Originally Posted by 0trbo4myCHEVUICK
looking into going 3.73 but its whatever came from the factory in there now im sure. Its a 1982 chevy c10 silverado. im not looking for advice on what engine or trans too choose. I already have a buick 231 3.8l v6 in the truck, and im about to put a TH400 behind it. Just wondering what gear/stall ratio is going to be best to help the motor out. Or if maybe there is an upgrade for the 400 that makes it less draggy. I guess im asking if anyone knows where to find factory torque curves for this motor..
Use a stock TC if the engine is stock. 1800-2000 rpm is plenty. A lower rear gear will help but it will also run up the cruise rpm on the highway so be prepared for that or use a gear in the 3.4-3.5:1 range and split the difference. A lot depends on how you use this truck- as a DD or as a work truck, etc.
But until you know what gear is in it now, this is guesswork. You can check the RPO code
sticker (often in the glove box) and see what the ratio was originally in it- it's likely the same as when it was new.
More on checking the gear ratio here