Ok, so I'v been working on my loader here lately trying to address some various problems i'v been putting off. After posting some questions relating to my issues at hand a couple gentlemen suggested looking into my torque converter. Now I'm not saying there is anything wrong with mine and neither am I denying there is, that's neither here nor there to this particular thread. I am more after some general knowledge about '' thee '' torque converter in general. I believe I have a general theory of how a torque converter works, but I want to know exactly the purpose of each component. Lets just say if I was a cat my nine lives would have ended along time ago as I am a very curious person. My main interest would really be in how does a torque converter fail ?!? I'm sure each and its own has its own weak points in design, but from my understanding theres not much in one to really fail The propeller(apart of toque housing) thrusts hydro fluid against the turbine (causing rotation much like a pin wheel being blown in the wind) after passing through a stater and returns there after in an never ending cycle. I also assume the torque locks up directly by a clutch once reached a certain RPM. What makes the clutch lock up ? A certain pressure point within ? The revolution speed it's self ? Why is the torque converter pressure regulated ? For proper flow as a coolant purpose or a lockout purpose? Forgive me if this has been talked about many times again, new to the forum and still learning to search correctly. You would be surprised to know how many people know nothing of a torque converter and how it works, so any knowledge for me and them would be of great appreciation. Thanks in advance. Digging the forum by the way, there is some really knowledgeable people here, I am sure to learn alot.
2 main causes of failure are No one changing oil and filters and screens :beatsme Guy in the seat roasting it. oil breaks down with heat and looses all its lubrication propertys. converter has 3 main elements, plus the housing. impeller driven by engine. turbine connected to output shaft. and stator which directs the energy imparted from the impeller to the turbine back to the impeller which is what gives you the more 'push' torque converters typically raise the input torque supplied by the engine anywhere from 2 to 3 times. Even as much as 5 times on some converters; ie most allis chalmers ones. the downside is a loss in fuel efficiency. Also converters do not lockup unless they have a lockup clutch fitted. this effectively locks the engine flywheel to the turbine to give direct drive, bypassing the converter.
D6 Merv> This is exactly the kind of info I'm after. So not all torque converters have a lockout clutch ?!? This is why I posted because I assumed they all did.. And what exactly fails or wears by not changing the oil and so On, the turbine blades themselves, or the viscosity break down of the oil ?
the bearings wear or fail mate; then things rub together and make metal; causing heartache stress and large amounts of dollar bills to evaporate; as well as sending men to drink and ruination :beatsme converters are one place where abit of preventative maintence can save you a lot of money. Along with having someone intelligent in the seat and not a mushroom. Nothing helps to focus operators and/or owners ! thoughts more than the thought of having to fix it or pay for it yourself :notworthy
D6 Merv, Thanks for the info that is so well put. So what does a good maintenance schedule entail for a D6 dozer for example? How often or after how many hours must you change out the engine oil and filter? The transmission oil and filter? Hydraulic oil, etc? What else should the operator be aware of, apart from following the schedule to the letter? Do the schedules vary from D6 to D7, etc? Madozer.
most cat maintence schedules are similar. My D6 is like this engine oil and filters every 250 hrs. fuel filters 500 hrs. trans filters and screens 250 hrs, oil every 1000hrs hyds. filters every 500 hrs, oil every 1000hrs final drives oil every 1000hrs the 250 hrs intervals make for easy intervals to remember; oh and you usually have to drive a grease gun for abit each day too; quite amazing all the people who can tell you they can drive a $250k plus machine but are incapable of driving a $100 grease gun :beatsme
cat and most equipment manufacturers have operations and maintence manuels outlining all the maintence points and intervals for each machine
Rather than go deep into it, what machine do you have..? I assume it's a dozer because you are posting in the dozer section. A couple of comments about torque converter failures. The most common failure mode is failure of the roating seals inside the converter. The oil that eventually finds it way into the cavity containing the impeller, stator, and turbine gets into the "guts" of the converter via passages in the centre shaft. The passages have seals at both ends to stop the oil falling out. The most common cause of seal failure is the converter being "cooked" as Merv commented above. The other failure mode is bearings and that is usually (but not always) related to poor maintenance and the quality of the oil that has been lubricating them. Other than that they are generally pretty reliable so long as the oil and filter is changed at the appropriate intervals. Very few dozer converters have lockup clutches. I think some of the larger Komatsu models do but I am not exactly sure which ones. There is really no point in having lockup on a dozer unless it's being used for 200yd pushes all the time.
