soundguy said:
I think you should check your math. 1st on the T56 matches the 3650 with a 3.73 gear. The rest are all improved in terms of torque multiplication through the drive line.
I agree that any conversion to a T56 requires a rear gear upgrade to match the low gear performance of the 3650. What you are not accounting for is the tremendous improvement in "staying on the torque/HP curve" which the T56 produces. Especially in an engine like the Cobra 4.6 where dropping down below the peak can adversely affect performance. The 1-2 shift on the 3650 produces a big torque/HP dropoff compared to the T56.
Using a 4.10 will produce an additional improvement across all gears compared to the 3650 (16-25%) and that's why it makes sense. In addition, the T56 will produce 6th gear (.62 vs. .67) results with the 4.10's similar to what the 3650 can do with 3.73's.
Finally, the enormous increase in ruggedness locks it for the T56. The small amount of additional weight will more than balance against the increase in reliability and efficient use of the Cobra's power production characteristics.
Otherl, broader torque curve motors may benefit less from the T56's advantages, but the ruggedness still remains.
You do point out some things I hadn't thought about, but I don't agree with everything you say. I still think that the T56 with 4.10s gives less torque multiplication in first than the T3650 with 3.27s (see below).
Maybe you're talking about the Cobra "R" T56. It has shorter gearing than the rest of the T56s, but how many Cobra "R" transmissions are there floating around? Are people putting the Cobra "R" transmission in their GTs? Maybe so. But even that T56 falls well short of the T3650 in first gear (2.97:1 vs. 3.38:1).
Every source I have shows '03 Cobra T56 ratios of:
2.66, 1.78, 1.30, 1.00, .8, .63
Every source I have shows T3650 ratios of:
3.38, 2.00, 1.32, 1.00, .62
If you put 4.10s behind the T56, you will have overall ratios of:
10.91, 7.30, 5.33, 4.10, 3.28, 2.58
If you put 3.27s behind the T3650, you will have overall ratios of:
11.05, 6.54, 4.32, 3.27, 2.03
As I stated before, the T3650 has a shorter first and a longer overdrive, which (in both cases) is exactly what you want.
It is true that after first gear, 4.10s behind a T56 give more torque multiplication than a T3650 with 3.27s. Most people run their T3650 with 4.10s, though, giving ratios of:
13.86, 8.20, 5.41, 4.10, 2.542
To get the same first-gear ratio from an '03 Cobra T56, you'd have to put in a set of 5.21:1 rear-end gears. Even with the Cobra "R" T56, you'd need 4.67:1 rear-end gears. I don't see many of those sizes! Besides, once you jack the rear-end ratio up too high, you start running into gearset (and housing) durability problems.
As far as keeping the car in the torque curve goes, think about a hypothetical 1/4mile race betwen two identical cars, one with the '03 Cobra T56 and another with the T3650. Assume they both have 4.10s. In my experience, the cars will use gear 1 through 4, and in all four gears the T3650 car will get more torque multiplication, except in fourth where it's a tie. In first, the T3650 car will use 13.86 vs. 10.91 for the T56 car. Second gear, the T3650 gets 8.20 vs. 7.30. Third gear it's 5.41 vs. 5.33. Fourth gear, it's 4.10 for both cars. The T3650 car will win this race every time.
If you give the T56 car in the above example the Cobra "R" transmission, it will have overall ratios of 12.177, 8.487, 5.863. and 4.10. The T3650 still has a big (1.683:1) advantage in first. The T56 gets a slight advantage in 2nd and 3rd (.287:1 and .453:1), and it's a tie in fourth. So even assuming you can get your hands on the Cobra "R" transmission, and put 4.10s behind it, it still doesn't necessarily beat the T3650 with 4.10s.
In fact, I'd still bet on the T3650 in that situation. Realize that the first gear ratio is the most important in the 1/4mile, for a simple (but often overlooked) reason: a higher overall ratio in first will allow you to leave the line at a higher RPM without spinning the wheels. Most people agree that launching with good RPM, and without spinning, is the key to racing the GT.
And what about a hypothetical 1/4mile drag race between a stock (3.27 rear) T3650 car and an otherwise-identical car with the '03 Cobra T56 and 4.10s? The T3650 driver only has to shift twice, vs. three times for the T56. You can count on some lost time there... I'd guess at least 0.3sec, probably more. Plus you have to consider that the T3650 will have more multiplication in first. Yes, the T56 will have more in 2nd and 3rd, but while the T56 driver is shifting into 4th (4.10 overall), the T3650 driver will have the gas floored and will be winding out third (4.32 overall)! I am pretty sure the T3650 car will win this one as well.
I haven't even touched on parasitic loss, weight, etc., all of which work against the T3650. Also, some people race the 1/8th mile, where the T3650's shorter first gear will help even more
All of this is posted to point out that Ford knew what they were doing when they were sorting out the '99+ driveline. Most people would never think that a GT with 3.27s could hang with (much less beat) a GT with an '03 Cobra transmission and 4.10s.
