Dual disk clutch does not shift slower than a single.

[wsucummins]

GREAT THREAD!!! one of the most informative ive come across. I do have to say though. Thank you MD for making upgrading my auto look so much cooler and more fun on the road I will never again think about doing a manual swap

[joefarmer]

I just had to!

I didn't realize the HMR Street Drag was a diaphragm style pressure plate. It looks lighter than a McLeod lever style, does anyone know weights?

[JakeDiesel]

I learning so bear with me.
I was looking at some of the dual and triple disc clutches and they say that you cant shift above 2000rpms is this because of the added weight, that is what i am understanding but not 100% sure

jake

[roachie]

Those triple and DD's your seeing are weighted. Centrifugal force causes weights to apply more clamping force to the pressure plate. When those weights are out you can forget about mashing the pedal

[MD-LUCKY]

You're going to need to bear with me on the pictures.. I didn't put the clutch back together just to take a few pictures, but I think I can explain what you're looking at:



The small metal tab is at the very edge. You can actually see the stud that the tab bolts to directly above it. If I spun the clutch around to connect properly, that small metal tap would go over the stud on the flywheel.



Here is a better picture of the metal tab we are talking about. You can't make out the stud in this picture, but it gives an idea of how the floater plate is connected to the flywheel.



And this is the best picture I have showing both the metal tap and the stud on the flywheel. If you spun the floater plate around until that metal tab fit over the flywheel, you would be lined up. I tried pushing on the tab to see if it was a spring metal (thinking maybe that was how they helped seperate the floater plate from the clutches.) It has some movement. If I recall correctly, Haisley recommended that you adjust the floater plate form time to time with shims. I'm not sure if they still use this design or not.



Finally, this is just a full picture of the floater plate. You can just barely make out the taps on the sides.


This is a picture of one of the old clutches in the Haisley:



6cb, non-sprung hub, feramic material.

A look at the material:




This is the new clutch:





(I incorrectly said 3 grooves, it has 4 for the floater plate).

12cb, sprung hub, 3600 pound pressure plate.





So, which clutch shifts slower?


Neither. They shift exactly the same. Why? Because they function exactly the same. The clutch pedal travel distance is exactly the same, the throw distance on the transmission is exactly the same, the pedal pressure is a mute point, and the synchros are more than capable of handling the extra weight AND any bonds between the clutch disks and the floater plate or flywheel.

[TheNatural31]

I understand the reasoning.......YET....mine IS slower???

[Valair1]

MD your probably right, but both those are diaphram clutches, diaphram clutches do shift faster,they work quicker, less moving parts, lever type clutches have alot more moving parts, it makes them a little slower, also when we increase the clamp load on a lever type clutch we use a spring with larger wire size which decreases the amount of release.

[97singlecab]

When I had a 5-speed in my truck with the stock single disk clutch I could grab gears fast enough I could out run the sincros and grind going into every gear, it shifted very fast. When that wore out I put a 3600 6cb south bend clutch with a lever style pressure plate in. My truck became alot slower to shift, taking a half second or more between gears to engage especially the 2-3 shift. In racing I started to be outrun by trucks that were significantly slower than me. Even trucks I had previously outrun. So I'm pretty sure it wasn't all a placebo affect. Now also I have installed two of the 3600 12cb street dual disc clutches with diaphram pressure plates, both were in g56 transmissions. And both shifted very well and are alot faster than the clutch that was in my truck. Just my two cents from my experience.

[lmills]

I have ran both diaphragm style double disks and the lever style ones. The diaphragm was slick and fast. Both lever ones were noticeably slower hitting the gears.

[MD-LUCKY]

Originally Posted by Valair1

MD your probably right, but both those are diaphram clutches, diaphram clutches do shift faster,they work quicker, less moving parts, lever type clutches have alot more moving parts, it makes them a little slower, also when we increase the clamp load on a lever type clutch we use a spring with larger wire size which decreases the amount of release.

