Basic auto trans valve bodies

in part six of this seven part basic automatic transmission series i'm going to talk about valve bodies consider the valve body the traffic cop of the transmission it's controlling the pressures in the transmission it's controlling the direction of fluid flow it's obviously a very important part and it works close with the electronics in the transmission solenoids sometimes will control valves in the valve body either to control direction of fluid flow and pressure and in modern transmissions they put so much more emphasis on the electronics that the valve bodies themselves have actually become a little simpler by comparison a modern transmission has less valves than a old-school transmission that didn't have any electronic control and the old school transmissions they had to have a valve to address every little issue every little shift concern that you've got so nowadays they can let the solenoids into computer control they can adjust so many things and adapt to so many things that they've made the valve body the valve side of it simpler and then just enhanced the electronic side the computer control side on this slide i'm showing you pretty much the evolution that's occurred and this is using a honda as an example if we look way over here the honda 5 speed it's got this is the hydraulic schematic and along the edges of the the schematic here we see the electronics there's only six solenoids being shown up here and along the top there's the the hydraulic clutches that they've got and then the torque converters way over there we're going to get into the hydraulic schematics and all that kind of stuff later specifically with different types of units but what i'm trying to show you here is look how complicated that hydraulic schematic is for a five-speed transmission now we look that was 2008 so 12 years ago and then now we're looking here at this 2014 six years ago this is a six speed so they've added one gear to it and you can see all right we still got some solenoids we got solenoid control going on there we got more clutches but the hydraulic schematic actually got simpler so they move some of the responsibility for the valving over to the solenoids and to the electronic side and then this example here is a 10 speed you can see they got tons of solenoids all these little kind of canisters that they've got in the middle those are different solenoids and they've got very few valves they don't have near as many valves on this 10-speed transmission as they did on this five-speed and they got you know the hydraulic schematic just by looking at it you could tell it's a lot simpler even though the transmission is way more complex so this just goes to show you that over the years they've moved the responsibilities over to the electronic side of things to the computer control side of things and kind of relieve some of those duties from the valves that doesn't mean that we still don't have valves and valve body obviously we do we got different valves like shuttle valves shift valves and we got pressure regulator valves we still have to understand how those things work and how they operate and that's where we're going to go to next when we get on the bench every automatic transmission is going to have a veil body of some sort and some of them are more complicated than others the older transmissions like back in the 70s and 80s those actually had more complicated valve bodies than these modern transmissions do and part of the reason why is because modern transmissions they rely so heavily on electronics you know we've got a lot of solenoids in fact this one's got a computer built into it right there that part so the operation of the hydraulics have actually become a little simpler over the years in regards to valve body operation a lot of it has been moved over to the computer side and solenoids in most valve bodies you're going to find a few different types of valves and i used to be able to say that all transmissions are going to have these three types of valves one being a manual valve it's a physical valve that is connected to your shifter that allows you to either operate and drive or reverse there is that's one of the valves that actually doesn't need to exist anymore some transmissions that are produced now don't even have a manual valve they do everything electronically they have a solenoid that engages park and releases park but they don't actually physically have a valve that moves that's connected to your shift linkage and part of that's because of the start stop technology that they have on vehicles and also just the electronic operation the kind of movement towards everything becoming electronic controlled but there are a couple other valves that are found in automatic transmissions that are pretty much found throughout one of them is a switch valve and switch valves are valves that allow you to control pressure in one direction or the other they don't regulate pressure they just direct pressure and the other one as you may figure out is a pressure regulator type valve those are the valves that allow you to control how much pressure is in the transmission or in a fluid circuit and there are a variety of different types of pressure regulators out there too there are ones that just regulate it to a constant pressure all the time and we'll see an example of that and then there are also pressure regulator valves that allow you to vary the pressure depending on the demands and the conditions of how the transmission is being operated another thing that's pretty common with the hydraulic side of things and it's often incorporated with the valve body are accumulators a lot of transmissions nowadays don't even have accumulators but many of them still do so it's worth covering and incorporated in these valve bodies are solenoids solenoids