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904 Clutch Plates?

Posted By: clonestocker

904 Clutch Plates? - 06/02/06 04:25 PM

Is there a difference in clutch material in the two different clutch packs? Taking my trans apart I have two different types of clutches? The guy at the parts store said it doesn't make a difference. I had Borg Warner in the high gear drum, and these black plates in the direct drum(?). These black plates are falling apart. Is it a problem to use the Borg Warner plates in both clutch packs? thx matt s
Posted By: 1100HPSmallBlock

Re: 904 Clutch Plates? - 06/02/06 04:49 PM

The forward (rear clutches) are thinner than the direct(front). If you swap them you have clearance issues.
Posted By: dartman366

Re: 904 Clutch Plates? - 06/02/06 04:52 PM

I don't believe it make's any diff on the material, but the thing that I have found is the grooves in the facing, one will have grooves straight across the face and the other will look like a waffle, the only other thing to watch is the thickness of the fiber plate, when I got my master overhaul kit from Mancini the fiber disc's were all the same blue plate material.
Posted By: dartman366

Re: 904 Clutch Plates? - 06/02/06 04:59 PM

Quote:

The forward (rear clutches) are thinner than the direct(front). If you swap them you have clearance issues.

that being the case then after reviewing a NAPA kit that I have, then the direct clutches are the waffle ones and yes there is a thickness difference, and the material appears to be the same in that kit also.
Posted By: clonestocker

Re: 904 Clutch Plates? - 06/02/06 05:20 PM

The waffle plates are .082 thick. The other plates are .062 thick. Using the .062 plates allows you to put 5 plates in the front drum. I was told to do this by Dave Smith @ ProTrans. Need more input. thx matt s
Posted By: John_Kunkel

Re: 904 Clutch Plates? - 06/02/06 08:47 PM

One reason for the difference in clutch material is because the rear clutch normally engages at idle with the car at a standstill and remains engaged for all forward gears, the front clutch engages under power.
Posted By: clonestocker

Re: 904 Clutch Plates? - 06/02/06 10:03 PM

John, Do you think it matters if the front drum clutches are in the rear drum also? thx matt s
Posted By: dizuster

Re: 904 Clutch Plates? - 06/03/06 12:04 AM

Oh I'm so glad I read this. . . do not put 5 clutch plates in the high gear drum without being very careful. Yes it works but there is a potential for a big problem there. The problem is that the input shaft/rear clutch drum splines do not engage the bottom (5th) clutch. I had one that I went round and round on trying to figure out why it would only flare the 2-3 shift at high rpm. It's because the bottom clutch wasn't engaged which caused it to keep the whole clutch pack from clamping. Now there are several different height rear drum splines, so if you have the right spline height on the drum you can do it, but I have not had good sucess. Search for my other post "everything you never wanted to know about a 904" There is a lot of detail about what I went through. . . Just my 2 cents, and maybe you already have the right rear drum spline, but just be careful!!
Posted By: dizuster

Re: 904 Clutch Plates? - 06/03/06 12:07 AM

By the way, I got my original brilliant idea from having a protrans apart from a pro nostalgia car. It seemed like a great idea, but they must make sure they use the correct drum.

Also supposidly because the direct drum is a dynamic apply, the waffle grooves cut in the clutches allow it to relieve the fluid between the plates. That's why the direct clutches are waffled and the rear clutches are not. The rear clutch is on in all forward gears so it never really gets a dynamic apply (unless you neutral slam it of course lol . . )
Posted By: DavidDean

Re: 904 Clutch Plates? - 06/03/06 02:13 AM

With the right parts as described above I used 5 clutches (thin) in the front drum with good sucess .But as stated above and in the 904 post you must have the right parts.I'm building a spare 904 and I've been back to the trans supply shops a number of times looking for the right parts LOL!
Posted By: John_Kunkel

Re: 904 Clutch Plates? - 06/03/06 09:11 PM

Quote:

John, Do you think it matters if the front drum clutches are in the rear drum also? thx matt s



The front discs usually have a waffle pattern to allow fluid to be squeezed from between the discs during engagement, the channels in the waffle pattern reduce the actual surface contact area but this is a necessary tradeoff for good application.

The rear clutches aren't applied under power and therefore don't need the waffle pattern so the reduction in surface area has no tradeoff benefit as it does in the front. A flat pattern with occasional diagonal slots and metallic lining is the traditional rear disc and offers the maximum surface area.

My , I'm sure some others will disagree.
Posted By: 440Jim

Re: 904 Clutch Plates? - 06/04/06 03:14 AM

I agree with John 100%. (or more)

And in the 904, it is more important than the 727 since everything is smaller.
Posted By: clonestocker

Re: 904 Clutch Plates? - 06/04/06 04:09 AM

Thanks John. matt
Posted By: ZIPPY

Re: 904 Clutch Plates? - 06/04/06 02:47 PM

Note: text from this thread has been added to "everything you never wanted to know about 904s" in an attempt to keep all the info together.
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