That is a factor I haven't considered.

My only concern with that theory is that both the diaphram and lever work in exactly the same way. IE: if they are both pushed in at the same time and speed, they should act in the same way.

I suppose, and this is completely guessing, a lever style could have more deflection in the metal preventing it from disengaging the clutch. You can't get as even a pressure on the lever style as the diaphram style, so it acts differently. Complete, 100% guess on my part.

[Tate]

Originally Posted by MD-LUCKY

That is a factor I haven't considered.

My only concern with that theory is that both the diaphram and lever work in exactly the same way. IE: if they are both pushed in at the same time and speed, they should act in the same way.

I suppose, and this is completely guessing, a lever style could have more deflection in the metal preventing it from disengaging the clutch. You can't get as even a pressure on the lever style as the diaphram style, so it acts differently. Complete, 100% guess on my part.

I've got two SBC DD's, one is a 3250 diaphragm style, sprung hub, 12cb. The other is a 3600 lever style, unsprung hub, 6cb. Which one shifts faster?

Answer: both shift exactly the same as stock.

As a lot of us know, that answer is incorrect. The 3600 shifts significantly slower, and has about twice as heavy of pedal as the stock and 3250, even though it only has 350lbs more clamping force. So even though the diaphragm and lever style plates are doing the same job, they are doing it dfferently which causes a heavier feel, and slower shifts. By rights, the 3600 should be the faster clutch, since it has half the friction material in contact. Plus since it is solid hub, should break and bonds faster, since there is no load up in the springs.

The haisley street drag you posted has tabs and spacers on the studs. I would be very curious as to the gap on an unloaded clutch disc and the floater plate on. Methinks this is why the Haisley's are known to shift faster, since the tabs are aiding in the release of the floater plate from the first clutch disc. The other thing about floaters like SBC that use 4 grooves is that the clearances between the floater and flywheel are quite tight. Get any heat build up and you get expansion. The floater plate has probably 20% of the mass of the flywheel, and will get twice the heat build up (due to two sides of the disc slipping on it vs. one side for the pressure plate and flywheel), you are going to get expansion. Take up the clearances, it will make it much harder for it to move.

[roachie]

X2.

[MD-LUCKY]

Originally Posted by Tate

I've got two SBC DD's, one is a 3250 diaphragm style, sprung hub, 12cb. The other is a 3600 lever style, unsprung hub, 6cb. Which one shifts faster?

Answer: both shift exactly the same as stock.

As a lot of us know, that answer is incorrect. The 3600 shifts significantly slower, and has about twice as heavy of pedal as the stock and 3250, even though it only has 350lbs more clamping force. So even though the diaphragm and lever style plates are doing the same job, they are doing it dfferently which causes a heavier feel, and slower shifts. By rights, the 3600 should be the faster clutch, since it has half the friction material in contact. Plus since it is solid hub, should break and bonds faster, since there is no load up in the springs.

The "heavier feel" isn't what is causing your slower shifts. What you're saying is that it takes more time to push 5.5 pounds of pressure down vs 5 pounds? The resistance levels are so minimal at those levels that it isn't a factor.. 5.5 pounds pushed 8" in 1 second is the same speed as 5 pounds pushed 8" in 1 second. We may notice an increase in pedal pressure, but that slight increase isn't enough to prevent an adult, especially an adult man, from pushing the clutch at the same speed as stock.. Unless you have serious muscle issues, you can push the pedal at the same speed.

The valid question here seems to be lever vs diaphragm. I can't make an educated comment on the lever system, since I have 0 experience with them. The only issue I can see would be deflection in the lever from the throwout bearing pressing against those 4 small forks at high speed. Pure speculation: if those forks move sideways as they move in, they may not fully release properly.. causing delayed shifts (would be the same as not depressing the clutch fully).