that are going to control the pressures they're going to control the direction of fluid as needed and we'll cover those along with the valve body discussion before i get too far into it i want to mention that most of these that i'm showing here these are cutaways these are valve bodies that have had the surface cut off of it so we can see the valves a little bit better when you take apart a normal valve body like this one here you don't get to see the valves like you get to see in these cutaways they are basically going to be these worm tracks these channels the valves are going to live in these bores and these passages on the inside so in order to access them you're going to have to pull these plugs out on the end and then pull the valves out that's something that if you do that you're going to want to pay close attention to the position of these valves and the location of the springs and keep things like the springs in their proper order don't mix and match them because these springs are calibrated and if you get them in the wrong spot the transmission is not likely going to work properly that's why it's a good idea to have something to help organize the valves and like this little valve body tray here as you pull these valves out you can lay the valves in these little grooves here with the everything in order with the end plug the spring the valve and you can even clean them off on these little trays which is nice so if you ever take a valve body apart make sure you keep things in order don't assume that you're going to remember where they go and also don't assume that just because you've got service information that the service information is going to be good enough for you to be able to put a valve body together with a pile of springs here and a pile of valves there that would be a maybe a rude awakening if the time came and you're like okay i'm putting this thing back together and these springs here they look the same but they feel a little different or this spring and that spring these springs are interchangeable they can go in the same spot you can see this one's got different thickness coils and then this one it's got a color for identification so if you didn't pay good close attention to it you might find a mess that you're gonna get into and trust me i've had students do that not knowing i walk over and they got all the valves out and they got a pile of springs over in the corner and i'm like how do you think you're gonna be able to figure out where they go and they just assumed that the service manual would have that information luckily enough i usually have enough transmissions here where we can take one off and lay them side by side and figure it out but not everybody's got that luxury let's start this by looking at a simple valve body that doesn't have that much going on this is a cutaway of a 4l80 valve body there's like i said there is not a whole lot going on on this valve body so i it is cut away so we can see the passages from the top this right here is a manual valve and like i mentioned before not all transmissions have this but the vast majority that are out there still do this is the valve that's physically hooked up through linkage into the cabin of the vehicle so that the driver has the ability of shifting between park reverse neutral drive all that kind of stuff and like i also mentioned that some of these are now gone because we just let solenoids control pressure to the clutches as needed and they might have electronic motor to engage park physically you know the the lock park but they've eliminated this valve and then we also have like these are different solenoids and i'm missing one that goes here but this these two solenoids are shift solenoids and this is a pressure regulator solenoid and the solenoid that normally lives here would be for torque converter clutch operation the solenoid directly works on the end of that valve so just kind of imagine the pressure through the solenoid through the torque of vertical solenoid would work on the end of that valve right there these three valves right here are shift valves this is a one two shift valve two three shift valve and three four shift valve a shift valve is going to control the direction of pressure and these shift valves right here are controlled by these solenoids so when the solenoid energizes it traps pressure behind the shift valve and the shift valve is going to shuttle over like that and when this solenoid energizes it traps pressure behind this side of the shift valve shuttles it over so on this transmission in first gear solenoid a there's two solenoids a and b a is on b is off second gear both of them are off third gear b turns on a is still off and in fourth gear they're both on so when you shift first second third and fourth you're changing the you're changing the state of these solenoids and you're changing the position of these valves and like i said these are shift valves also sometimes would be called shuttle valves because they don't control the amount of pressure but they control the direction of pressure and the way they do that is if you imagine like when i'm in first gear this solenoid would be turned on and the position of this valve would be in that position as shown right now the line pressure is going to be present on this passage where the tip my finger is you might see that little dot on that valve on the valve body i drew that there well the pressure can't go anywhere at this point it's kind of stuck it's bumping right up against us but when i shift from first to second and i turn the a solenoid off allows the spring to push the valve over now you look see what happens is the passageway is now opened up and guess what this does this feeds our second clutch circuit and when we shift this transmission from second to third fluid pressure is going to be line