questions about dual-diaphragm pressure plate

I asked this same question on "another forum", but I'm hoping to get more eyes looking at it for different ideas and approaches....

I installed a TIII dual-diaphragm PP in my car yesterday. For those that have done this I have a few questions. For those that are thinking about doing this, pay attention!!!

The first thing I noticed is that the pedal feel is ROCK HARD. There is NO indication whether the cltuch is disengaged at all(unless the car is running). There is no ramp up in the pressure and no platue...just HARD!

I want to know if that is normal?

The second thing I noticed was that it engages the clutch about an inch off the floorboard. There's really no pedal travel at all!

I want to know if that is normal also?

Now, I talked with my vendor and they said that people who get this thing usually end up welding on a peice of steel to the end of the clutch arm and drilling another hole about an inch away from the stock one, then they move where the cable is on the tranny to the other hole farther away from the pivot point to get better pedal feel. It sure would have been nice to know this when I got the thing. I don't have an issue doing it, I just would have liked to have had some fair warning. Yes, I understand there is a reason it says not reccomended for street use...it never gave the reason.

Does anybody have pictures of doing the above mod? If you have done it how did it effect the pedal feel and travel?

I'm figuring it will probably add about 1/4" to the travel and lighten the pedal marginally.


Any useful input on this would be appreciated. I can live with it, but I sure would like to make it a little better.

Oh, and I need to get rid of the stupid rubber bushing under the clutch cable retainer on the clutch arm. That thing is going to get destroyed! Plus I'm sure it doesn't help with pedal feel at all...

Anybody have pictures or a "how to" on that?

I seem to rememebr Iniviate telling me he did not like his, but I can't rememebr why. lol HTH!!!!

...kinda..LOL

Yeah That's all normal and why dual diaphram's suck. Imagine the pressure the thrust bearing is seeing. I have one sitting in a box in my closet if you want it. Just pay for shipping :)

What is sitting in a box? The pressure plate? LOL, I already have it in my car...don't need another one! hehe

Yeah, I already thought about the thrust bearing. That's why I spend as little time on the pedal as possible...I also am slightly concerned with the cable. I'm going to mod a release arm this week and hopefully that'll help out some.

I also got rid of the rubber bushing under the cable retainer. I am using a shoulder nut and a washer along with the stock metal retainer. So far it works really well. I can detail that if somebody wants me to...

You're just pointing out reasons not to run one of those POS style plates. Thrust bearing will be gone soon, possible clutch cable snapping, not to mention the huge force on your leg that it requires. Just slows down shifting speed too.

Well, I certainly hope the thrust bearing won't be gone soon. I need this car!

All these things I wish I would have known BEFORE I got it, but there was NO info out there. It's listed as an "upgrade". Well, it WILL hold more power for sure.

I was going to get a plate from a different ventor, but I was told by them that their plates could not be used with other people's clutches due to some sort of thickness varience. To me this sounds like a load of BS. Why would you make it so a pressure plate can't be used with different clutches? Better yet, why would you sell a clutch that can't be used with other PP's? If you want to be proprietary fine, but if this truly is the case, then you just limited your market and possible income. I for one want nothing to do with either a disk or a PP that can't be used with other standard parts that are out there. Hence the reason I went with this PP...and am kind of regretting it now.

Here is my experience with a dual diaphragm pressure plate: The TIII unit may be the best stock pressure plate but it is way too stiff with 2 diaphragms. The one I'm using is made from a Luk TI pp and it works GREAT. It's not so stiff that it gives you leg cramps and it holds 375 ft. lbs. of torque without a problem. It does release close to the floor but that is actually a good thing because it minimizes the time that you're not transmitting power and it softens the engagement for less drivetrain shock.

Your pedal stops may have to be modified to give you a longer throw. The lower release point of the DD plate may require more throw than you have, especially if you make the clutch arm longer.

I still use the rubber cushion on the end of the cable and have never had one crap out. One thing I recommend is to grease the cable and the bushings on the throwout shaft to reduce pedal effort and cable strain.

I use a stock style organic disc and I couldn't imagine anything working any better.

The bushings are already greased. :thumb: When I got rid of the rubber bushing on the clutch arm I gained moe pedal feel and it also made it so the realease point is higher up in the travel...no more inch off the floor! :amen:

I've got another clutch arm with me that I'm going to modify. I don't honestly think I'm going to run out of travel room with the small increase in length of the arm(I only need about 1&1/2" total travel for complete engagement now). If it ends up that I do have to do more mods I can throw my stock arm back on until I can do the other things.

Seeing as this has been done before with success I don't think I'll have an issue though.

I do want to point out that the cable on my car was replaced just before I bought it about a year ago. So at least I'm not dealing with a 20 year old cable! YAY!!!

I do agree that I beleive an intermediate DD PP using twin TI diapgragms would be a good compromise between the stock TIII and this thing. :thumb:

I wanted to update this thread.

I modified a clutch arm I had laying around by adding 1.125" in length to it. I also moved the cable to the outer hole on the tranny boss. The result? MUCH better pedal effort! It is a tad heavier than what the stock clutch was in this car(keep in mind it was fairly heavy to begin with). I can actually bear to drive it in traffic now!

The lengthened arm along with eliminating the rubber isolator between the arm and the cable stay make a WORLD of difference! I beleive that the DDPP should be sold WITH a modified clutch arm as I think it would result in a lot more happy customers with the product. If not this, than at LEAST state that this mod is HIGHLY reccomended on the product page!

Thanks to all that contributed...I hope this helps others in the future...

update us when your thrust bearing takes a dump.

Hmmm...wow, thanks for the positive outlook.. :/:confused:

Quote:

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Originally Posted by GLHNSLHT2

update us when your thrust bearing takes a dump.

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Have you even run the DD plate yourself? If not that shut your freakin hole.

I had no problems with mine at all, on a daily driver. Ran a ceramic/organic disk with the DD plate. No clutch cable snapping issues, no problem with the TOB, and no problem with the pedal engagement.
The pedal was VERY stiff for about 1000-2000 miles, after that it loosened up quite a bit.