Originally Posted by Tate

The haisley street drag you posted has tabs and spacers on the studs. I would be very curious as to the gap on an unloaded clutch disc and the floater plate on. Methinks this is why the Haisley's are known to shift faster, since the tabs are aiding in the release of the floater plate from the first clutch disc. The other thing about floaters like SBC that use 4 grooves is that the clearances between the floater and flywheel are quite tight. Get any heat build up and you get expansion. The floater plate has probably 20% of the mass of the flywheel, and will get twice the heat build up (due to two sides of the disc slipping on it vs. one side for the pressure plate and flywheel), you are going to get expansion. Take up the clearances, it will make it much harder for it to move.

Clearance is a big issue, especially with heat. The Haisley was one grabby, nasty mofo when it was warm. The thing about the floater plate, when it comes to ANY of these clutches, is that it DOES have a major force against it. About 2800-3200RPM. Without the pressure plate pushing against the clutches and floater plate, that sucker is moving. The centrifugal force of 50 pounds at 3200RPM is more than enough to motivate things separate. In the most basic form, spin a paperclip on the end of your pen and see if it stays stationary.

I'm starting to wonder if folks are properly cleaning the splined input shaft on their transmissions when installing their clutch. That can also do weird things to shift speed. If you read through this thread, we are getting a huge range of "results." Some say the same, some say slower, and some say they even shift faster than the stockers. From a pure mechanical standpoint, there is no explanation why we would have that many different results with the same variables... Wish I had some actual speed measuring equipment. Time to call Time Warp and the Myth Busters!

[97singlecab]

I think fresh clean oil in the transmission has some effect on it. And is maybe made worse by the dual disk??? Does anyone have any time slips on a truck that has had both clutches in it? Mine got an auto in it before I ever hit the track with the dual disk, but I still can't agree with you MD-lucky. Mine for sure was slower.

[roachie]

Ok, I lubed the hell out of my input shaft. Still slow.

I think the diaphram style plate lift the actual pressure more evenly and have less leverage. The longer fulcrum gives them a quicker response but, they cant handle the higher plate load that a lever style can.

I never put any thought to the lever vs. diaphram style. Now that is brought up it does make sense.

[JasonCzerak]

What about motor retun to idle? I'm curious if the smarty can fix it so the motor fall back faster.

Has any one ever managed to get the motor to hang? specifically with a pressure box? It's easy to get a little past 3500 and it hangs there with the rail sky high. there is no getting things into gear at that point.

[ENafziger]

Hmmm, interesting thread.

In my '06, I've ran the stock clutch, a SB 3850 12 CB with the finger type pressure plate, and currently a SB 3250 12 CB with the diaphragm pressure plate. I've got the upgraded hydraulics as well.

With both SB DD clutches, I pretty much have to double clutch or shift pretty slow to get a good smooth shift. This was the case with the 3850 4 lever, and the 3250 diaphragm. For reverse, you've got to bump 5th, and then quick into reverse to get it to take. I've had the TSB done for reverse popping out of gear as well, and that made no difference. I've ran mopar and Amsoil ATF in the trans as well...again, no earth shattering difference.

The 3250 of course has a lighter feel, and maybe slightly quicker shifting, but really not that different from the 3850.

I don't think the issue is with increased inertia, or rotating mass. One reason I say this, is I added a Mitchell 2-speed gear splitter rated for 35,000 lb gvwr in a divorced configuration. This added significant spinning weight to the output shaft end of the transmission with no effect on shifting characteristics.

I think the real culprit is what Roachie and others have said...the floating plate and additional clutch just never fully separate. This makes sense if you think that we're packing two clutch discs into effectively the same space of the single OEM...there just isn't as much room to play with for full separation.

Here's another reason I agree with this. Having the 2-speed Mitchell gear box, I could select " Direct 1:1 -- Neutral -- 18.2% OD " When I put the gear splitter in neutral, and held the clutch all the way down, the stubshaft between the transfer case and gear splitter would slowly turn. The only explanation for this would be incomplete separation of the clutch discs creating enough friction to cause things to turn.

