question about change to 6-speed tranny

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Scotter - 15 Jun 2006 14:13 GMT

I have a 96 GT Vert with stock tranny except some work about 4 years ago on
differential so asked them to put in 3.73 gears.

Now, with gas being so expensive, I'm much more aware of the fact that at
70mph my RPMs in 5th gear are kinda high! I think around 2400 but not sure.

So... I could go back to 3.23 or 3.27 or whatever they were stock OR it
would be really nice to keep that 1st gear the way it is for quick launches
and add a 6th gear for highway driving. I realize you can't just "add a 6th
gear". I mean buying whatever it takes to have something that resembles my
current 3.73 setup but has one more gear past 5. Is this possible or close
to possible? How expensive a process? Is there an online retailer anyone
recommends for the parts?

Thanks!

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Scotter
96 GT vert
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Michael Johnson, PE - 15 Jun 2006 22:17 GMT

> I have a 96 GT Vert with stock tranny except some work about 4 years ago on
> differential so asked them to put in 3.73 gears.
[quoted text clipped - 9 lines]
> to possible? How expensive a process? Is there an online retailer anyone
> recommends for the parts?

I have a T-56 six speed tranny in my '89 LX and can tell you it is a
nice addition. However it is not a cheap modification and installation
isn't just a simple bolt-in procedure. By the time you are finished it
will cost you around $3,000-$3,500 which would buy a lot of gas. IMO,
the 3.27 gear is a good compromise for highway cruising and good
acceleration with a 5-speed. Don't swap to a T-56 thinking you will
save much on gas. The economics don't work in your favor.

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My Names Nobody - 15 Jun 2006 23:59 GMT

>> I have a 96 GT Vert with stock tranny except some work about 4 years ago
>> on differential so asked them to put in 3.73 gears.
[quoted text clipped - 18 lines]
> a 5-speed. Don't swap to a T-56 thinking you will save much on gas. The
> economics don't work in your favor.

Besides, is there much difference in their final top gear overdrive ratio?
I think the overdriven top gear engine RPM would be nearly identical between
the two, no?

After all it wouldn't be like replacing an old Allison transmission with a
new double overdrive one would it?

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Big Al - 16 Jun 2006 01:01 GMT

> >> I have a 96 GT Vert with stock tranny except some work about 4 years ago
> >> on differential so asked them to put in 3.73 gears.
[quoted text clipped - 25 lines]
> After all it wouldn't be like replacing an old Allison transmission with a
> new double overdrive one would it?

The six speed is .5 to 1 in sixth. Fifth is about the same as fifth in a
five speed.

Al

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Michael Johnson, PE - 16 Jun 2006 02:24 GMT

>>>> I have a 96 GT Vert with stock tranny except some work about 4 years
> ago
[quoted text clipped - 35 lines]
> The six speed is .5 to 1 in sixth. Fifth is about the same as fifth in a
> five speed.

I think the ratios in mine is 1:1 in fourth, 0.8:1 in 5th and 0.62:1 in
sixth. The 5th gear in a T-5 is extremely tall for a 5-speed at 0.67:1
so there isn't much drop in rpm at highway speeds when going from a T-5
to a T-56. One gear I found extremely useful for some reason is 5th
gear in the T-56. It is great for cruising in steep areas or roads
where the going speed is varying around 45-60 mph. Plus it gives a
better top end than 5th in a T-5.

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Big Al - 16 Jun 2006 07:00 GMT

> >>>> I have a 96 GT Vert with stock tranny except some work about 4 years
> > ago
[quoted text clipped - 43 lines]
> where the going speed is varying around 45-60 mph. Plus it gives a
> better top end than 5th in a T-5.

Here are the ratios for a stock 94 to 2002 Z28 T-56:

Gear ratios:
2.66:1 first, 1.78:1 second, 1.30:1 third, 1.00:1 fourth, .74:1 fifth, .50:1
sixth, and 3.28:1 reverse.
Torque capacity: 450 lb-ft.

Here are the 93 ratios:

Gear Ratios: First 2.97:1, Second 2.07:1, Third 1.43:1, Forth 1.00:1, Fifth
0.80:1, Sixth 0.62:1, Reverse 3.28:1
Design Torque Rating: 400 lb-ft

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.boB - 16 Jun 2006 00:57 GMT

> I have a 96 GT Vert with stock tranny except some work about 4 years ago on
> differential so asked them to put in 3.73 gears.
[quoted text clipped - 11 lines]
>
> Thanks!

The stock Ford T56 is a nice trans with 2 OD gears (.80 and .62), and a 2.66
1st. It's plenty strong enough for most near stock applications. It is a fairly
simple bolt in job, with no real fabrication. It has an integrated bellhousing.
The T5 you have now has a .68 OD, and a 3.35 1st. If you swapped, you would
gain almost nothing on the top end, and you would lose a lot at the bottom.
Performance would be very disappointing for all the work and expense. Not worth it
IMO.
Your best bet is to go back to the stock gearing. But that may not be cost
effective. You'll have to find out what the cost of a gear change is, guestimate
mileage improvement, and then figure out how many miles it would take to break even.
You may find it's best to just keep what you have.

http://www.fortesparts.com/catalog.cfm?catalogID=2

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.boB
Arrived: 2006 FXDI, Red.
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2001 Dodge Dakota QC 5.9/4x4/3.92
1966 Mustang Coupe - Daily Driver
1965 FFR Cobra - 427W EFI, Damn Fast.

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Michael Johnson, PE - 16 Jun 2006 02:26 GMT

>> I have a 96 GT Vert with stock tranny except some work about 4 years
>> ago on differential so asked them to put in 3.73 gears.
[quoted text clipped - 28 lines]
>
> http://www.fortesparts.com/catalog.cfm?catalogID=2

I forgot about using a T-56 from a Cobra. It just might bolt in
relatively easy. For a Fox body there is a lot of welding needed and
the stock (and several after market) H-pipe will no longer fit around
the bigger T-56.

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Big Al - 16 Jun 2006 07:00 GMT

> > I have a 96 GT Vert with stock tranny except some work about 4 years ago on
> > differential so asked them to put in 3.73 gears.
[quoted text clipped - 25 lines]
>
> http://www.fortesparts.com/catalog.cfm?catalogID=2

Or just buy a complete stock rear axle out of a wrecking yard.

Al

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Backyard Mechanic - 16 Jun 2006 01:56 GMT

> I have a 96 GT Vert with stock tranny except some work about 4 years
> ago on differential so asked them to put in 3.73 gears.
[quoted text clipped - 12 lines]
>
> Thanks!

New Wheels, taller tires. win-win

Signature

Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!

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Scotter - 16 Jun 2006 14:26 GMT

Wow thanks for all the great advice!

So... and forgive the ignorance...

Buying a stock rear axle from a junkyard would be like switching out the
differential? It all tends to be together? Maybe if I decide to swap out the
headers for the 2000+ so that my hp goes up a bit, going back down from my
3.73 gears won't feel like a performance hit and then I'll have the ?taller?
5th gear again so I can cruise 75-80 on road trips at relatively low RPM and
still have good oomph off the line and in low gears.

Signature

Scotter
96 GT vert
3.73 gears
K&N Filtercharger

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>I have a 96 GT Vert with stock tranny except some work about 4 years ago on
>differential so asked them to put in 3.73 gears.
[quoted text clipped - 12 lines]
>
> Thanks!

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