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Bored at work today, so I've been messing with gear ratios. I think I've come across an attractive alternative for N/A Cobras. It has to do with the '03 version of the T-56. Let me know if I'm really on to something or, if not, what I'm missing. Here goes.

I think this transmission would make an excellent choice for N/A (STREET-TIRED or DR) '96 -'01 Cobras with very steep rear gears (ie. 4.56/4.88). Here's why.

I really like my car with 4.10s. However, I do wish first was not quite so low. Looking at the ratios, with a 4.56 and the '03 6-Speed, first would be an overall 12.13 ratio which is measurably less than my T-45 with a 4.10 (13.82). This would help with traction problems, increase speed in first, and because speed is higher before shifting to second, it would also reduce the RPM drop to second gear (even with the higher 1.78 second, the overall ratios are almost identical at 8.12 for the t-56/4.56 versus 8.16 for the T-45/4.10).

So far, we've got a more useable 1st gear and smaller RPM drop to 2nd gear. Both positives.

Moving on, the advantages just seem to get better. Third in the new T-56 is very similar to 3rd in the T-45 and 4th is idenical at 1:1 in both. Therefore, we can gain usability in 1st, keep 2nd virtually unchanged, and yet get substantial leverage benefits of a 4.56 or lower gear in both 3rd and 4th :joy: :joy: :joy:

What am I missing here? Sounds to good to be true. And yes, I do realize the 4.56 would be much steeper for highway cruising. However, even this is better in the '03 T-56 (.63 OD 6th versus .67 OD 5th). Actually, the highway RPM for such a combination would be nearly identical to a 4.30 geared T-45 which is entirely liveable (2.87 versus 2.88 overall ratios).

So, where would the downside be, other than expense?
 

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I've done the same numbers crunching, and come to the same conclusions. Then... I discovered (from some early reports not yet proved...to be fair) the 03 trans is not the same hi strength trans as the normal T56 for modulars. We'll find out soon enough.
 

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Discussion Starter #3
Thanks for the confirmation Ralph. I can certainly understand your concern for ultimate power handling ability with the RWHP you're putting out!

For me, though, I doubt I'll ever mod to anything more then 300 or so RWHP. In the next several years, I'll be focusing more on suspension and weight reduction stuff (assuming I ever bite the bullit and stop using the Cobra as my daily driver!) With my intended purpose and power level, I doubt I'd be able to break an '03 T-56, especially since my T-45 shows no signs of wearing out. I do, however, want a plan for when it does go, and I think the '03 T-56/4.56 combo will be a "contenda"!
 

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T-56= T-45 with less 1st gear, and an extra gear between 4 and 5.

I am not a big fan of the t-56 tranny gear ratio's. I mean, how often do you really need a .8 overdrive gear? Most people don't realy worry about the drop from 4-5 in the t-45 cause they don't race in it, for those that do it's a great tranny, but because most of us don't, couldn't somebody design a tranny with closer ratio to take advantage of the fact that we have a 6th gear now. I do think that the t-56 is a very smooth shifting tranny, and it is very strong.
 

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I had decided recently to go ahead and put the 2.97 first gear T56 in my car...then I got to thinking about the costs VS the alternatives. A new T56 plus mounting kit, new driveshaft, shift kit, and "knob" would be at least $3000. D&D sell T45's for $995. I can buy three T45's for the price of a T56. Just something to think about. A road racer would probably enjoy the T56. Drag racing is still mostly about traction and maybe HP. As long as it stays together, the T45 is OK for drag racing. (and I'm aware of the ratio oddities) MHO
 

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Then... I discovered (from some early reports not yet proved...to be fair) the 03 trans is not the same hi strength trans as the normal T56 for modulars.
Surely to heaven Ford has learned it's lesson on that. I'd be really disappointed to find out that's true, especially given that by all early accounts the engine is most likely under-rated.
 

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clearwaterms said:
T-56= T-45 with less 1st gear, and an extra gear between 4 and 5.

I am not a big fan of the t-56 tranny gear ratio's. I mean, how often do you really need a .8 overdrive gear? Most people don't realy worry about the drop from 4-5 in the t-45 cause they don't race in it, for those that do it's a great tranny, but because most of us don't, couldn't somebody design a tranny with closer ratio to take advantage of the fact that we have a 6th gear now. I do think that the t-56 is a very smooth shifting tranny, and it is very strong.
Actually the .80 is what I like best. I like to take my car down semi-twisty back roads at like 50 mph. With 4.30s the thing is too buzzy in 4th but bogging in 5th. .80 would be great for my drving style and use of the car. Then again when my new motor is done I very well may de-gear!
 

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Jerry,

Boredom and work must go together:D I did the same thing a couple of weeks ago and reach the same conclusion, the T-56 and 4.56 gears look like a great combo. But if I were able to convince "She Who Must Be Obeyed" that I need a new tranny then I would be stuck in CP with you and still losing to the FS guys:eek:
 

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The T-56 and 4.56's ARE a great combo! :D
 

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How about instead of a new tranny, just getting re-geared? Anyone know of a kit or shop that can regear a t-45, if it can even be done? What kind of cost?

If you go with the T-56, the only way to go right is with the Viper T-56 with .50 6th, that' makes all the difference for highway driving. I love my 4.10's but I'm always stopping myself from looking for another gear on the highway with my T-45...

Lon
 

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Discussion Starter #12
Re: Hmmm...

91TrackSHO said:


I have an excellent excel spreadsheet that allows variables such as tire size and specific ratios and RPM for any 5 & 6 speed with any rear end combination (mustang or not). You can input the ratios (or your own numbers if you like) and compute speed in each gear at any RPM. This is truly telling the higher you modify. Email me your address and I'll be happy to send it.
I'd like to have a copy! Please send it to [email protected] whenever you have the time. Thanks
 

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Discussion Starter #13
KyCobra said:
Jerry,

But if I were able to convince "She Who Must Be Obeyed" that I need a new tranny then I would be stuck in CP with you and still losing to the FS guys:eek:
There's this saying I've heard before, goes something like its easier to beg forgiveness than get permission! Now I wouldn't practice something like that :D but others might.

See you at Commonwealth, hope it doesn't rain!
 

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Re: Hmmm...

91TrackSHO said:
I have an excellent excel spreadsheet... and I'll be happy to send it.
Please e-mail it to me too. Thank you.
[email protected]
 

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Thanks for the e-mail 91TrackSHO! :) Pretty neat! :)
 
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