When will the GT get a 6-speed?

Clunky? Ok....have you even driven a T56 03-04 cobra? I have driven 2, and HATE them. IMO they suck, mainly the clutch engaging a 1/2 inch off of the floor. I can hardly shift the 03-04s, shifter and tranny really isnt very smooth IMO. The 03-04s are fast as heck stock though. Hey, what mods do you have? What RWHP? EDIT, dont hate the cobras lol, just hate the tranny.

There aren't too many 6 speeds out there.

BTW The T-56 isn't a real 6 speed and wouldn't provide any benefit over the 3650.

gp001 said:

There aren't too many 6 speeds out there.

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Sure there are. A six-speed tranny isn't all that uncommon anymore in a sporty car, but somebody forgot to tell Ford.

As another poster pointed out, the Nissan Sentra can be had with a six speed. The Acura RSX is available with a six speed, as is the Mazda RX-8 and the Nissan 350. Even the retired F-Bodies had a six speed.

Although it doesn't seem to be hurting sales any, a six-speed would be a welcome addition (even if optional) to the GT at least.

jfischer said:

Sure there are. A six-speed tranny isn't all that uncommon anymore in a sporty car, but somebody forgot to tell Ford.

As another poster pointed out, the Nissan Sentra can be had with a six speed. The Acura RSX is available with a six speed, as is the Mazda RX-8 and the Nissan 350. Even the retired F-Bodies had a six speed.

Although it doesn't seem to be hurting sales any, a six-speed would be a welcome addition (even if optional) to the GT at least.

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So, you want Ford to design an entirely new transmission? Because aside from the T-56 (which isn't really a 6 speed) all the other current 6 speeds that can be adapted to a rwd v8 ford are kinda pricey.

hotmustang331 said:

Clunky? Ok....have you even driven a T56 03-04 cobra? I have driven 2, and HATE them. IMO they suck, mainly the clutch engaging a 1/2 inch off of the floor. I can hardly shift the 03-04s, shifter and tranny really isnt very smooth IMO. The 03-04s are fast as heck stock though. Hey, what mods do you have? What RWHP? EDIT, dont hate the cobras lol, just hate the tranny.

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Sounds like you hate the clutch, not the 6 speed transmission.

That being said, there is no real need for a 6 speed in the base model or the GT, for the same reason that there is no real need for more than 300 HP.

Bryanzstang has already proven that 13.4s are already possible with a stock 5 speed GT. For most people that are buying a "sporty" car or a muscle car, that's more than fast enough, especially since most Mustang owners will never take their car to a track or mod it. When 90%+ of cars being sold are automatics, how can anyone make a business case for adapting or designing a new 6 speed in the $25,000 GT? Would you have paid another $2000, $3000 for your GT to have had that 6 speed as an option?

The real question is this. When you look at the difference in gearing ratios between the 5 and 6 speed. I believe the final number comes out at .02 difference. So what REAL benefit is the 6 giving? Or is this really just a my trans is bigger than yours issue?

Here is some info I posted regarding this topic on another forum (They PM'd me to be involved since they knew that I had done a 6 speed swap in my 66 Mustang). Let's hope any discussion that evolves here has more thought than it did over there

Hey guys,
First off, why would anyone take the time to convert from the 5 speed to a T-56? All you are getting is 2 overdrives. Not really a performance mod.
I have been throwing around the idea of putting a Richmond in my 05, but nothing serious yet. I'll think about this a little more and post later if I think of anything.

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Where do you guys get your info?

The 2005 GT 3650 3.38 2.00 1.32 1.00 0.68
Ford spec T-56 -- 3.36 2.07 1.35 1.00 0.80 0.62
------- or ------- 2.97 2.07 1.43 1.00 0.80 0.62
Viper spec T-56-- 2.66 1.78 1.30 1.00 0.74 0.50

Explain to me how the T-56 (any gearset version) would be such a benefit over the 3650 dunno.gif

An overdrive gear should NEVER be used in a performance situaton, and I seriously doubt any of you will ever see speeds in the overdrive range for more than a short period, on a freeway, never at the track.

0.62 aint a big difference over 0.68, and while 0.50 may seem great for steep rear gears the 2.66 first pretty much negates it.

I did a TON of research befre putting the Richmond 6 speed in my 66 and would suggest anyone contemplating doing a tranny swap on their 05 do more research than "hey, they put the T-56 in the GT-500 and the Viper".

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Too funny, thanks for the laugh after a long day.

I am well aware of how to calculate rpm/mph for gear ratios. When I was researching my tranny swap for my 66 I made a program that allowed me to input trans ratios, rear ratios, and tire sizes and it would generate a table of mph for gear ratio/rpm combinations. Here is the html version of the chart for the setup I went with

http://www.2mfffabshop.com/mycar.htm

If you really want to reduce your cruising rpm by 300 try driving at 74 mph, it would be alot less money and hassle.

If you are that dead set on putting a T-56 in your Mustang because that is what they put in the GT500 then more power to you. thumb.gif

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i actually love the tranny in my car. it shifts extremely well, and the gear ratios are great, as is the clutch. on the highway, cruising at 80, the rpms are nice and low, and it gets good gas mileage. the riceburner hondas have six speeds because they have weinie engines and they need all those gears to actually make the car driveable. the mustang has big fat hairy nalls under the hood, so it is fine with a 5 spd with a good 5th gear.

