Lockup strategies and their affect on clutch durability.

In the old days we swapped 350s, 400s, C4s, C6s from car to car, as long as you matched for correct engine (v8, v6, 4, etc.) with the only thing needed being maybe a vacuum modulator type swap out and a careful adjustment of the same. And even in a mild performance application, the only thing needed was a simple valve body recalibration kit, that mainly just provided increased overall line pressure and feed to the friction elements. There was no need to customize certain holes in the separator plate to make sure line pressure rise matched the engine torque curve. Following manifold pressure was accurate enough. There are certain instances, as with anything, where the vacuum modulator system is a problem, but for the most part, that is rare. I have never had to resort to a cable on a vacuum modulated trans, although I realize they're available or used to be (B&M). I have had to use simple devices to control the vacuum signal (blown applications).

Looking at the cable system in modern transmissions, as Chris has already shown, each and every valve body bore, valve, valve spring and separator plate orifice is specifically matched to the engine it will be mated to in a production vehicle. When you swap a transmission that is so highly calibrated for one specific application, you can run into problems real quick. The easiest way to get around this problem is to install a valve body recalibration kit that will make the transmission a more universal fit. Then the problem arises where sometimes the valve body recalibration kit doesn't quite blend in with a particular OEM calibration and now your either removing the recalibration kit or correcting it. As a trans tech in the 80s, it was common to see revisions or changes to valve body recalibration kits as the manufacturer of the kit attempted to address kit installer's complaints. At one point, when you called tech support about a problem, they wouldn't even answer the phone. In essence, you became their R&D department and when they got tired of hearing the same complaints, they just wouldn't answer the phone. They were to busy adjusting the kit. I can't say for sure this is what was happening, but from my perspective, that is how it appeared. Soon other companies came out with simpler kits that gave more acceptable and consistant results. Again, to go back to the old 3 speeds, I would completely disassemble a 350, 400, C6, TF valve body, throw everything into a basket, run it through a cleaner and assemble them blind folded. That was because you could count on every valve and spring being very close to the same configuration from VB to VB. It was a much simpler time.

Back to the thread subject. How many people can identify the size of their torque converter's clutch friction area and the other factors that will determine the life of the TCC under different torque loadings? Why don't we get a listing from everyone of all the different T/Cs that are being used or any that people would like to use.

That brings up an interesting question that I've always pondered. I have heard that when you lockup the TCC under high load, the stock intermediate shaft has a higher tendency to snap. Is this correct? And if it is, might it be because of the OEM dampener assembly bottoming out and in essence hammering on the input? The OEM dampeners are only rated for a relatively low torque number and can easily be bottoming out with the mods done with these engines. If a strong enough dampener assembly could not be found or developed, it would make good sense to eliminate it so that it can't turn into a jack hammer on the input. I am aware that some aftermarket T/Cs have eliminated the dampener assembly. Let's include those in out list.

I'm happy that you've had such good luck with the OEM TCC. I know of others that have claimed the same results, but I also know there are others that have not. Maybe we can explore why that might be in our discussion here. Those of you that have used the OEM TCC and locked up under high load, how long did it take for damage or slipping to occur with the TCC? And please include the circumstances of your lockup strategy if you know them. Grumpy, when exactly off the line did you lockup? What gear?

I just locked the converter on the line so when it hit second it was locked .. otherwise I would forget ..and then manually shift 2-3rd .. like I said I have been beating the crap out of stock converters since 86 on my first GN . I have broken say 5 drums .. but thats since 1986 .. not that bad for stock POS drum .. I can't believe the beating these trannys take !!

I'm willing to bet that locking up the TCC while still in first gear is much less of a load on the lining than it would be if you locked up just after the 2-3 shift. What do you think? Maybe that's the difference in durability? Maybe the gear advantage in first and second versus 3rd has something to do with the amount of torque load or length of time the torque load is being transferred through the TCC. Hmmm.

