FMX extra clutch plates?

FMX extra clutch plates?

Joined: October 4th, 2011, 12:15 pm

July 27th, 2012, 10:37 am #1

Hello there everyone!

I´d like to beef up my FMX trannies (I've got several from -68 to -72 of them, all from passenger cars) and it seems to be that no one offers any heavy duty or such components for this trans any more. So what can I do nowadays to make it withstand serious abuse or at least some healthy torque and hp figures? I'm thinking of putting one behind a blown 351C for example...

(I've got four C6 boxes too, but since they eat up power so much, I'd like to go with the FMX instead. A friend of mine swapped a C6 in place of his FMX in a -68 Galaxie 390, and his ET in 1/4-mile got one second worse! Is it possible that C6 robs that much more than FMX?)

I'll use a Trans-Go shift kit of course, but what else is there in the market?

I've got one converter (from a -68 302 car) which has been modified to +800 rpm stall speed above original, but I don't know what the original stall was.

I'm kinda new in rebuilding trannies, but I understand that putting some extra clutch plates will strenghten the trans. So can I put extra plates in the existing cylinder/drum and how is that done? Or do I have to try to find cylinders/drums from a version which already has more plates? And if so, what version should I be looking for?

And I live in Finland, Scandinavia, Northern Europe, so finding these parts, new or used, ain't as easy as it is in the USA... and getting them here from the States ain't cheap either!

Thanks for any help!

Reg's,
Jari
Last edited by JVN-63 on July 27th, 2012, 10:41 am, edited 1 time in total.
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truck doctor
truck doctor

July 27th, 2012, 10:34 pm #2

up until last year i used the fmx exclusively for drag racing . 4500 stall boss hog convertor with a shift kit, fuly auto tweeked to shift at 6500rpms. it ran great with the exception of the intermidiat band .we had to reinforce the actuator end as it was distorting. clutch plates you can eliminate the bellveld washer and you may have room for a added clutch.you may need a thiner snap ring. this is all depending on the stack hight.these are tough trany's. we swapped to a c4 combo witch by the way pars are a plenty, 4500 convertor same hp same gear lowered the et by .500 thats on half seconds.i personaly like the fmx because all the guts come out the back.no need to remove the trany for overhaul.eather way maintenance is key and refreshing the trany is important if your using it for drag racing. good luck
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Joined: October 4th, 2011, 12:15 pm

July 28th, 2012, 11:32 am #3

By "bellveld washer" do You mean the "waved cushion ring" as it's called in the shop manual, if I remember right?
I don't recall any other washer-looking parts in the clutches.
And that's only the rear pack, what about the front pack, there aren't any washers to discard,
or anything else for that matter, to make room for the extra clutch plates (friction and metal), is there?

How much clearance should there be at the minimum between the clutch stack and the snap ring in the rear clutch?
And should there be an equal clearance between the input shaft and the snap ring in the front clutch pack?

Where can I get the thinner snap rings if needed? I believe I can't find them here in Finland...

And thanks for posting!
-Jari
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Joined: November 18th, 2004, 4:20 am

July 28th, 2012, 2:08 pm #4

Yes the wavy cushion spring in the direct drum can be eliminated.
The pressure plate can be shaved to enable another clutch plate.

Rule thumb clearance is .010 - .012 per fiber plate, so for a 4 fibre pack anywhere from .040 - .048 clearance on both packs.

You can try measuring various plates to get a good clearance if no snap rings are available.


The FMX is one strong muddah transmission.
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Joined: October 4th, 2011, 12:15 pm

July 30th, 2012, 8:34 am #5

Thanks Stu!
With this information I get pretty much going on!

I have torn apart two of my FMX's, a -70 unit and a -72 unit. Both have 5 friction plates in front pack and 4 in rear pack. What was a bit surprise to me was that in the -72 unit's front stack there was one steel plate thicker than others. It has been a while since I checked it, but I imagine it was about 0.02" thicker. So far I haven't seen anyone mentioning anything about different steel plate thicknesses, so can someone explain this thing to me?

Anyway, next I should try to put 6 friction plates in the front clutch and 5 in the rear clutch, right?

By the way, are the friction plates different materialwise in front vs rear clutch, I know they are not of same thickness but are they otherways interchangeable? It could be useful when seeking for proper clearances.

-Jari-
Last edited by JVN-63 on July 30th, 2012, 11:51 am, edited 1 time in total.
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truck doctor
truck doctor

July 30th, 2012, 10:14 pm #6

5 frictions in the front clutch is fine. if you can get 5 in the rear or high clutch is what you want. get rid of your wavy spring and alternate steel and frictions and you will have to figure out what presure plate and snap-ring combo to use.to get 40-50 th gap. you could use 2 or 3 steels in the place of the thick presure plate. or get the thick plate machined down to get that gap. the only week link is the band anchor point on the band . i put a 1/4 bolt across the open end and tack the bolt on the end to stifen the band end.i found that extrem power shifting the center point of the band anchor would bend and the band would go out of adjustment. this is only on flex band ,if you have a solid band you are good to go.
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Joined: October 4th, 2011, 12:15 pm

July 31st, 2012, 12:41 am #7

The -70 unit had a solid band in it, too bad the friction material was totally gone... Relining it, well I don't know who, where and how, and if it could be done, what kind of material is that compound? And how thick was it in the solid band originally?

By the way, is there a solvent or something that could be used for cleaning old but still good and usable band linings and friction plates? Not talking 'bout hi-po rebuilding now... =))
Last edited by JVN-63 on July 31st, 2012, 1:11 am, edited 1 time in total.
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Joined: November 18th, 2004, 4:20 am

July 31st, 2012, 4:24 am #8

Any form of solvent will work.
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Joined: July 17th, 2011, 7:07 pm

July 31st, 2012, 4:13 pm #9


Do NOT use water based solvent!

The water soaks into the friction material and then when the trans is put into use, the heat from normal operation makes the water steam, and it will blow the friction material right off the steel backing.

This is why a trans that get antifreeze or water in it from a radiator cooler leak, will cause the friction material to "peel" off the steel backing plate.

 
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Joined: October 4th, 2011, 12:15 pm

August 1st, 2012, 6:54 am #10

I only asked because in the -72 Ford Shop Manual it's told not to use any type of detergent solution when cleaning bands and friction plates, instead one should only "wipe them off with a lint-free cloth". I wasn't quite sure what "detergent solution" meant in finnish, but I guess they are all water-based, as dish-washing liquids etc. So for example lacquer thinners (xylen, toluen, acetone) are OK?
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