I already did somewhere, but I’ll explain it again. It’s simple really.
You can take any transmission and apply this to it, but because 300 foot pounds is the number in this thread, we can use that.
It doesn’t take much to make 300 ft/lbs does it? Let’s take a 273 2V engine. I don’t know what it made for torque, but I could look it up. If it’s 300 that’s all it is. That’s only 1.099 foot pounds per cubic inch. Pretty anemic.
So let’s drop in that 300 ft/lb gear box and let’s leave the 7 inch, rock hard pizza cutter tires on it. There is no way you’d ever break that gear box with that combination. Long before the gear box broke, youd smoke the tires.
Along that same line, we drop a 408 in there and it’s now making 500 TQ. That’s what? A 66.6% increase in torque. It’s the same thing. Long before the gear box breaks, the tires smoke like a chimney. So how does a torque rating make any sense?
Throw some bite on the 300 TQ combination and unless you can turn the tires it will break the gear box. Now add in a parts breaking clutch and you just made it worse by an order of magnitude.
Along the same lines, we can follow it up with a different example.
I have no clue what an A833 is torque rated for because I’ve never seen a number published. For the sake of the argument I’m sure it’s at least as strong a TKO60 which is rated at 600 TQ.
Let’s take a 340, making an honest 450 torque in a 2800 pound car. The A833 should be more than strong enough. So should the TKO60 box.
That same 405 TQ, 2800 pound car has a set of 14-32’s on it and let’s say a Ram 3 puck clutch. It’s highly unlikely that will spin those big steam rollers, especially in 3rd gear down the track. 3rd gear is the weakest gear in the transmission.
You bang 3rd and crap 3rd gear so fast you can’t get the clutch back in. Was the gear box rated too high, or did a big tire and a parts breaking clutch kill it?
I’ve seen guys miss on their clutch tune up and break Top Loaders and about every brand you can think of. I’ve seen one Liberty get hurt, but that was low gear. I’ve seen a couple of GForce G101’s get killed by engines that were nowhere near the torque rating.
My point is that torque is a piss poor way to rate a gear box. It’s basis is in marketing not in fact. It’s a simple way for the manufacturers to establish some arbitrary number to scale so the average guy can think he has a way to compare transmissions.
It’s like comparing cylinder heads by CFM and totally ignoring port size and shape.
Transmission torque ratings mean very little. Buying a transmission based on a torque rating is like buying a cam based solely on seat to seat timing. It ignores the big picture.
Simple as that. Make the tires spin and you can run a very low rated gear box. Put some bite to it, add a lock up clutch in front of it and then drop the hammer on it and you can’t buy a good enough transmission.