Time slip wise, what was the improvement you saw by locking up versus not locking up.

Another thought in reference to the TCC dampener assembly, if the damp assm is bottomed out during the 2-3 shift and any rotation reversal occurs in the geartrain, the dampener would unload. Then when the geartrain snapped back to normal rotation, the dampener would bang back to the bottomed out position. There's that jack hammer again.

For those that are lost by the rotation reversal, the 2-3 shift is a syncronized shift which is why it's easy to experience a flare or bindup feeling during that particular shift, depending on different wear or assembly factors going on in the transmission. Have to go. Maybe one of the other techs can explain to the rest of us what a syncronized shift is. If not, I will when I get back to the board.

i used a stock gn converter with a 9.2 :1 406 with a 144 bnm blower and locked it in 2nd gear at wot for i year without issues.i would pull 70 mphour on the bronx river parkway and lock the converter in second and run the car up to 140 mphour locked .periodic checks revealed the converter only ballooned .012" after putting 3500 miles of abuse on the motor.the stocker is pretty tuff in the clutch department with the dampner .if you remove the dampner itll destroy the front cover of the converter without a reinforcement plate present.this should say that you are safe at 400 horsepower with the converter if you lock it up at wot as far as the clutch is concerned however the fins will usually fold over at 300 horsepower in most applications.ive been lucky too i guess.the question we must ask now is at what power level is it ok to lock the converter at wot for best et and durability based on how much power the engine makes.if your below 400 any rpm that you jump the aldl and improve et and mphour shouild be the answer.don that reversal of direction caused by the planets rotation is pure nonsense.before making such a statement study the held and driven members of the trans and revise your statement.

I always thought that the dampener was meant to absorb engine tortional vibration so that it is not transfered to the input shaft giving a smoother ride from the drivers perspective. Identical to the function of the dampener on the clutch disc of a standard transmission setup. You will need to educate me in how removing it will destroy the front cover of the torque converter. Am I wrong in the statement that some performance T/C manufacturers are removing the dampener with no adverse side effects? TCS?

Explain to me the fins folding over at 300 HP. I can't recall ever having that problem. Usually, needle roller bearing failure or TCC clutch. Even one way clutch failure is rare. Have you experienced that much pump fin failure?

In my next posting, let me try to explain what I phrased as rotational reversal (never said anything about planets). This relates to the syncronized shift I eluded to in the ealier post.

the converter clutch pressure plate is fixed via splines to the turbine assembly which drives the the input shaft .it is held or locked to the cover assembly when converter off oil is evacuated from the rear of the cover.the damper controls absorbtion of apply force (much like an accumulator in a clutch or band apply circuit)transferred to the front cover and input shaft to eliminate the failures and other operating concerns when pressures are not transferred in amounts proportional to the safe design limits of the specific material or materials involved in power transmission.in other words removal of the dampner without the addition of an anti distorsion device(billet cover)added to the cover will cause distortiom of the cover as well as shock load the input shaft in high gear due to the operating conditions in direct drive placing the load of the vehicle ,tires,rolling resistance,differential ,etc on the input shaft during lockup because everything from thye crankshaft to the wheels is locked together in unbiased ratation.(gear sets in reduction absorb forces transferred thru moving parts spreading operational load through more parts ).with a vehicle stationary and in gear fins in the d5 in unmodified condition will bend over when subjected to the forces imparted from on the blades from the pumps oil passing thru the stationary stator at which point it is capable of multiplying engine torque to more than twice its original input rate.now if you read the original question we have enough info to know that lock up strategies for maximum performance and durability are directly dictated by the power of the engine and the mechanical limitations of the parts in question after the optimum zero coupling point is found.

thought it would be interesting and informative to investigate the affect that different lockup stategies would have on the durability of torque converter lockup clutches of differing designs. Stock, multi-disc, small diameter, etc. This would be of particular interest to people thinking of installing a modified computer chip, but are still running the stock converter. Is this a topic that would be of interest to anyone?
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Donnie Wang