FTR, this regards a 2,000 hr, pristine, Case 450C that has loss of power, smoke and higher torque converter temperature at about the same time.
A lot of converters do have sprag clutch bearings in them to cause lock up under driven conditions. tctractors
Does the engine lug way down lower under load since this happened? Will the machine roll down a grade as freely as it did before? Later Bob
Bob/Ont > It does lug down when under load but will not turn(spin) the tracks when up against a stump or somehting similar,It just stops with the engine bogged down., it will roll down a hill as it always has, the engine holds it back as the machine draws on the engine. But if the engine is shut off it fust takes off freely. Nige > my machine is a Case 450 track loader/dozer. From my understanding the tractor itself is the same as the dozer, just with a dozer blade instead of bucket, so i always post in the dozer forum as there is more info there than what i have found under track loader. From the repair manual i do not see any clutch packs within my converter, so i believe you are right. But that brings several other questions to my mind. If there is no clutch assembly in such torque converter, what causes one to slip ??
All torque converters slip by design, otherwise when you engage gear you would stall the engine. The fact that there is only a film of oil and no mechanical coupling between the impeller and turbine wheels in "converter drive" means that the turbine wheel is always spinning slightly slower than the impeller wheel. Even if you have the engine at full RPM with the transmission in neutral this will still be the case. For a torque converter with a lockup clutch the clutch locks up under certain conditions to give direct drive, generally when the machine is on the move. However if you were up against something "heavy and unyielding" your converter would be in "converter drive" as above.
Like Nige said, there's no mechanical coupling, so the better question is what causes it to turn? and that's the fluid, I don't know how, and it doesn't really matter, the important point is that slippage is very useful because the torque converter uses that slip to increase the torque when it's slipping. But it doesn't double the torque at half the speed because it also produces heat, and more heat at more "slippage". If you meant "what causes a torque converter to fail by slipping?", I don't know if they do that or not, but I believe as the oil gets hotter/thinner the characteristics of the torque converter change (when it's bitter cold there's more drag at low speed, more slip when hot, right?) but that would let the engine speed up, not lug the engine down with lower torque.
Sounds like the overrun sprag in the stator may be seized.That will make the converter into a fluid coupling,no Tork amp,and build a lot of heat.
If this particular tractor has a sprag clutch in the converter between the stator and the shaft, a failure of that clutch (thus allowing the stator to spin instead of being fixed on the shaft) would cause the engine to stall every time the transmission was put into gear.
Yair . . . Interesting discussion. In the 1950's when Converters and powershift became available there was some opposition to the technology because the machines could not be push started . . . so much so that when Allis Chalmers belatedly bought out their power-shift one of the touted features was that they had a sprag clutch and could be push started in reverse. Cheers.
Do you know if it actually worked? With the engine not running, there would be no transmission pressure. Therefore no clutch packs would be engaged even if you had the lever in reverse. Even if reverse was engaged, the 'reversing' is achieved inside the transmission. The torque converter still turns the same direction whether the transmission is in forward, reverse, or neutral. So how did a sprag clutch in the torque converter help with push starting?
Yair . . . Plant Fitter. We were lumbered with the first three powershift twenty ones in the country and that was one thing on them that did work. I'm unsure of the actual set up but I remember a ramp and roller set up in there some where (probably on the bottom shaft) and assume it drove a charge pump. The transmission was a three shaft two speed. The side to side movement of the lever selected speed and direction and the back and forth movement engaged a modulating clutch between the engine and converter. I seem to remember it took twenty or thirty yards to start, gear-lever in first reverse and then flick it back to engage the modulating clutch. Cheers.