What does one get with a 6 speed over a 5 speed when you have a V8 ?

Better performance (0-60)? Better highway mileage (steady 65MPH cruise)? Both? Neither? Just more shifting?

PhantomGT said:

I just watched a Mitsubishi Eclipse commercial on TV and this new Eclipse comes with a 3.8L 260 HP V6 with a 6-speed transmission. Now our cars come with a 300 HP 4.6L V8 with a clunky 5-speed out from the Old Testament. So at what point will these Ford Engineers drop a 6-speed into this car, because this car really needs one! Even the Nissan Sentra has a 6-speed option and Brembo’s!

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Personally I'm not sold on this more gears is better theory.


It depends what you want from a car. If you had the current box and added a 6th it would work like an OD giving really good cruising mpg at low engine rpms, but it wouldn't really help in accelaration. This is exactly what the Corvettes and Fbody's face. Unless producing massive BHP their top speed will nearly always be in 5th NOT 6th as they just don't have the power to pull 6th at high speeds.

The other option would be to close all the the other ratio's up. So 6th could have the exact same ratio as your current 5th.

This in theory would allow better in gear accelartion but at a cost of a lower terminal speed in each gear. Another down side is that you would have to change gear more often and changing gear means not accelarating and costing time.

And modern diesels and revvy 4 or 6 cylinder engines with a narrow power band 6 speeds help keep the engine on the boil. A grunty V8 like the Mustang does not need it as it has a much broader powerband.

Take a look at the new TVR Sagris, it will do
0-60mph in 3.5 seconds
0-100mph in 8.7 seconds
0-150mph in 20.0 seconds
and top speed in excess of 180mph

It will do 60mph in 1st and over 100mph in 2nd. It only has 5 gears.

The new Z06 is probably similar, I know it is geared to do 60mph in 1st, so most of its performance and probably top speed will be with 5 gears and 6th will be an OD for mpg crusing. Which is very handy but not essential.

There are some C6 owners claiming 29+mpg @ 70mph on the highway with the a/c on. - a real bonus of the long legged 6th gear.

If top speed is not needed a good old 4 speed gearbox is about bang on, but for a fast car it will normally limit your top speed to 110-120mph and crusing mpg will be non existant.

It's also worth noting that many modern 5 speed boxs run the same ratio's as a 4 speeder with an OD for 5th.

A 4 speed box would usually have 1:1 4th gear, a 5 speeder will usually retain that ratio for 4th (hence dyno runs should be done in 4th) but 5th will be 0.xx:1 ratio.


Modern sequential boxes can change gear very fast such as the new 7 speed box in the new BMW M5, but they have other drawbacks for street use. Auto's can also shift much quicker than a manual can and could benefit from more gears like the 5 speed ZF box in the Jaguar XK8, this was added as an OD however top speed is still in 4th. Too many gears in an auto an it will loose some of its refinment and be constantly shifting. My 3 speed XJS is very smooth and hardly ever changes gear, the downside is slightly more lack luster accelaration.


Having driven a few 6 speed cars with close gearing you'll notice another downer. You seem to spend your entire time shifting, your right arm (for LHD cars) will spend more time on the gearstick than on the steering wheel. As each gear will have a very limited speed range compare to a normal 5 speed.

Personally I love the V8 grunt and love just crusing in my TR7 where I can leave it in 4th most of the time, with the knowledge that it will pull from 20-105mph no problem and still be faster than 80+% of the cars on the road.

However each to his/her own. If the alure of a 6 speed appeals there is no reason you can't fit one after market.

I spent some time a few months ago with friends in Australia who have a new Holden Commodore (looks like an old Caprice) with the 5.7-litre GEN-V (Corvette) V8 and a six-speed. Nice fast car but, traffic was such that for the most part, the guy just drove it like a three-speed: 1st, 3rd, 5th. It seldom got into 6th.

I don't miss the extra gear in my 05 GT convertible. I love how this 5-speed shifts.

I drove a 350Z with a 6-speed recently. Never got the thing out of 5th. Of course, I was not on the interstate. I'm not certain more gears are better either. Just more shifting and I'm getting too old for that.

I drove an 05 gt this weekend and it was a much better shifting car than the 04 cobra I drove last year.

More gears are better if you road race. You have more selection to keep your car in it's power band. For drag racing or street driving there really is no benefit.
With that said, I do plan on fabbing up a Richmond 6 speed in my 05 when I build a new motor (currently looking for wrecked 05s with motor and pcm for sale). I will be doing it because I plan to build some decent power levels and want a trans I know can handle it. Oh, and I've been designing a sequential shift mechanism for it as well Should be interesting

One benefit to the higher overdrive with the 6 speed is mileage. M6 Fbodies and Vettes can easily hit 30 MPG on the highway due to the overdrive.

The mileage out of the 4.6 V8 isn't really that impressive, an additional OD gear would be nice for those who do some highway driving...

gp001 said:

Oh, and I've been designing a sequential shift mechanism for it as well Should be interesting

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Cool, you'll keep us updated I assume?

300bhp/ton said:

Cool, you'll keep us updated I assume?

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Well of course. I started designing it for the Richmond 6 speed I put in my 66 Mustang. The throw on the shifter is LONG, and the position of the shifter was making it a nightmare for my custom console design. So, I designed a ratcheting mechanism that rotates some lobes activting the shift linkage.