Dual Disc clutch owners, any problems shifting over 5,500 RPMs?

[biomedtechguy]

I know a number of forum members have dual disc clutch and pressure plate setups. Because of the heat that slipping a clutch hard, at the launch, using a HitMaster launch/clutch controller, McLeod recommended the RXT model, which I have broken in and have no problems with. The material makes it a bit "grabby" in that it's not as smooth as an organic disc, but I'd roast an organic clutch and the smell of burning hair isn't pleasant. The 572 RB is going to be in front of it once it's done, but for now, my 440 6bbl will provide the power.
So I let the 440 6bbl wind out to 6k every time I'm WFO, not "forced", but it wants to. Rev limiter set at 6,200.
Anyway, I'm asking this question because I haven't had ANY problems shifting at 6k RPMs, but someone with a lot of manual transmission experience said that "dual disc clutch systems don't shift that well over 5,500 RPMs."
I know that over 5,500 RPMs isn't a common territory for many big blocks, but if any of you have a dual disc clutch system and shift 6k RPMs or higher, please share your experience.
Thanks.

 

[Sascha]

No problems past 6k.
470, A833, McLeod Twin Disk

 

[Derwud]

Single disc on mine, but I can bet it is a improperly setup.. Clutch arm throw may be causing issues.. Have seen it on a few cars aftermarket and OEM.

 

[biomedtechguy]

Single disc on mine, but I can bet it is a improperly setup.. Clutch arm throw may be causing issues.. Have seen it on a few cars aftermarket and OEM.

Thanks. I have an American Powertrain hydraulic throwout bearing setup. Hydraulic throwout bearing is required to use the HitMaster clutch release controller.
As I posted, I'm not having any problems shifting at 6k RPMs, or at all.
Because the person who told me this has a lot of professional experience with manual transmissions, I posted this thread like a "poll".
It struck me as counterintuitive that dual disc clutch systems could be "inherently" difficult to get a good shift over 5,500 RPMs since they're designed for racing.

 

[INTMD8]

So far my McLeod RST (organic discs) shifts great at 7500.

Had their organic twin disc in a high 9 second 4th gen F-body, worked great.

Sold my twin turbo 07 Z06 to a friend, shifts great with an RPS triple carbon clutch and 1400 rwhp.

Could keep going but no, should not be an issue shifting a multi disc clutch at high rpm.

 

[biomedtechguy]

Well, I thought his statement was odd.
Anyway, thanks for confirming what my experience has been: no shifting problems, including over 5,500 RPMs.
Now to overcome the challenge of making time to go run my car.

 

[padam]

My guess is they have that reputation due to the increased mass of the disks.
I believe that causes a delay in synchronization between shifts. Maybe more of an issue when downshifting as in road racing?
Just guessing.

 

[INTMD8]

^ Possible but you have to calculate polar moment of inertia not just overall weight as most multi disc clutch discs are substantially smaller diameter than a single and unsprung.

 

[65Fury440]

I have an A855 trans and the same clutch setup, shift 6800-7000 depending on if tires slip at all in 1st and 2nd.
Powershifting might be a whole different story though.

 

[INTMD8]

^ Forgot to mention I regularly powershifted my high 9sec turbo camaro. It would go from 145 to 149 trap speeds if my right foot never left the floor.

 

[biomedtechguy]

So far my McLeod RST (organic discs) shifts great at 7500.
Had their organic twin disc in a high 9 second 4th gen F-body, worked great.
I regularly powershifted my high 9sec turbo camaro.

Great info!

Powershifting might be a whole different story though.

Thanks!
Since I got my FBO ignition system with the rev limiter, at least 5 years ago, I have ALWAYS done "no lift shift", but pop that clutch pedal to shift. With the 6bbl, it is especially beneficial to keep the gas matted, to keep the outboard carbs open.
ZERO problems with the dual disc, power shifting, at 6k to 6,100...
NOW, admittedly I have not been to the track in WAY too long, especially given the HUGE investment I've made in parts and labor, but work life and "wife life" that damn construction project in Mississippi that after a 3 year long NIGHTMARE has had its final final inspection and passed, so now anything that my wife wants me to do...well, sometimes it's going to have to wait, or I'm not doing it AT ALL.
Yeah, all work was making this "Jack" more than dull, miserable, borderline psychotic, angry almost all the time...
It's not even my work or my business that was doing it, it was the "ZERO time for anything I wanted to do" to the point of not even thinking about "what would I like to do?" because that would just rub it in my face how AWFUL things had become.
Rant over.
Soon, very soon, it's time for some outings, just me and the Roadrunner!

 

[65Fury440]

I'm with you on needing car time. I'll just go drive mine when I want some stress relief. It bothers me when it's not together running.
As far as no lift shifts, I don't have the cajones to do it.
Will the 855 take it? Will the tires break loose? Will it throw rods out the bottom?
It's not worth it to me to find out for a half second better ET.
Again, with the 500ish hp motor I did it all the time. With the new roller motor there is a lot more power being transmitted.
But in a dedicated drag car it sure is fun to watch!

 

[biomedtechguy]

My FBO ignition system's rev limiter has performed reliably and flawlessly.
Although the FBO ignition system is "solid" and far from an "average upgrade", it has a very simple but brilliant mechanical total advance limiter built in, so I can have my at idle timing advanced higher than stock (about 20° BTDC). THAT has been reported by MANY 6bbl guys as being a crucial factor in smoothing out the idle and an overall contribution to better performance, and I agree. It has a tunable vacuum advance can and the curve can be adjusted as well. The FBO module uses the factory ECU box wiring harness and connector, so that's easy, and it comes w/a jumper to bypass the ballast resistor, but it can appear stock. The rev limiter is very easy to set, absolutely flawless in performance and reliability. It's a true multiple spark output unit, and unlike "other" so called multi spark units, this one continues to produce multiple sparks in the higher RPM range.
Having said all that, the vacuum pod adjustment is something that I haven't been able to do, despite trying several Allen wrenches larger, smaller, and exactly the size Don at FBO said to use.
I'd have to either look up or ask Don at FBO how to make any adjustments to the settings on the system.
So while I have enjoyed it, I am happy to say that the Progression Ignition system that literally is a concept in action that I've always dreamed us "carb guys" could have is the next step for me, and I am going to use it in my 440 6bbl, but I am extra enthusiastic about it's work it will do in my 572. Of course, it has a rev limiter. I may need an outboard 2 step, to be able to mat the gas at the starting line w/out overrevving my engine, but I have to discuss that with Progression, that's one question I don't think I've asked them yet.

 

[dvw]

Depends on how fast you can shift. Are you Ronnie Sox or grandma? A higher mass clutch will always shift slower. Properly built (still using synchros) 833 with a single disc will shift with full throttle by just tapping the clutch to get it to release. Try that with a newer shift rail trans and dual disc.
Doug