Timberking if the torque stall speed is half of spec/ say 900 instead of 2000 the stator might have broken loose from the ground sleeve. If that happens the stator will not redirect the oil out of the turbine and it will hit the impeller head on and slow it down. That will over load the engine and give no driving torque. Later Bob
Most allis,s had a push start pump, you had to manually engage the pump that would provide oil to feed the control valve and select 2nd rev [this was on HD11 and 6] this gave drive pressure. All AC converters had a overrunning sprag clutch; this was bloody good as it gave downhill braking. When the output shaft speed exceeded engine speed the cams and rollers locked up giving direct drive and this was how you could push start them. Downside was it all made for a plumbing nightmare, especially when combined with ACs ground speed governor, which was just a bloody hard way of doing what we all do with a decelerator. Most people deleted all the push start and ground speed hyds, made them a lot easier to fix. But still difficult compared to cats simple layout like a D6 Incidently the early cat twin disc diesel torque converters also had the overrunning clutch; but cat bought out a product bulliten stating to remove them in the early 60s after the single stage oil converters became there standard p/s trans.
Yair . . . D6 Merv . Good one mate! I have mentioned push starting the power shift Allis's on other forums and copped a few snide remarks. (Big grin) It's a long time since I messed around with them and the details get a little fuzzy with the passing of the years. As far as torque converters go I think some folks don't realise those early setups had a conventional over-centre clutch in front of the converter which drove into (in the Allis case) a simple two speed gearbox. As you mention the early ones used diesel from the tank as torque transfer fluid the later ones ran oil in the converter and the clutch. The system worked well and I suppose was the reason Allis took so long to come out with a true power shift. I did a few shifts on a D8 with a fuel converter and it was an absolute dog . . . it appeared that torque converters work better at 2100 than at what? . . . thirteen hundred or something behind the Cat engine in the D8. It was a really strange sensation to see a couple of Allis's clattering along in light country pulling in second . . . foot on the decell to keep speed down and when the tracks stop feed it to her, no go? Slip her back into first on the rock back and up it again. They seemed to progress in series of jerks but in truth it was very smooth. Cheers.
Hey Scrub Puller, what was the model of the D8 that had the diesel converter fitted? Were these the early D8s that were built in Scotland? Remember doing a re-seal on one back in the early 70's when with the MOW at Twizel. Carbon face seals were used as rotating seals to feed the diesel into the converter. Not many have heard of these converters.
would have been a early 68A D8H John, these had diesel converter to start with, then later changed like the American 46A. We had quite a few of the early pom built D8s come to NZ. Remember doing a final drive on 68A22. would have to have been a fair chance it might have been a ex works one too.
Yair . . . Aussie John . There you go, D6Merv has confirmed it. I thought they were 68A's but I am pretty poor at remembering numbers . . . the one I ran had a seven roller track frame which was considered a bit of a novelty at the time. In the soft red country with the torque converter and (so they reckoned) the extra roller it was very unresponsive and didn't want to turn . . . completely different to the stick shift on the other end of the chain. Cheers.
