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 fake 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
I applaud his patience. The physics processing centers in my brain were screaming "You should have paid more attention in science class" every time she asked a question like "How does a fluid that's designed to keep everything cool heat up?" Or when she asked about the stator: 'Is it called self energizing, it is making itself do it, or no" almost referring to it being a free energy device. I almost snorted. Then I remembered that she is genuinely trying to understand this and that it's good that he is being patient with her and trying to explain this. It just bothers me that these are most likely college students, and at least one of them doesn't seem to grasp the basics of physics and friction.