Th400, 2:73 rear end torque converter input

[chaosrob]

I have a mildly warm Pontiac 455 with a RAIV Cam @ ~ 450 hp. The car has a TH400 and a 12 bolt 2:73 posi rear, 28" tires and weighs 3600#'s. The car will see a lot of mixed highway/city use and is just a driver car, will most likely never see the track. At some point down the road I will most likely be throwing a gear vendor behind the th400. I do not currently have any interest in installing a 2004r or 4l80 in the car, I like the th400.

I have not driven the car yet with the current setup and it still retains the factory torque converter, which I am sure will be a bit of a bore with that rear gear ratio. I am looking for input from the experts here about a recommended converter setup that will be fun, street manageable and not create heat generating issues while driving. I know the consensus will most likley be to change the rear gear setup but it is not something I want to do.

Input from those in the know is much appreciated, TIA

[Vimes]

The only thing I will suggest is adding an aux trans cooler right now, that is between the trans output side and the radiator. This will remove excess heat, then running it back through the engine cooler will make sure the fluid going back to the trans is the same temp at all times as transmissions do not like fluid temp changes, and do not like it either too hot or too cold. Putting the cooler after the radiator can result in the fluid being too cold in the winter.

After you drive it with the current setup you should have a better idea of what you want to do with it. Your engine should have the torque to carry through with the TH400 and 2.73s, but a stall converter in a TH400 is going to be a heat/mileage killer and not ideal for a daily that never sees the track. The issue is a TH400 can't do torque converter lockup (that I am aware of) and without a locking converter you're always going to see slippage at cruise.

When you are open to a trans/rear gear swap, you'll get better results. A 4L80 can handle a locking converter, and the overdrive will allow 3.23s for better acceleration while retaining mileage with the overdrive and locking converter. The 200-4R or 700-R4 would be strong enough to live behind 450HP without robbing as much power to spin itself.