pressure present in this passage right here this is the passageway that goes to the third clutch so when we energize the solenoid you can see that's going to move that valve over and now i allowed a little bit of tension on that spring now i allow fluid pressure to travel from this passage to that passage and it's going to feed our direct clutch circuit our third clutch circuit now when i shift to fourth gear this cell is going to turn back on and not to confuse you or anything but this is still going to be kind of locked into this position because fluid pressure will be back here from when it when it up shifted but they're going to use this solenoid to control this shift valve and fourth pressure which is or the line pressure is going to be present right here where this little dot is in this passage and then when they energize the solenoid a and they shuttle it you're going to now expose pressure to the fourth passage circuit overdrive right there so this would be third that would be fourth and now full of pressure was able to go from here to there so we've got first second third and then this would still be in this position but i can't do it with only one hand and then fourth these are shift fails they don't regulate pressure they just control the direction of pressure on this slide this is showing the hydraulic schematic showing a shift valve in one of two positions on the top here we could see this is the solenoid on with the solenoid on the passageway for fluid to find its way out through the solenoid is blocked off and then fluid pressure can build up on the side of the shift valve and push that shift valve over to the left as it's drawn and that's going to compress the spring on the end on the bottom image you can see the shift solenoid is turned off and the fluid that gets tries to get behind that shift solenoid can exhaust out there's still little arrows there it's able to exhaust out so that means there's really no pressure building up on the back side of this valve on the right side of this valve so the spring can then shuttle the valve over to the right so when we look at the shift valve at the top picture here and that solenoid is turned on and it shuttles that shift valve over to the left you can see that line pressure comes in and is blocked by this spool right here on that valve it can't go anywhere so that's the position of the valve when it's in first gear now when we want to shift the second gear we turn the solenoid off and now the spring is able to shuttle that valve because there's no more pressure on the right side of that valve so that spring is going to be able to shuttle that valve over to the right and you can see i just opened up my drive pressure to the 2 3 passage i haven't mentioned it already but anything that's colored in red is considered line pressure and that's the greatest pressure that's the highest pressure that's in the transmission at any given time so on this top image you can see that line pressure is just basically waiting right here at that shift valve waiting for the up shift to occur and then after the shift occurred now it's directed into that clutch circuit we're able to apply that in this case the intermediate clutch and get second gear to apply so these shuttle slash switch slash shift type valves or whatever you want to call them they're controlling the direction of pressure but they're not responsible for controlling pressure itself they're just controlling the direction of pressure now this is all a little confusing it's it's because it really it kind of is confusing and this is just a basic lecture and i'm getting in a little deeper than i probably should on something that's basic but i kind of feel like i can tease you guys into some of this thought process here because we're going to get into it more in depth every transmission that we go through so even though it might be a little confusing now don't let that discourage you because you're going to hear it again for every transmission we're going to be talking about how valves work specific to that transmission this is kind of generic because we we do need to know that these valve bodies have shuttle valves or switch valves we do need to know that valve bodies have pressure regulators and we also got to know that solenoids play a big role in controlling pressures and and shifts and these transmissions and then we're also going to need to know what accumulator does so these are like the basics of what a valve body or what the hydraulics are involved with on automatic transmission but the specifics like how this valve works or how that valve works you'll get more of that when we get to these transmissions and we cover specifically how they work a regulator valve is going to just regulate the amount of pressure in a circuit like this one right here this is our torque converter regulator valve and it regulates the pressure that goes to the torque converter but mainly the torque of our clutch and the second one is the actuator feed limit and it's a fancy name for the pressure that we deliver to our solenoids so that way we're not hitting our solenoids with 200 psi pressure or you know whatever we'll actually regulate it to a to a maximum of 115 psi and then this regulator valve right here this last one that we'll talk about is the accumulator regulator valve and it is going to regulate the amount of pressure that goes to our accumulators which we'll talk about in a second so looking at the first one here the torque converter clutch regulator valve normally i have a solenoid that's right here the solenoid is going to work on the end of this valve i don't know what happened to solenoid i lost it or something but so as the solenoid energizes and allows fluid to go through it line pressure that would be present here and you can see it can't go anywhere when i energize