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Discussion Starter · #1 ·
Picked up a rigid direct drum band last night in Kevlar for $65.
Thought that was a pretty good price considering they are hard enough to find lined with even stock lining.
Will be interesting to see if it makes any improvement in the 2/3 shift.
 

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I've used a couple of them i got in the U.S and IMO the shifts are similar.I think it's more of a preference thing. They are nice and strong but then in my own i had a choice and i used a kevlar flex.
 

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Discussion Starter · #3 ·
I was thinking along the lines that due to the nature of the rigid band, it "should" release easier/quicker than the flex, with less drag.
Yes, definitely much stronger than the flex..
 

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I'm running a ridgid kevlar band in my trans right now. It is slipping. I haven't tried to adjust it yet. Running an "H" servo. Last week at the track it was slipping going into second.

I read on the monster thread that ridgid bands need a bit of run-in time to get seated. I have always run a flex band in the past and had fair luck. I don't know if I'm sold on this ridgid band yet. Maybe it will get better.

I also read somewhere that kevlar linings don't have as high of fiction. The high performance paper lined bands should hold better. I don't know if this is true. The kevlar is mostly benifitial in that it takes heat better and therefore last longer.
Does anyone know if this is true?

_________________
Grabber Green '70 Mach I 351C 4V 12.32 at 111mph
Robin Egg Blue '79 Fairmont 408C 4V 10.50 at 127mph

<font size=-1>[ This Message was edited by: clevelandstyle on 8/20/06 6:58am ]</font>
 

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Yes, the rigid band is thought to be a bit stronger ( I have seen one break in a stock tranny). They are made of cast iron - I think the steel bands are stronger but I don't know that the difference is a big deal because the aluminum case is weaker than either of the two metals in the bands - Cast iron is just a bit more brittle than the Aluminum or steel.
The problem with the rigid band is that it is rigid. It doesn't conform to the drum which is round. It takes time to wear in the band to fit the drum as well as the flex band fits immediately. For racing purposes the flex band is your best tool for the job. For the street - if you have lots of patience you can wear it in so that it will work as well as the flex band will right away. I don't use the rigid bands even if a customer wants one I will try to talk him out of it! As for the coefficient of friction of Kevlar it is lower than the normal or even high performance linings. The standard street linings have a higher coefficient of friction than a lot of the heavy duty linings - they just have higher heat tollerance. The kevlars heat tollerance is high enough that the drum will over heat before the band retains enough heat to fail. To me, that is not a good thing - it is easier to replace a band than it is to replace the drums and a darn sight less expensive too. The high performance "paper" friction material is the best thing to use for the extreme use transmissions (over 600 HP) but I have found that Borg Warner plates will easily handle 400 Hp engines when the tranny is prepped for the abuse.
Personal preference and my experience. Your milage may vary. The only band I have seen broken was a cast band - I have seel steel bands blue from heat but not broken. I have just been lucky I suppose.
Paul
 

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Discussion Starter · #6 ·
I have never broken a flex band either but the racing career has only been one (mixed) season. I have read of others tearing the flex band ears off though and one of my cores had a band in it that had done exactly that....so maybe there is something in that.
Sounds like I may have made an error of judgement here regarding the kevlar. I mainly tried to track down the rigid band as I see them appearing in most aftermarket build HD trans'....perhaps the HD kick is more geared to towing and the like, rather than what we are trying to do.
However I will give it a try..... I now have a switch arrangement set up on the shift lever and an LM-1 doing the data logging (crude but works)....so will now be able to see exactly when the shift is initiated and how long the trans actually takes to complete the changes and any flaring. I have had this working in the past and can easily "see" and measure the time it takes to shift, but the switch will add alittle more definition to the whole setup.
Talking of band material, how does the carbon/kevlar mix stack up as far as "grip" is concerned??
 

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I don't know how the carbon/kevlar stacks up as far as coefficient of friction. I know the carbon/kevlar brake pads work well, even with water spray on them but in oil? That is where the "paper" really shines it will grip even through the oil. Is there anyone, besides the racers, who actually experiment with these materials under actual working conditions? Can we get a hold of their information? I'm thinking I may have to start drilling oil relief holes in the bands - or groove the drums diagonally for the high torque trannies. anyone in the Seattle area want to be a guinny-pig? Maybe installing relined "snap bands" with different friction surfaces to see what locks up better - that way you can change them in the car, you wouldn't even have to pull the tranny.
 

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FWIW - I've got 1600 passes on a flexible Kevlar TCI band.
 

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On 2006-08-23 05:35, PaulS1950 wrote:
Maybe installing relined "snap bands" with different friction surfaces to see what locks up better - that way you can change them in the car, you wouldn't even have to pull the tranny.
I understand that snap bands are easier to change, but I don't feel they are strong enough. I have seen many of them break in mild applications.
 

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I run a C4 into the 9's with a kevlar rigid band and cant really see why you would want to use a flex band.
 

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Discussion Starter · #11 ·
I thought I would do a search on the web regarding the kevlar friction ratings and found a manufacturer of brake and trans linings. This is taken from there site -

Approximate Wet Friction Properties
- in automatic transmission fluid (after extended burnish)
Wear rate: 1/2 to 1/5 that of organics and paper, 1/2 to 1/3 that of sintered bronze materials
Dynamic coefficient of friction: 0.10 to 0.15 µ in the 23 - 290 W/sq. cm range (0.2 - 2.5 HP/sq. in.). Approximately 10% higher than paper, maintaining coefficient beyond the energy limits of sintered bronze
Static to dynamic ratio: 1.05 - 1.15


Kind of "put the brakes" on what is said here regarding the "grip" factor of kevlar
 

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Discussion Starter · #12 ·
The rigid band showed up today, nice piece and definitely much stronger looking than a flex band.

I got to work comparing it with a glide band....whilst that band is slightly larger diameter the C4 is wider. The actual surface area is quite close between the two, with just over 1sq" advantage to the glide.....but even an R apply piston is slightly larger than the glides apply piston....so the actual clamping force is probably near identical !!!
Further to that, the glides drum is larger but is considerably heavier than the C4 drum, so as far as inertia and a spinning drum are concerned, the advantage must go to the C4....hhmmm
 
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