You obviously have never saw a case crack on a C-4, I have, The cast pans DO add a significant amount of strength. Think of the pan as a girdle for the trans. But i will say to each his own, if you don't want the expense,and dont have the power or the traction it may not be worthwhile to you.
I have seen C4 cases crack, at the servo cover and the adjusting studs and the tail housing from exploded governors. I have never seen one crack through the pan area. It is reinforced by all the casting (more than two inches of it) for the valve body mounting and passages and the valve body itself reinforces it. Cast pans are between 3/16 and 1/4 inch thick and compared to the amount of aluminum in the case they are no thicker and they are made from a weaker alloy. As I said a cast pan adds little to the strength of the C4 case. It's weakest points are the adjusting studs and the metal around them. The intermediate servo covers will break if you push pressures too high and the cases will break at the adjusting studs for the same reason. Keep pressures right and things hang together real well. As for experience I have built C4's for over 1000 HP engines and I have only seen one C4 case failure that wasn't associated with the intermediate band. It was behind the pan and was a result of a disintegrating one way clutch. The pan and the case supporting it was fine. It was a deep stamped steel pan - not cast aluminum. Thirty-five years working on these little trannies and almost as long building them for racing has shown me what and where I need to reinforce for performance uses. If you have had different experiences then I would suggest that you do what is necessary to prevent those things from happening when you build your transmissions. I will continue to do the same in the way I have been building them.
Blown 5.0, We used to put a one to two inch steel spacer between the case and the pan on the C6's. Now THOSE break cases easily with high torque use. There is a big difference between a 1/4 inch of cast aluminum and a steel band 3/4" wide by 2" high all the way around the pan mount. With 1500 ft lbs. and close to 1800 HP The C6 was doing all it could to stay together - even with the girdle of steel. The C4 is so compact that it will handle 1000 HP (probably close to 800 ft lbs.) without any girdle unless you are running a 3-400 shot of nitrous. The 302 is more likely to split than the C4 though in that kind of application. I used to like building the C4 for 429's and 460's but I don't do much of that any more - most of my builds now are for resto-rods and street and strip cars. Nothing much over 600 hp.
Steel and cast aluminum have different expansion rates when heated, This may have contributed to your breaking problem. I to have been building and racing C-4 for 30+ years. Not to mention my partner actually has made his living for the past 40+ years building and repairing transmissions. The cast pans stop the case from flexing, Anytime you close up a big gap with somthing rigid you will improve your chances of the part survival. I usually don't comment on many threads just the ones i have had true life experiences with. And like i said to each his own, I'm not downing you, it was you that flamed my orignal comment. I would have had no other reason to comment on your message other than that. There will be no further comments from me on this topic.
Never broke a case with a two inch girdle on it. I replaced a few that had cast pans with no girdles that were broken, and never had any trouble with them after adding girdles (new cases of course). In my experience C4's don't have the same problems, at least up to 1000 hp. Your experience may be different. That is why I said to keep doing what you feel you need to. I didn't intend any flaming. I have only been working on transmissions since 1971. I started building racing trannies in 1974 or 75... Been a while. Now retired and building trannies for friends. Have a great day.