DRW Transmission and Auto Care
84 GN with a BAAAD alcohol and nitrous habit
Ultimate Stage I
9.28@146.99
http://www.drwtransmission.com

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I have to differ with you on the function of the dampener. It is designed to dampen tortional loads only, not oil apply force imparted on the TCC piston assembly. In fact when you study the hydraulic circuit of the 200-4R, there is no provision for apply pressure accumulation. Apply feel of the TCC is controlled mainly, but not solely by an orifice located in the check ball capsule that is located in the front tip of the input shaft. It controls the exhaust rate of the fluid between the front cover and the TCC piston assembly. One common trick to firm up TCC apply is to remove this checkball capsule, thereby quickening the exhaust of release oil and in return quickening the apply rate of the TCC piston. That has got to be clear, since we are talking about TCC operation here.

Your correct about loads imparted on the stator and turbine fins in the torque multiplication mode, but I just haven't seen fin failure to be a big problem at such a low HP level. That isn't to say that others have experienced differently.

Chris brings up a very important point about the zero coupling point. Does anyone realize how soon this point actually occurs during a run down the track.

If anyone is interested in me explaining the syncronization that occurs during the 2-3 shift let me know. Otherwise, I'm going to save on the typing.

In a previous post I mentioned how companies that market valve body recalibration kits can use the consumer as their R&D department. That is a very important point to keep in mind. In the coming posts we'll explore the different methods available to companies that market a new product to make sure it will do what the consumer expects it to do.

regardless of its intentional purpose it does affect tcc apply feel when it is omitted from the converter.just looking at its position in the converter and what mechanical items are on both sides make this readily apparent.a scientific phrase comes to mind"for every action there is an equal and opposite reaction.regardless of what you may hink to be factual ,the omission of the dampner firms up apply as does the omission of the ball and the solenoids ability to seal pressure.line pressures over 250 psi become a problem for the lock up solenoid.although the rate of apply is controlled by oil flowing on the turbine side the mechanical items present in the converter affect feel and apply energy absorbed or lost as well as imparted during apply.a 100 percent link means all are connected ,this should also infer certain other mechanical principle.you disagree thats fine ,get back to the topic.lock up strategies and there affect on clutch durability.and yes ive seen turbine fin failure on several d5s and we have converter equiptment in house to verify these things are present when we cut them opem

Let us end the subject of the torsion damper with the definition given in the Bosch Automotive Handbook. You all out there can interpret it any way you choose.

In reference to a torque converter lockup clutch, 'As far as basic principles are concerned, both the layout and the operation of the torsion damper correspond to those of the dry friction clutch.'

In reference to a dry friction clutch, which is the typical standard transmission type clutch assembly, 'A single or multi-stage torsion damper, with or without a predamper, may be integrated in the clutch plate to absorb vibration.'

Ok, let's start putting together a listing of different torque converter configurations. Anyone out there? Come on now. I'm doing this because some complained that I didn't finish this thread. Let's see some participation. I do have other things I could be doing.

I've got a 10.5 L/U with 3000 stall from CK getting ready to go in my car.

Rick

Hi Rick, thanks for stepping up. Lets start putting together a specification list on your particular T/C. We'll try to use specs that we can gather from other models for direct comparisons. Chris may be able to help us. He stated that he has the capabilities to cut open T/Cs. His help would be invaluable. Lets start with the following short list.
TCC lining type.
TCC lining ID.
TCC lining OD.
The ID and OD dimensions will allow us to calculate the area of the friction surface.
Single disc or multi disc. If multi disc, how many.
TCC piston ID.
TCC piston OD.
This will give us total apply piston surface area available.
Piston area and friction surface area will give us an idea of holding ability of the TCC clutch. The friction material type will also have to be factored in.
Does the T/C use a damper? In your case, I would guess it does.
Billet cover or OEM style cover.
Number of mounting pads or mounting holes.
Mounting pads integral with cover? As would be the case with a billet cover.
Lets start with this and see how well we do gathering this info.
I will work on this list for a OEM D5 converter and maybe Chris can also give us some info for a typical GM 9 inch converter. The type usually used in a FWD application and modified for use in a rear wheel drive application. Old technology, but it would be helpful to have the data for comparison.