Well I must say I wish I had not brought up the sprag bearing thing it seems to have made all 6 cylinders fire up, the lock up bearing was used by Komatsu in plenty of their iron, anyhow now the Diesel Torque has been dusted off I would like to say (already pointed out) that there was a single plate toggle clutch between the engine and the torque, the clutch was only engaged at low engine speed then the throttle was given the "Beans" and all was good and moving, if the clutch was worked (engaged) at high engine speeds with or without load the single disc would spit the dummy out very quick, this would get a fool like me to strip things down resulting with the pilot getting the lick em' and stick em' "Red Card" off the Slasher (Muck shift Forman) as in the right hands the diesel torque was a fair item that worked well with a pilot that understood the beast, the fuel tank liked to be kept filled 2 times a shift, not that it was an alcoholic it just worked better with a full tank, to drive 1 of these beasts was if you did not keep your head trouble coming fast, if you were pushing muck over an edge or into a hole as the load came off the blade the tractor would quickly speed up trying to send itself over the edge, so it would be best to say learners keep clear of them, the carbon seal was a thing needing carefull and often maintaining, they had a drip pipe off them that you where supposed to count the drips off in a given time, we used to have milk bottles hanging to catch the drips, when we swapped them for gallon cans it needed replacing, I thought the Glasgow built tractors fitted with the Diesel Torque had something like 52A series? I have never seen 68A tractors fitted with this style of drive, thinking back on things they were right "Dogs" but thats what we had, the other day I was told that I am "Old School" what is all that about? I had a hate for the place. tctractors p.s. there is a few snaps of a D8H torque that I refurbished the other day in the shop talk thing.
Yair . . . tctractors. As always interesting comments but I must say your mention of "babying" the master-clutch is some what at odds with the way we ran them. When pulling with two (or three) tractors inevitably they would stopped by a tree or trees and begin to spin their tracks . . . one machine often a bit in front of the other. The idea then was to manoeuvre and get the machines pulling level and up it again (usually with a bit of a bump on the throttle to make sure you had all the "Beans") when they got stopped again (if you had visuals with the other operator) with a bit of body English you sort of rocked forward and, in time with each other, disengaged the clutch. The tractors would rock back a little from the weight of the chain and the swaying of the tree. This was done three times and if the tree didn't come the tractors were backed up onto the little mounds of dirt kicked up by the tracks. The tree or stump was given three charges in this fashion, if it didn't come the inside tractor rattled back and pushed the tree or lifted the chain over the rock or stump. It all sounds pretty brutal (and I suppose it was) but the weight of the chain seemed to cushion the shock to some extent. At no time though was there any thought of studying the clutch . . . I can assure you though the adjusting ring never had time to seize. When the later series HD21's came out with the oil arse end, torque and clutch (for us) they were pretty trouble free in that department. Cheers.
Hi Tony yes the 52A was the stick shift torque converter model with the dry master clutch. They are a very rare tractor; only about a hundred or so were made. And none made it down here. the very first 68As #1 up to 82 had the diesel torque converter and early double gear torque divider. Was a few of these early ones made it to NZ Hope your keeping well and enjoying your UK summer. Is just wet cold rain and mud down here at the bottom of the world Cheers Merv :drinkup
Hi Merv, the Sun is like a big fried egg in the sky here with some off the scale temps, 30c has popped up a few times this week about 25c is about all we Brits are good for before we start to "Winge" anyhow back to the Diesel Torque thing as possibly I have been stuffing my rag in the wrong hole some? the 52A's that I used to tamper with also had a big sister a 19A chariot, they were owned by a right old style land clearing contractor that wore a tight collar on the hottest day, I have never seen a 68A with the Diesel Torque and fancy drive divider, all I realy remember was they needed lots of spanner work if the wrong pilot copped the ride, I can recall converting an 18A with the air blown brakes to a wet case, I had all the tech' drawings of holes to drill and tap and a box of parts to install plus loads of bits to remove to effect the modification, plus a good few days cleaning out the main case of brake dust ( I wonder if its still in my lungs??) well I supose this is a bit off topic but I can recall the 52A's being following serial No's the owner never bought them new, they were bought off a gravel pit local to me some years before I was allowed near them. tctractors
source of all problems Tony; the wrong pilot in the seat; some people couldn't drive a duck to water. Interesting about converting those dry bum girls to wet; have never heard of that conversion on D9Ds and Es. 19As were a popular pusher tractor over here. 30c is just nice for me; barefoot and shorts weather, and I drove dozers in that attire too when I can. Not much osh bulldust where I am. Although has changed a lot for the worse in last ten years. cheers mate :drinkup