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I seek the sage advice of my fellow forum dwellers. I plan to put a T5 in my '67 and was about to go pick up a new gear set for the 9" rear that's about to go in. It dawned on me that I honestly don't know what ratio would be ideal for such a set up. It's a locking rear with 3.00 at the moment (and disc brakes! w00t!) though I was thinking somewhere between 3.50 to 3.73.

I believe the tranny I'd be installing specs out to [email protected] and [email protected] - but again, this doesn't necessarily mean I fully understand what numerical combinations are practical.

Suggestions / pros n' cons ?
 

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what do you plan to use the car for?? if it was mine id go with the 373s. i mean it has overdrive, so thats not too big of an issue. hell my car runs at about 2750 rpm on the freeway. 2 extra gears would really be nice
 

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In short, a daily driver with decent freeway m.p.g. *but* still be able to light it up from stoplight to stoplight. Not that I would.. well.. you know what I mean.
 

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OD

Repub,
I have 3.73's in my 69 XR7 with a C6 and 9" trac lok. Smokes em effortlessly in 1st, chirps going into second. If the OD 5th gear is really .63 then your options are pretty good. I cruise at 3000rpm at around 62 mph. But with the 5spd you could probably go up to 4.11 and still be OK. You may want to ask the AOD guys what gears they run, as I believe the OD on those trannies is about the same or less.
Paul Garvin
http://home.sprynet.com/~pamar/cougar.html
 

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With my AOD I'm running 3:73's and that makes a great combo but my cam would like 4:11's better. If you do a lot of highway driving I would recommend the 3:50's or 3:73's depending on how big your cam is. You also want to consider tire diameter, I'm running 275/60/15's which is a pretty tall tire.
John
 

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Think of it this way...

The 'normal' T-5 behind a GT Mustang is coupled with about the same tire size we're running in our Cougars, Yes? GT Mustangs came with 3.08s, 3.27s or 3.45s. If their 302s can get those cars to move, our more potent Cats surely can!

I used to have a T-Bird Turbo Coupe. The T-5 in those cars had a lower first gear than the V-8 T-5. Even the poor little 2.3 liter in the Turbo Coupe only had 3.45s with a stick. It did quite nicely, too. Especially when you consider it was only a four-banger! It had 235/60/15s or 225/70/15s on it (stock size was 225/60/15).

Heck, even my 89 Grand Marquis with its AOD came with the 'higher' gear ratio of 3.08s (standard was 2.73s!) The trailer tow rear gears were (well, that's what I have in there now :D ) are 3.55s. I can smoke 'em in first and get a good 10 foot long 'chirp' going into second.

Now, what conclusions did you come up with after I laid it all out for you? I'd go no higher than 3.50 or 3.70s if you want to retain any sort of gas mileage. If you really don't care, go as far as 4.11s.
 

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If the od 5th gear is indeed .63-1 a set of 3.73's would give a 2.35 final drive ratio in 5th gear if I remembered how to figure this correctly. .63 X 3.73 = Final drive. .63 x 4.11 = 2.59 FD. Just something to think about.

Someone correct me if I am doing it wrong, my middle aged brain is clogged sometimes. mm
 
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