question about change to 6-speed tranny

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!

Reply to
Scotter
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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.

Reply to
Michael Johnson, PE

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?

Reply to
My Names Nobody

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.

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Reply to
.boB

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

Al

Reply to
Big Al

New Wheels, taller tires. win-win

Reply to
Backyard Mechanic

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.

Reply to
Michael Johnson, PE

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.

Reply to
Michael Johnson, PE

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
Reply to
Big Al

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

Al

Reply to
Big Al

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.
Reply to
Scotter

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