would it be a stupid idea to put an aod behind a 300? I have the offy dp, headman header, and holley 390. My gear is 3.08. I know that it allready needs the 3.55 as is. I am just curious if the automatic tranny would suck all of the power.

 

A modern auto doesn't really suck that much more power than a standard, probably only 5-7 hp. This is more than made up for by a good torque converter because it acts as another stage of gear reduction and torque multipliation when it is stalled. A typical stock converter will multiply torque by about 2.5 when it is operating near its stall speed. A really good aftermarket converter can multiply it by 6 or 7 times.

With the AOD there are a few items to watch out for. The first is the way the converter locks up. It doesn't use a clutch inside the converter like most autos do. Instead, it uses a two piece input shaft that connects the converter housing directly to the direct drive clutch effectively eliminating any converter slippage in 3rd or 4th gear. This isn't too big a deal except if you are pulling a hill and need a little more than your engine can give. In that case the converter can't just unlock and give you more pull, the only option is a down shift.

The other weakness of the automatic is heat. They have a natural tendency to generate a ton of heat that you have to get rid of. This is easily overcome by a cooler, but that can create it's own problems.

Have you considered an E4OD with an aftermarket controller? It's a much better trans than the AOD and will take a lot more beating before it dies.