that solenoid i'm going to open up the passageway and let line pressure find its way into the circuit the more my solenoid pushes and works on the end of this valve the more pressure that i'm end up letting in the circuit so what also happens is that pressure that ends up getting into the circuit is also going to be i'll come around here and work on the back of this valve with the spring kind of team team up joint forces with the spring to close that valve back off because these things will live pretty much with the valve in this position right here where the line pressure is just uncovering that passageway feeding the torque converter clutch circuit there because when i let more pressure into the circuit what will end up happening more line pressure gets in there not only does it feed the door converter clutch circuit but it also works on the end of the valve with the spring and it helps the spring close the back off once pressure gets high enough that is a a way that a solenoid can control a valve and then allow pressure to fill a circuit and basically regulate itself it's pretty common setup this one right here doesn't involve a solenoid it just involves the spring so the spring alone is what's going to determine what this pressure gets regulated at line pressure is able to come in through this passage this is the solenoid feed limit or actuator feed limit circuit where we're gonna have line pressure coming in and it has a way of getting over and then into the circuit that ends up feeding all my solenoids well just like the torque converter clutch the pressure that it lets in also is going to get around and work on the end of that valve so i have a good marker here for that so it's going to get around and work on the end of that valve so as pressure builds up in the circuit it's going to work on the end of the valve that's going to start compressing that spring and voila you get to the point where you block off the line pressure passage into the actuator feed limit circuit if pressure drops off in that circuit the valve moves over and allow line pressure to go back into that circuit as it goes back up closes itself off and this spring right here determines when that closes off so if i got a very strong spring it's going to take a lot of pressure before it closes off if i got a weak spring it's going to take just a little bit of pressure before it closed off and in this case it's going to regulate the it's going to close off once it sees about 115 psi that's what they don't want to see the solenoids getting much more than that now this last valve right here is the accumulator valve and it fills the accumulators up with fluid to allow the transmission to basically shift a little firmer if it's got accumulator fluid pressure in there it's got to squeeze that out when it shifts and that makes it a little stiffer during the shift so line pressure comes into this passage right here you can see it can't really go anywhere and then solenoid pressure works on the end of this valve this reaction land we call that area where pressure is working off of the reaction land or the reaction area so actually the fluid pressure that comes from the pressure control solenoid comes over and works on this valve so if i have pressure from my pressure control cylinder coming over working on that valve it's going to eventually it's going to open this passageway up here my line pressure is going to start going into my accumulator circuit and just like these other two valves the pressure that it lets in kind of comes over here and joins forces with the spring and that working across the surface area there it's going to close the valve land off and then if i want more pressure i turn my solenoid down more it's going to move it over allow more line pressure in until closes itself off again so i've got a variable pressure for the accumulators based off of what the solenoid the pressure control solenoid is doing on the end of this valve the more pressure i have for my solenoid the higher the pressure is going to be in this accumulator circuit and that's all adjustable by changing the surface area size on these reaction areas of the valve and also changing the tension on the spring so those are pressure regulator valves commonly found in a valve body they're not all found on valve body sometimes pressure regulator valves like for the pump might be found in the oil pump sometimes they are found in the valve body but in this case they're on the transmission that we're looking at here that's actually the pressure regulator valves found in the pump not in the valve body constant pressure type pressure regulator valve is really going to limit the pressure to a certain amount and not let it climb above it and in this example here this is an example of the actuator feed limit valve that valve is pretty common a lot of transmissions will have a valve they might call it something different like a modulator valve sometimes you'll hear it referred to or a solenoid feed limit and what it's doing is it's preventing fluid from fluid pressure from exceeding a certain amount and i know in this example right here this is the one that we used in the in the on the bench and it's limited to 115 psi and the way they limit that is by adjusting the tension of the spring right here so that spring is going to have a certain amount of tension that that once we have 115 psi present on the end of this valve across that surface area right there we're going to work on that valve with enough force to move this valve over to the right to the point where it ends up blocking off the line pressure meaning line pressure can't get into this circuit anymore so normally with no pressure in the transmission this valve is going to be shuttled all the way over to the left and it's basically almost can be positioned all the way over