I can see where Haisley design could offer more complete disengaging of engine and transmission by more fully separating the discs...

Has any one ever managed to get the motor to hang? specifically with a pressure box? It's easy to get a little past 3500 and it hangs there with the rail sky high. there is no getting things into gear at that point.

Yep...when I crank the MP-8 over 40% or so and really hammer on it, the engine will hang for almost 2 seconds or so. On mine, it's all about being able to let off the throttle just before you're ready to shift to let the motor start coming down slightly on it's own before jamming the next gear at high rpm.

--Eric

[sb clutch]

Let me see if I can shed a little light. First off when it comes to high performance clutches there are obviously multiple ways to build them. The one question that clutch builders hate to hear is that I want to be able to street drive, drag race and sled pull. Well folks that's usually 3 different clutches. Look at it this way a guy calls me and is building a drag car i would build him a drag clutch cause he is using the car strictly for drag racing. With the diesel pickups most everyone wants to use it for all around purpose. Now actually there have been some very good points brought up with the weight of the disc, whether the center plate is strapped or not, whether the diaphragm pressure plate or lever style, single, double or triple disc. Even the amount of material on the clutch disc's. Here is something that we are finding very odd but seems to make sense. We have had multiple people take our double disc out and put a triple disc in and say that the transmission actually shifts faster. Here is our theory on that -- there is a fine line on the weight of the disc's on the input shaft from the single to triple. Obviously the single being the lightest and triple being heaviest. Is it possible that adding more weight will bring the input shaft to a stop sooner? Where as the double disc has justs enough added weight of rotating mass to keep the input ever so slightly dragging. The single is light enough to allow the transmission to stop quickly. I believe the diameter of the clutch also has a bearing on this issue. The larger the outside diameter the longer the disc will take to slow down. The smaller the outside the diameter the quicker it will slow down. When dealing with the straps on the center plate our original clutch design used them. i believe strapping the center plate will help it to find center and offer smoother shifting. When strapped what we found is that your only capable of allowing the center plate to move 50 thousands of an inch to free both disc's with the amount of travel that is offer by the hydraulics to achieve full release. If something were to warp via clutch disc or center plate due to heat the strap would not allow for any additional travel needed. When the center plate is not strapped and warping is involved it allows the center plate to find the center needed for release. As I spoke of smaller and bigger, lets say I build a 10 inch DD clutch with a diaphragm pressure plate and strapped center plate, this would definitely offer a quick shifting clutch pack. The problem is is how much will the clutch hold and how much heat will it take? Funny cars use 4 and 5 disc feramic clutches with lever style pressure plates and non strapped centerplates. Obviously they have assistance with the shifting that is different than your trucks. As clutch builders we have only so much room to work with. The clutch disc splines have to run on the input shaft and not run into the bearing retainer. This leaves us very little room to stack disc's. The bell housing only allows for only so much room for height of the pressure plate. We also, as clutch builders, want to take into consideration the protection of the transmission. Rigid clutch disc's will be lighter in weight but can ware input shafts, clutch disc splines and syncro's out in the transmission due to the diesel spikes. Properly built spring loaded disc's will help to avoid these problems. Now you have to put into the equation the shape of the main bearing in the engine and the quality of the transmission. These factors have a big part in clutch operation as I am sure you have seen with whomever clutch, that one will work perfectly in a particular vehicle and not as well in others. All this being said I promise that we will continue our research and development to improve the shifting of the performance clutches. Please take into consideration what we are up against. Huge horsepower and torque, heavy trucks with heavy transmissions designed to be work horses not dragsters and multiple uses for the same clutch out of the parameter of said design.

Peter

[JasonCzerak]

So Peter, what kinda clutches do you typically build to go into a road race car with full syncro trans and human shifted.?

[sb clutch]

On something like that a 3000 lb diaphragm single disc 6 button ceramic or feramic