I am in the process of building my transmission for a 600 HP P-Pump motor for my 91
It is all documented here:
http://real-man-truckworks-and-survival ... ic=458.225
Thing is very little is coming out within the proper clearances.
History: I went to RevMax and told them I needed the parts to build a transmission to hold 700 HP. $4200 later in parts, I began to upgrade the A518. It has every good, better or billet part made and a great low stall converter along with a billet flywheel and even ARP flywheel bolts, a deep pan and a way bigger trans cooler.
Following the RevMax guidance I installed the extra clutches in the OD section and darn if the clearances are way more than they allow. Same thing happened with the low/reverse clutch pack. The only one that came out right was the direct clutch pack at .038 with the called for clearances being .025 to .045"
Here's the weird part, the direct clutch had 4 clutches and 4 steels factory. RevMax supplied a much thinner (.086") pressure plate and 6 clutches and 6 steels. SO when I put the 6 + 6 into the drum, there was no room for a reaction plate! None!
But by just finishing with a steel and placing the wavy snap ring in the groove, I came out with the .038" which is good to go.
Can I run that clutch pack without a reaction plate?
Next, when I pulled apart the low/reverse clutch pack and removed the factory piston it did NOT have an inner seal! Nada...nothing. I used a new billet piston and fitted a new flanged seal in there, but it was a holy terror fitting it.
When I built up the next assembly, the one with the sun shell and my pretty new billet shaft and measured that clearance, it came in at .050" The manual says the max is .048" so that is out as well.
I'll say, anyone thinking of building their trans themselves, you are in for a ride! It is not easy!