to the left we're going to have open access right from our line pressure into this actuator feed limit fluid circuit and that's what it's going to feed that circuit as soon as this engine starts up and it spins the oil pump in the transmission and builds up pressure in the transmission at a point and it won't happen at idle because like most of these transmissions will idle at like 60 or 70 psi so it'll actually still be wide open while this transmission is basically sitting there with no load on it as soon as the vehicle is accelerated or if you put the transmission in reverse and the load goes up well the computer is going to respond by saying we want more pressure in the transmission so the the transmission pressure the line pressure in the transmission the red it could be let's say climbed up to 200 psi well we know we don't want that going to our solenoid so what happens is that 200 psi tries to enter into the circuit and once the end of this actuator feed limit valve sees 115 psi there's enough pressure in this against the end of this valve to move this valve over to the right to the point where it blocks off that passageway and we don't get any more fluid in that circuit so the max that this orange fluid pressure can see the maximum pressure will never see above 115 psi no matter what the transmission does so if line pressure is at 60 it'll let all of it in so really we could say that the pressure that's allowed in this actuator feed limit would be between 60 and 115 but once the transmission pressure goes above 115 this valve's in a position where it won't let any more line pressure into that orange circuit or the actuator feed limit circuit so it does so by like i said regulating up against the end here we've got a spring with a certain amount of tension on it and we have this reaction land right here that's the surface area that this pressure is going to be working off of and that surface area is going to determine how much force is on this valve and once we get enough force to overcome the tension of the spring and move the valve into the position where it's going to block off that passageway then we've regulated the pressure and it won't go any higher also it's worth mentioning that there's an orifice feeding that reaction land so you could see that's what this choked down area in this illustration is it looks like they've got this uh like they narrow the passage there and they do they they these orifices are located in the spacer plate in the transmission when you take them apart you'll see it when you pull a valve body apart there'll be a metal plate between the case and the valve body they've got all these little holes in there well this is gonna be one of those holes that orifice and they put it that orifice there for a good reason they don't want the pressure change to overreact the end of this valve so if they force that pressure to go through this tiny little hole that orifice the action that's going to occur on the back of this valve is going to be dampened we're not going to see the pressures climbing and releasing fast they're going to be dampened out because everything's got to squeeze through that little hole so that kind of works is like a shock absorber a damp dampener so that way we don't over react this valve and cause it to turn move back and forth quickly because when this thing's operating and it's regulating its pressure the the position that you see the valve in right now is pretty much the position that it wants to live in where it's just letting enough of that pressure into that circuit and if it goes a little higher it's going to move that valve over to the right block itself off if the actuator feed limit pressure drops down a little bit the spring will overcome the the pressure in the actuator feed limit circuit and i'll cause it to move back over to the left a little bit more in so what i'm trying to get at is that that valve is pretty much going to be oscillating in that one little area most of its life and that's the reason why when we look at these valve bodies and inspect them all these pressure regulator valves are are the ones that we have to pay close attention to because we realize that they're sitting there buzzing back and forth in the same spot most of their life and if there's going to be anywhere it's going to be in that specific spot and you can see you can imagine the wear in these types of circuits could could cause some serious problems if i wore the valve land here the pressure that i let into the actuator feed limit could sit there and drain out through the exhaust and then i'd lower my overall actuator feed limit pressure and that wouldn't be good so but this is just the basic lecture we're really just my intention here is just to try to introduce you to these pressure regulator valves and these circuits get you kind of familiar with looking at these hydraulic schematics and looking at the valves and understanding that they all have a certain purpose and when we carry that over that information over to the units that we go through and maybe find some common failures within some of those units we might be able to narrow it down to a valve in the valve body that's wearing out or something like that so we just got done talking about a constant pressure regulator valve where we're going to limit the pressure to a certain amount and not let it climb above it and there are also pressure regulator valves that are variable that actually can kind of a moving target for pressure if you will and this is an example right here this is a line pressure control solenoid that we have if you look down there it says line pressure control matter of fact it might be a little familiar from the previous slide if you remember the orange fluid that is what's feeding that afl coming in and if you remember it's going to be anywhere