OK, let's get to work.

don ive already presented my info,and find youre veering off path here .why dont you look for those answers in your bosch automotive handbook.i see what your doing here and i have no interest in continuing this any further.you started the thread so its all yours.i have yet to be impressed by anything youve presented and see you have a history of not completing things,i operate differently.not finishing what you started is a sign of an underachiever,dont let yourself fall under that category unless you belong there.

Well they say great minds think alike, doesnt seem to be true in this case..I must say I have been following this thread for some time now as I am gearing up to do upgrades to both my torque converter and trans..you both seem to be very intelligent, and yet as I read your posts I find myself wondering why such intelligent men would spend their time argueing back and forth with each other.I personally am wondering what is it about these buicks that have professionals in a tiff with each other? I live here in sandiego and I know that there has been a time when opinions have made friends go their seperate ways..But lets try and remember that this site is here to help one another.And for people like me to try and learn and get some guidence from some of you more knowledgeable experts..I thank you all in advance and I apoligize for interrupting your thread and turning it into a group session..P.S I just want to be smarter and faster than the average bear...(oh to dream)

I'm truly sorry to hear you feel that way, Chris. Together we could have presented some very interesting info for the others. I quess I'll work on this myself. No hard feelings.
Maybe some of you out there can contact your converter supplier or prospective supplier and get some of the info for the rest of us. If you give some supplier names and converter models, I'll do my best to make some contacts and get this info for you.

Here's mine, see what you can find out.
Precision Industries 9½" Vigilanti muti-disc ( 5 disc ) lock up, " 6 " pump configuration

Hi Donnie, I'll do my best to get that info for you.

Let me make some things perfectly clear here before we go any further. This is addressed to all viewing. My presence here on the transmission talk section seems to be ruffling some feathers. I'm not sure why that is. My objective to coming to this bulletin board serves two purposes. One is to learn from others and two, is to convey some hard learned knowledge to others. Some clearly think that the only reason a business owner comes to a bulletin board is to try and sell product and/or service. In my case, that is the farthest from the truth, and those of you who know me well can relate. The very core of me is auto lover, racer and I love studying engineering of any type, automotive, aviation, and any other fields that supply technology to both. Never attended any formal engineering classes. The little bit of college I dabled in was a disaster. All I could do was day dream in class about the next modification I could do on my car when I got home after class. I'm sure some of you went through the same thing. Anyway, I love to study anything that has to do with automotive and particularly high performance automotive, not foresaking the ultimate F1. I like to apply what I learn to my car projects or at least, what I can afford to. I had no idea I would end up with a Stage I engine with the exhaust tone of a formula car. I have to say, I find it to be very cool, and this just fuels me on to the next car or engine project. Some of you think there is some alterior motive to this thread. There simply isn't. It is to study the black art of torque converters. Nothing more. There has been a lot of background info that has been written out that I felt was necessary to get most up to speed in understanding the workings of transmissions that will hopefully not be wasted in future discussions on this thread. If it has bored some, I'm sorry for that. I am a very detail oriented person and I can go overboard very easily.

One more thing that I want to add to hopefully relax some of you. Today, I am instituting a firm policy at my shop. The service manager will be informed of this policy. Our shop will not sell any service or product to anyone who comes to us saying they were referred to us because of this bulletin board. You will be turned away if that is mentioned. I'm just as much a car nut as any of you and I prefer to be treated that way. You will not catch me promoting my business ever on this board. You also will not catch me ragging on others who may choose to promote themselves and/or their business, and rightly so, on this bulletin board.

