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Discussion Starter #1
I'm new to the forum realm, but I have this question. I recently fell into a set of Ford Racing 3.55 gears for very cheap! I started doing some homework on my car and found out that my 91 GT came with the optional 3.27 rear-end. Would it be worth my time and money to even make this gear change? The car is an AOD, running 255/55/16 tires.

Thanks...
 

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Trade the 3.55s in and get ya some 4.10s!!!! DON'T FEAR THE GEAR!!!!
 

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No, its not worth it. Go steeper like TRUUBLE suggested.... 3.73, 3.90, 4.10...
 

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I'd generally agree with going deeper than 3:55's, but it does
depend somewhat on your type of driving.

I went from 3:27's to 3:55's cuz I do lots of 80 mph freeway
driving, and it bumped it just a couple hundred rpm at that
speed, and put it in a real nice rpm range from 65 on up to
help with torque but without killing gas mileage (4,000 lb car,
warmed up 351). I'm currently running 245x45x17 with an
AOD, but working on a 4R70W swap with a little shorter OD
ratio then will go to taller 255x50x17 which will end up with
about the same hiway rpm.

Here's a calculator so you can see the effects of using
different gears.

AOD's have a fairly close gear ratio which means a fairly
high 1st gear, but they have a tall OD ratio so you can
still go deeper for a better launch without getting excessive
on the highway.

An AOD with 4:10's is about equal in overall 1st gear ratio
to a wider ratio 4R70W with only a little deeper than 3:55's
yet will have nearly the same overall OD ratio.



http://www.angelfire.com/fl/procrastination/rear.html
 

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I'd sell the 3.55's and get 3.73 or 4.10
 

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I have a 94 5.0, 5sp. with about every add on but , induction. I have 3.27's, 3.55's the best next. I do alot of highway, but 5th gear now has no A$&. 1-3rd are great, 4th is ok, forget OD. What can I do. Can I do a 5th gear change or should I do a ring and pinion chang? Thanks to all.
 

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What's happened with 5th? Is this all of a sudden? And I'm not aware if there's a gear ratio option for the T5 that you could do other than swapping most of the guts.
 

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I have a 94 5.0, 5sp. with about every add on but , induction. I have 3.27's, 3.55's the best next. I do alot of highway, but 5th gear now has no A$&. 1-3rd are great, 4th is ok, forget OD. What can I do. Can I do a 5th gear change or should I do a ring and pinion chang? Thanks to all.

Talk about reviving an old thread, this one is 2 years old..... :scratchchin

Eagleauto is right...what happened to 5th?

No you cannot change it out and besides that, it won't matter. I just went thru this with a 6 speed customer of ours. The 5th gear ratio isn't the only thing that determines the final drive ratio. It is a combination of the input shaft, countershaft AND the 5th gear ratio that determines the final drive.

In other words, your '94 model T5 has a .68 5th gear ratio. If you were to just change the gear to say a .50 gear, that doesn't mean the final ratio would be a .50. You would have to consider the tooth count on the input shaft, counter shaft AND the new .50 gear, to figure out the new ratio. I don't know off hand what your tooth count is on the T5 input and counter so I can't figure it out but in the case of my 6 speed customer who had a 6th gear of .62....he wanted to get a .50 final drive ratio. After doing the math, simply swapping a .50 6th gear into the same gear set(without swapping input and counter), the math came out to be a .60 final drive ratio.


Bottom line is it would be way cheaper and easier to play with the rear gear ratios verses changing out the internals of the T5. :bigthumbsup

For what it's worth, my daily driver is a 2000GT with 3.55's and a .67 5th gear ratio (T45). I am turning 2200rpm's at 70mph on 275-45-17 tires. I have plenty of umph to get up and go at that low rpm. :scratchchin

Richard
Tech Support
Tremec TKO, T45 & T56 Transmission Systems
 
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