between 60 and 115 psi because that's what that valve did is it it regulated it to a maximum of 115 psi and a 60 is the low end of it because that's pretty much the low end of the pressure in the transmission in this example it could be different for different transmissions but i'm getting a little more specific than i probably need to but so the solenoid can take that pressure coming in which is going to be a maximum 115 and it could basically deliver between zero it can block it all off and then allow as much as 115 psi in that circuit if you look to see where that pressure goes it finds its way to the bottom of this pressure regulator valve so that means that the base of this pressure regulator valve i can add anywhere between 0 and 115 psi so basically i have the ability of adding tension to this spring because the spring that i have in this pressure regulator valve right here is going to establish the minimum line pressure in this transmission and without getting too much in depth on how this transmission and this pump and all that stuff works we still have a reaction area of the valve so that there's going to be a certain amount of fluid pressure pushing down on that whatever the pump generates is going to generate line pressure and as that pressure starts increasing that pressure is going to be working on this reaction land the end of that pressure regulator valve if you imagine that's going to push this regulator valve down as it's drawn and it's going to compress the spring and once this valve comes down to a point it's actually going to open up a passageway called decrease and when it goes to decrease it's actually going to reduce the output of the pump and then we won't climb pressure anymore and now you know we're here really to talk about how this thing can vary pressure and how just pressure regulator valves in general vary so how does it do that well the tension of the spring is going to be minimum let's say the minimum pressure will be 60 psi and i will compress this valve to the point where i'm letting that line pressure enter the decreased passage at that point my pressure can't climb any higher in the pump now what if i need more pressure than that well basically i need to somehow change the tension of the spring to require more line pressure to move the valve into the position where it decreases it where does that additional pressure come from comes from my solenoid and it pushes on the bottom of this valve so the more pressure i have on the bottom of this veil the more this force in addition to the spring force the more force is pushing up on this regulator valve and then the more line pressure i need to push the valve down to get to the point where that limits the pump output so like i said without getting into too much depth on how this pump works realize that variable pressure regulators do work they're out there there's many transmissions have them a lot of times they vary their output from a solenoid feeding the end of a valve or a portion of that valve and influencing how much force is required to overcome not only that spring but this additional pressure and that way we can have a moving target as far as what our pressure overall pressure is going to be in the transmission so those are the two different types of pressure regulator valves that we'll see in most transmissions one thing that's worth talking about here are these accumulators so i've got two accumulators in this valve body a lot of times accumulators are built built into the case or there might be a separate valve body that has accumulator pistons in it on this transmission they put two accumulators in kind of built into the valve body or bolted to it from the bottom this one's used for a third and this one's used for fourth so when fluid pressure when you shift this transmission from second to third so the pressure doesn't just go from zero to 150 or whatever psi they put in the oil passage for that circuit an accumulator piston this accumulator piston will then provide a place for fluid to go while that clutch is getting ready to apply so if you imagine the fluids on its way after the shift valve moves and the fluid is on its way to the third clutch direct clutch what's going to end up happening is that fluid is going to find its way into this circuit and it's going to compress this piston up when it compresses this piston up it's going to squeeze the fluid out and then when we shift from third to fourth the similar thing is going to happen on this accumulator full pressure is going to get underneath this piston and it's going to push this piston up compress the spring push the fluid out by doing that we allow these transmissions to have smooth shifts not all transmissions have accumulators a lot of newer transmissions they don't they don't have accumulator pistons in there because uh they're able to control the rate of apply using electronics and it does a pretty good job they do still use accumulator pistons on some transmissions you can see on this honda that is extensively using electronics they still have some accumulator pistons in there this is off of another honda six speed and they have an accumulator piston right there this 6l80 valve body though is an example of a transmission where they don't use the accumulators anymore they just use extensive use of their computer controlling the clutches through the solenoids so in summary valve bodies use shift valves to control the direction of fluid flow pressure regulator valves to change the amount of pressure they use accumulators to cushion or dampen clutch or band application and they also use solenoids to control the position of the valves or to control pressure at the valves you

Channel: siu automotive

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Length: 34min 6sec (2046 seconds)

Published: Sat Aug 08 2020