I hope we can start having some good dialog from here on.

One more thing, and I hope this doesn't disappoint. The shop is very busy at the moment, so it may take a few days to start gathering some of the info on the agenda. Thanks. Anymore models to go on the list? TCSs piece seems to be very nice. Maybe Bruce can give us some details on that unit.

Hi Don. I helped revive this thread because I don't think one can have too much knowledge. I am a novice when it comes to this stuff, but very much like the insight and expertice you have been kind enough to share with us. As well, being a novice, your easy to read text is very helpful. Thank you.

I have a PTC converter from the guys out in Alabama, and had requested that as they built my converter, that they snap a couple of pics along the way. They had already built mine by the time I had made the request, but they did send me some pics of a 10" converter which is pretty much the same as mine, except built for a Ford. Since I don't believe they typically give pics of the inside of the converter, and becasue I didn't ask permission, I won't post all of the converter pics, but here are the pics of the lock up clutch and damper. Since we know the outside dimensions of the converter are 10 inches, we can interpolate the dimensions of the clutch and friction. My calculations, by comparing pixels to inches, shows that the plate is about 9 inches, and the friction material is only about .75 inches wide. Certainly not much meat on there. A lot less than one would expect. I guess this is why many prefer the billet covers to the stock covers.

Thanks for the words of encouragement, Firechicken. The OEM covers do limit how wide one can go with the friction plate, or friction strip as you can see. The friction strip isn't much wider than a typical OE, if that. It looks like either a modern high energy lining or maybe kevlar. See if your supplier can give you some description of the lining material.

Forgive me if I've already gone over this. I want to go over what is involved in a clutches ability to remain engaged without slipping. The variables are as follows;
Clutch apply piston area. The larger the area, the more pressure that is transferred to hold the clutch. For instance, if the piston has 10 square inches of area and you have 40 psi of hydraulic pressure acting on the piston, then you have 40 x 10 = 400 lbs of force acting on the lining. If the piston has 20 square inches of area and you still have 40 psi of hydraulic pressure acting on the piston, then you have 40 x 20 = 800 lbs of force acting on the lining. The more force acting on the lining, the better chance of no slippage. The general result that we can get from this is, the smaller the overall torque converter diameter, the smaller the TCC apply piston area and the better chance of TCC slip when compared with a torque converter of a larger diameter. This is only one consideration.
Lining size. A lining with more area will hold better than a lining of less area.
Lining material. Different material types have different coefficients of friction. A dynamic coefficient of friction has to do with how fast a particular lining can cause a clutch to come to a complete clamp after application of the clutch is initiated. Static coefficient of friction is a particular linings ability to hold clamp and resist a force trying to cause it to slip.
Fluid type can contribute to the coefficients of friction described above for the worse or better depending on whether your looking for a harsher or softer shift. Type F fluid and racing fluid types are typically known for causing a harsher or quicker shift.

A small diameter torque converter with a large friction lining area can hold as well as a large diameter T/C with a small lining area.

If we know that a T/C has a relatively small TCC piston area and low friction area, that will greatly affect our decision on what type of lock up strategy we're going to use.

It's pretty easy to say that a multi disc T/C has it over most single disc T/Cs as far as TCC holding ability goes. There are some inherent peculiarities associated with multi discs that make the decision to use a multi disc difficult for some.

One last point for this posting. Piston area (square inches), lining area (square inches) and hydraulic pressure in the form of psi (pounds per square inch) are the three main factors that dictate a clutches clamping ability. When working with a band servo or clutch pack in the transmission, all three of these factors can be manipulated to affect a clutches clamping ability. With a torque converter, you can only play with piston area and lining area. The hydraulic pressure from one application to the next will be pretty close to the same. Usually, around 40 psi. This pressure should not be modified to a higher value. Torque converter internal pressure that is too high can cause a worn crankshaft thrust. This is something to keep a close watch on with the Turbo Hydramatic 400, but that is another story.