Alternate (Better?) Ways to Up the Direct Clutch Friction Count
You saw me use the ALTO thinner plate setup to raise the friction count from the stock max of 6 to 8. I expressed my thoughts on the heat that was going to produce and the thermal mass being smaller.... and cautioned to add a larger cooler.
Some well respected builders use this setup and swear by it. Others hate it and swear at it, claiming it burns up. So... how can you UP the count using stock frictions?
Well, there are two ways. First off.... remove the top pressure plate (last in)... and in it's place if it put one more friction and one more steel. Top that steel with the thinnest retaining snap ring FORD makes (P/N F3AZ-7D483A - .052 in thick - although you may be able to get proper clearance using other thicknesses, maybe) and you now have a 7 plate direct clutch. Relax, the thinner steel will do just fine in place of the thicker pressure plate. Oh, the P/N for the most current production friction plates is F8AZ-7B164-BA. They are black with radial grooves, not the waffle pattern any longer. These plates are supposed to be virtually indestructable.
Next, if you have access to a lathe, or a machine shop... take the piston out of the direct clutch and strip it down to bare. On the side facing up into the clutch, machine off .100 of material from that face. (Not any proprietary secret, just what it takes to get the clearance.) Then build it like we just did the 7 plate version, but this time, you will have room for 8 stock plates.
Cheaper than ALTO, and with fewer drawbacks. More difficult for the average Joe.
While we are here, let's talk about clearances in clutch packs. FORD specs are quoted in this article where they apply. General rule of thumb is that .005' is the close side per friction disc (eg. a 5 plate clutch would be tight at .025") and .010 is high (eg. a 5 plate clutch would be .050").
Jerry W. suggests when in doubt err on the high side - s'why I suggested the thinnest snap ring in the stock 7 plate setup - your results may vary, measure. The Snap rings for this drum are P/N F3AZ-7D483 A thru D.... 4 thicknesses A, B, C and D.
4R70W Rebuild Diary - Part 5 - Direct drum | Ford Explorer and Ranger Forums - Serious Explorations