904 Trani
Any idea how much I can mill off the pressure plate of the read drum? 0.125????
I have never seen anything written in stone but my personal feelings are not to take more than .050" off. That pressure plate needs to be plenty thick to withstand the pressures it endures or it'll bend and fail. As I mentioned earlier in post #3 there are different thicknesses of snap rings that hold the clutch/steel stack in place. That's the first place you look to gain or reduce clutch plate clearance. It's possible your carrier has the thickest selective snap ring in it now which is .085" thick. The thinnest snap ring measures .061" thick so just by using it you can gain .024" of clearance.
I also wouldn't worry one bit about using a 3 clutch rear clutch carrier for a 350 hp application if I were using upgraded frictions like you are. Set the clearance to .030~.040 and you'll be fine
www.wittrans.com is a great place to buy good used parts reasonably. Look up your transmission and click on the drum you need and a page will pop up showing all the available drums for it. I just looked and they show 4 and 5 clutch carriers but let me warn you not to use a 5 clutch carrier unless you also use a rear drum that's made to accept 5 clutches. A 5 clutch carrier will appear to go together but in reality the bottom disc will not engage onto the splines so it won't work
Also keep this in mind. Your parts supplier sent you all thin clutch discs so that means if you get a 4 clutch carrier it's going to take 5 clutch discs and 5 steels to take up the extra space left because of using thin discs in a carrier designed for thicker discs. Even then you may have to have the pressure plate milled down some to get the proper clearance. I just rebuilt a 904 and converted the front carrier to 5 discs/steels by using thin discs and had to have .030 milled off the pressure plate to get the proper clearance
BTW: earlier you said all the clutch discs they sent measure the same. What was that measurement? I'm assuming right about .061" thick but it's good to verify