And yet another "your uncle is wrong" only for different reasons. He was close when he said the tranny will amplify hp, the gearing will actually amplify torque, the ability to lift something heavy with your pulleys. Think about a little four cylinder truck pulling a boat, it can do it just fine in the low gears where torque is amplified but loses out when you have to shift up. Where your uncle got it wrong is with the hp part, since hp takes time into account it doesn't matter how easy it is to "lift" your heavy weight. Using his example: if you tie a rope through a set of pulleys and lift up your engine block it will look like you are very strong but to determine your hp you have to factor in that it took you much longer to lift the engine than you could have if you didn't have all the pulleys. So if your equation for one pulley looked like HP=X/Y where X= the weight lifted and Y= the time it took, then when you put in the set of pulleys the equation might look something like this HP=10*X/10*Y. You see you are lifting much more weight but since it took longer the end result is the same.
His argument using different rpm is also completely bogus because all engine will make different amounts of power at different rpm, you would have to use the same rpm in each gear. If you did that you would find that first gear would lift a lot of weight slowly and 5th would lift a little weight very quickly. This is due to torque multiplication through the gearing. I'm sorry to hear that your uncle is so misinformed, it's people like him that give mechanics a bad rap because they just know how to fix a given problem and not actually understand what they are doing.
His argument using different rpm is also completely bogus because all engine will make different amounts of power at different rpm, you would have to use the same rpm in each gear. If you did that you would find that first gear would lift a lot of weight slowly and 5th would lift a little weight very quickly. This is due to torque multiplication through the gearing. I'm sorry to hear that your uncle is so misinformed, it's people like him that give mechanics a bad rap because they just know how to fix a given problem and not actually understand what they are doing.