6spd vs 5spd

That one (2.66/1.78/1.30/1.00/0.74/0.50) is the Viper type, which has a 6th gear ratio ok for an 8 liter V10 but tough for a mustang...
The T56 of 03 cobras has following ratios: 2.97/2.07/1.43/1.1/0.8/0.62

That one (2.66/1.78/1.30/1.00/0.74/0.50) is the Viper type, which has a 6th gear ratio ok for an 8 liter V10 but tough for a mustang...
The T56 of 03 cobras has following ratios: 2.97/2.07/1.43/1.1/0.8/0.62

Just a note reguarding the 6 gear in the T56 with the stock 3.55's the RPMs are higher in 6th than my GT with the 3650 was in 5th at the same speed. The gears are alot closer together which is good for racing but general driving can get tiresome. When driving normally I usually go 1st, 2nd, 4th, 6th

I like my 6-speed.

What RPM's are you GT drivers at in 5th gear doing, say.....65, 70, 75?

vipergts281 said:

I like my 6-speed.

What RPM's are you GT drivers at in 5th gear doing, say.....65, 70, 75?

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2337 for 65 to 2697 for 75 based off calculations @ http://www.tchracing.com/tech/gearcalc.php w/ 4.10s.

downsouthman1 said:

2337 for 65 to 2697 for 75 based off calculations @ http://www.tchracing.com/tech/gearcalc.php w/ 4.10s.

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Thanks. But I meant with stock gears....I should of mentioned that. I'll just use the link you posted, thanks.

No problem. I guess it should've been inherent that you meant stock gears. My bad.

Stock gears was something like 70 or 75 @ 2000 rpms.

But the stock gears sucked.

I used to go about 2200 RPMS in 5th @ about 78mph. The chart @ the website should show something similar.

GinoGT said:

Stock gears was something like 70 or 75 @ 2000 rpms.

But the stock gears sucked.

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Hah, I bet 3.27's do suck. 4.10's are much better in a GT. As for me, I'll be sticking with my stock 3.55's. Traction is already bad as it is.

It's kinda cool w/ 4.10s. I mean I don't really all to well know yet since I'm still breaking-in the clutch but 2nd I can romp & hold trac for the most part & 3rd will hold good. 1st I won't mention as far as holding quality.

downsouthman1 said:

It's kinda cool w/ 4.10s. I mean I don't really all to well know yet since I'm still breaking-in the clutch but 2nd I can romp & hold trac for the most part & 3rd will hold good. 1st I won't mention as far as holding quality.

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Well that's good. You must have some sticky tires.

If I get on it, I don't grip until 3rd. It's a good and a bad problem to have.

I somewhat understand. I compared gears 1-5 on my tranny to same gears on your tranny & it's basically identical. But I need 4.10s to attain what you have & be off less than 5mph w/ any same gear & any same RPMs. But YOU STILL have another gear, & that's the beauty of the T-56 Cobra Tranny.

downsouthman1 said:

I somewhat understand. I compared gears 1-5 on my tranny to same gears on your tranny & it's basically identical. But I need 4.10s to attain what you have & be off less than 5mph w/ any same gear & any same RPMs. But YOU STILL have another gear, & that's the beauty of the T-56 Cobra Tranny.

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Yeah, I need that extra gear with the way I drive. I usually speed. So the rpm's are high even in 6th.

Ok, I think a few things need cleared up about transmissions and gears, because it seems that a lot of you don't understand. The idea of a gear train is to trade of speed for torque or vise versa. Gear something down you can get more torque, but you lose speed. When it comes to motors/engines gears help to convert the engines speed from 6000 rpm and 300 lb*ft of torque to something more useful for propeling a car. 300 lb*ft of torque is not enough to make a 3500 lbs car accelerate at any usuable rate. Also, if you turned the rear wheels at 6000 rpm you would be doing 40,841 ft per minute (6.8 ft per rev) or 7.73 miles per minute (5,280 ft per mile) which is 464 mph. So, first gear in a trans is to trade off speed for torque. OD is basically used to trade off torque for speed.

When it comes to the number of gears in a trans the number of gears and the actual ratios that are picked depend on the application. If 1st gear can give you a lot of off the line acceleration and OD can give you top speed, then you can use gears in between to give you different levels of acceleration or speed to bridge the gap. Every time that you use a gear there is some range that the engine's rpm is going to overlap into the range of the next gear's. 6000 rpm in 1st is, for instance, 1000 rpm in OD. The more gears that you add the more each gear's rpm range overlaps the next gear's. The idea is to select the number of gears and their ratio so that the gear's rpm bands overlap so that the engine is always in its power band. For example, the 4.6L like to make its most power in n/a "stockish" form from 3500 to 5500 rpm. You want to select the number of gears and their ratios so that through your whole race that you can always select a gear to stay in this rpm range to maximize performance. Less gears mean that you will have to go out of the engine's power band. The trade off of having more gears is that you have to shift more often. The closer the rpm ranges the more peak power you can uses.

Averaging the power of the gears is the baest way to see this. With only 3 spds you power usage would look like 3 peaks overlapped where there is a large space between the peaks. As you added more gears the peaks become closer together, and the average power used goes up. See picture.



The engine's power band has a lot to do with how many gears you have. Engine's with "peaky" power bands require trans with more gears to keep the car inteh power band. Themore power you make through out the rpm band the less important the number of gears that you have. Yes, I know the new cobra comes with a 6 speed. That is however due to the fact that the car is designed for road racing where being in the peak of teh power band is very important. Also, I think a lot of it has to do with the "coolness" factor.

The rear end gear basically scales all the ratios up and down by the same amount, and is used to give you more overall top speed or more off the line accel.

Well put slider. Thanks for clearing up some of the ?s I didn't ask. I understood half of the concept. Now I understand more. I do have a ? related to another subject. Your sig says you have a SPEC Stage 2 clutch. How many miles did you break it in?

The 03 Cobra also has a T56 because of it's (UNDERRATED) 390HP/390TQ, and the fact that SVT/Ford knows the cars will be beat on, as well as modified. Modification in this case being significant, since a smalley pulley and a great tuner can get the car way into the 400's RWHP.

A T3650 probably wouldn't put up with that kind of abuse for any extended period of time. Plus the fact that those cars are also going to see plenty of duty as daily drivers, Ford wouldn't enjoy repairing busted input shafts and blown synchros (or whatever the heck it is would go wrong) on their $$$.

Coolman532 said:

I was just thinking. What would happen to a car that came with a 6spd standard and switched it to a 5spd. For example switching the 03 cobra trans to a 5spd. Not that i would want to do this. But i am just wondering is it possible. How would it effect the performance.

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Who knows. For the most part, it's just about what the ratios are. Ratios better suited to the car, better performance. Bad ratios, bad performance.

True that's why 4.10s work so well w/ a NA T-45.