weight physical weight  than the other bolts which could cause a vibration   because this part rotates it at engine speed  the second one is what if it's too long if it's   too long it will thread clearing to the bottom  you'll keep cranking on it and it will make a   dent somewhere in this flat machine surface and if  it makes a dent in this flat machine surface it's   going to tear this clutch material off the torque  converter clutch disc and then you'll end up with   the torque converter clutch that won't apply and  it will trigger all kinds of trouble codes that   will lead you to diagnose that you need a totally  new torque converter and all of this material now has been   run through the system now it's out partially  clogging the oil cooler transmission oil cooler   another reason to flush the cooler and then so  we can apply and release this we apply and release   it through there's a hole right here in the end of  this input shaft this turbine shaft and so if we   send fluid up the center of that hole it comes up  in front here and pushes away pushes down on this   pressure plate as we look clutch disc as we're  looking at and then it flows through comes back   out another hole and goes out to the cooler  if all we do is reverse that flow which is the   job of one of these valves in this oil pump body  then the fluid wants to come into the hole here   so any fluid that was in this area now goes  down the center of the input shaft we build up   pressure on the back side this clutch material  acts like a big seal and it prevents any fluid   from leaking through, so there's about there  that just simply reverses fluid flow to apply and   release the torque converter clutch. now there's  one additional part have not talked about here in   the in the torque converter so let's get to  it and it's one of the most important ones it it's what makes the difference  between what used to be called a   fluid coupling and what now the addition  of this part is called a torque converter this piece right here is called the stator and  the stator goes in between the two fans so think   of this as a piece that fits in between those two  fans the stator has a set of splines on the inside   of it that is supported by of course the stator  support and that stator support doesn't rotate   it just sits there but those splines versus  the stator blades here have what's called a   one-way clutch inside which means it will rotate  one direction only but not the other direction   that's a one-way clutch so rotate this way but  not back the other and the purpose of this piece   is to multiply engine torque this is the big  difference that you'll get in power between the   vehicle with an automatic transmission and one  with a manual transmission I've told you that   you had two equally equipped vehicles same gear  ratio the same engine same everything except one   was automatic transmission and one was a stick  shift the automatic without accelerated and now   pull it power-wise as long as you could keep it  cool it's because of this piece right here and   stators can multiply engine torque anywhere from  about the lowest stator multiplication factor   I've seen is about 1.2 the highest I've  seen is is 3 so whatever engine torque is   You multiply it by that number and that's  what's delivered to the input shaft of the   transmission, but only under certain conditions and it  just happens to be those same conditions that   overheat the torque converter under high load  maximum stall which is when you need the extra   torque anyway yeah so really at 765 was that thousands  we'd have to look it up it's probably 1.2 1.3 yeah   that's what's coming into the transmission and  then you've got additional torque multiplication through the gear sets, okay so let's talk  for a minute about how what how the turbine works   or not the turbine stator what's what so what's  so magic about this thing that it can multiply   torque well if we go back to the two electric  fan example we've got the one fan which is the   converter pump blowing fluid onto the other fan  which is the turbine, well the fluid if you   look at those two fans unlike those fans it  doesn't just blow through the fan go away it's   going to come in towards the center that has  to make a u-turn and come back out I'm sorry   it goes the other way it comes in here makes  a u-turn comes back out on the inside so it's   making this constant loop between the converter  pump fins and these fins so that as this rotates   a centripetal force is going to have the fluid  come to the outer edge and work its way back   towards this one but as the fluid hits it, it's  going to cause this one to rotate and then the   fluid makes a u-turn and comes out the middle  right here, waiting right there in the middle   for that fluid to come out, is the stator and the  stator is going to take that fluid and make it   pretty much make a 90-degree angle and turn and  take that and keep in mind this is pressurized   fluid it's moving rapidly and it's under high  pressure 60 psi or so it's going to actually end   up redirecting fluid instead of coming straight  across from the turbine it brings it on an angle   and the angle ends up hitting these fins in the  direction let's see it would be this way in the   direction that's already spinning, so imagine this  was spinning with the engine crankshaft but now we   take some high pressurized fluid and we blow it  all these fins in the direction that's already   spinning what's it going to do? it spins faster it  spins easier it just imagine taking one of those   electric fans with an air nozzle turn the fan on  it'll spin one speed but now you hit an air nozzle   with the right angle to it the fan would speed  up that's what's happening here, it's not is it   called self-energizing, making something, no, no it but  this only occurs when there's a huge difference   when there's a difference in speed between these  two fan so heavy acceleration going up a hill   stuff like that under the same conditions where  it would overheat also so it's not a permanent   always you have more torque more power it's only  pretty much what you need and then the rest of the   time once these two fans pretty much catch up  to the same speed then it the fluid that hits   this ends up hitting it on a different angle and  then the roller clutch in there just allows it   to spin freely with the two fans the turbine  and the turbine and the converter pump anyway.   so one more time, we've got two fans we've got  a stator in between the stator whenever there's   a difference in the two speeds of these we'll  lock up on that standard support redirect fluid   to blow fluid on this on these blades all at  the same time multiple nozzles all at the same   time helping this rotate in the direction that it  already rotates so a fluid coupling is basically   a torque converter without a stator, that's kind of  a gutless dog, and it didn't work out very well, it   worked but it just didn't have the acceleration  that you would get once they came out with just   the stator and I've seen some torque converters  that have two stators and multiple   pieces, they are ones that end up multiplying  the torque clear up to three is the multiple   so a torque converter and you'll need to know this  for the ASE exam torque converter does four things   we talked about all on what let's review  the first thing it's working better does is it   drives the oil pump of the automatic transmission  with those flat spots or notches on the front of   then the second thing is the two fans we talked  about it provides a fluid coupling the third thing   is we've got a torque converter clutch that can  engage to improve fuel economy and reduce heat   buildup inside the torque converter and probably  most of one of the most important things after a   fluid coupling because the fluid coupling replaces  the clutch disk a manual transmission the second   most important thing is the stator that multiplies  engine torque which is the huge advantage of one   of the huge advantages of automatic transmission  all right well any questions concerns, yeah,   when clutches engaged it was under what conditions  of the converter? The clutch will engage under   low load the converter clutch percolator clutch  will engage under low load conditions pretty   much flat driving not going up a hill it'll stay  engaged going down it.    the only other time I've seen them  come on is if the transmission control module   the TCM that controls the transition detects  that the transmission is overheating it'll go   into an overheating mode where it will lockup the  torque converter clutch now these torque converter   clutch normally don't engage until you're in  overdrive but sometimes they can engage as low   at second gear just depending on the vehicle year  make model and so on but if you're overheating it   can keep this thing on clear down through  second gear never do we want it in on and   first because if you pull through a stop sign  and the converter clutch is engaged that's like   driving a manual transmission pull it up to a  stop sign and not step around the clutch the   clutch pedal will kill the engine. Alright that is torque converters