Anyone experimented with gear sizes or a different transmission?

[Pat B.]

Just curious, couldn't find much online. Car is getting it replaced so I was wondering if there was a better one that could slip right in or have mine rebuilt with slightly longer first and second gears? Kind of a shot in the dark but any input is helpful, thanks.

 

[RAAMaudio]

I think you are going to find nothing else fits that would be acceptable for all the ratios even if you can find something.

Of course with serious research, tearing apart whatever Ford makes for similar cars, one might get lucky, I would start with that premise what do they make what are the ratios, not likely to find aftermarket support on a relatively low volume low cost car.

I went down this road years ago and the best I could come up with was modified stock 5 speeds into 5 or 6 speed LSD equipped, race spec transaxles with a minimum order of 10 and 6 months waiting time, $60k deposit.

 

[jeffreylyon]

It's an IB5 gearbox which is used in lots of Ford, but the ST's 6-speed version is new. Quaife does some interesting stuff for the 5 speed, including a dog box and a sequential gearset, but, again, it's all for the 5-speed version and not cheap. An IB5 from a diesel might have a longer 1st and 2nd but I think that you'd be better off just fitting some 215/45s for longer legs. Maybe you can find the final drive from one of the european eco-versions, but who knows if it'll survive the ST's torque.

 

[me32]

If you have the tranny out i say install a LSD

 

[GAbOS]

I just want a longer 6th

 

[me32]

I just want a longer 6th

Why do you need it?

 

[GAbOS]

Mpg

 

[jeffreylyon]

You're going to have a hard time finding a 6 speed IB5 with a close ratio 1-5 and a longer 6th, even with a custom gearset. You could probably find eco-versions of the 5 speed, which may or may not be destroyed by the FiST's torque, or find a longer final drive which will effectively lengthen every gear (as would going to a taller tire). All of the motorsport stuff, which is build to last with hp engines, will shorten ratios, not lengthen them.

You could try to fit an MTX 75 into a FiST...

 

[Pat B.]

Don't have the money for the lsd or else I would have. its getting replaced with a new factory unit for now. Tranny upgrades in the future would be nice to see.

 

[jeffreylyon]

Well, there are upgrades, but tranny upgrades are usually for the motorsports crowd, who doesn't care much about mpg.

 

[me32]

Mpg

Taller tire =Longer gear, better freeway mpg. Other option is keep it at 65mph and 35mpg is easy

 

[GAbOS]

The speed limits I use the most in a drive are 65 and 70, which means I do 75-80 most of the time but even still. The taller final still has this thing in boost. We actually should be as lucky to have the gear ratio we do. If finals were easier to obtain, I would be all over it. A 3:50 or so would be okay.

 

[me32]

The speed limits I use the most in a drive are 65 and 70, which means I do 75-80 most of the time but even still. The taller final still has this thing in boost. We actually should be as lucky to have the gear ratio we do. If finals were easier to obtain, I would be all over it. A 3:50 or so would be okay.

I drive in the same mph and get 31-32mpg. Going with a taller tire would allow you to run at a lower rpm at 75-80mph

 

[Chiburbian]

The taller final still has this thing in boost.

Just to keep the language specific, you are likely not driving in boost at 65/75mph. You may however be driving within the boost threshold.
https://www.turbobygarrett.com/turbobygarrett/node/117

A. Boost threshold is the engine speed at which there is sufficient exhaust gas flow to generate positive manifold pressure, or boost.

Q. What is Boost Threshold?

If you were in boost you would be getting single digits highway milage.

 

[jeffreylyon]

If finals were easier to obtain, I would be all over it. A 3:50 or so would be okay.

Quaife has a bunch of final drive options for their sequential gearset for the IB5. If they've got something suitable for you I'm sure they'd sell it to you outside of the complete gearset.

 

[TrickSTer]

MPG @ hwy speeds> Economy Tune

 

[jeffreylyon]

MPG @ hwy speeds> Economy Tune

Does the Cobb OTS economy tune do anything more than limit boost?

 

[Joker328]

Does the Cobb OTS economy tune do anything more than limit boost?

I think I read somewhere that it is a hair leaner than the other tunes, but not sure how much difference it makes.

 

[BlueBullet]

I have 215/45 tires and at 70 on the speedo I read pretty close to 75 mph on the gps. I thought that the longer gear ratio would help mpg also and that is why I opted for this set up but I found that if anything it was the opposite that happened. I have done a few more mods and changed tunes but I used to get 31 mpg around 75. Right now I am seeing about 28 mpg no matter what speed I drive. The reason I suppose is that looking at the estimated tq (which does seem to be directly related to vacuum psi and mpg) has gone up a fair amount after changing wheel size. I think that the added tq requirement to get the car down the road as actually costing me. I used to run about 55 tq output at cruise speeds and now see 65-70.

 

[BGPunk2001]

So, let me understand this... You would drop a crapload of money to swap out a transmission or individual gears so that you could save money on fuel?