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Discussion Starter · #1 ·
Seriously. Why is the 5th gear manual tranny geared (including final drive ratio effect) so much shorter than the 5th gear in the automatic? Especially 6th gear? I'm discovering this is not just a Mazda phenomenon, but several manufacturers of cosnudmer sedans have short top gears with the manual transmissions, despite having an extra gear over the automatics.

Do we really need such tight transmission ratios between both 4th/5th (1.226) and 5th/6th (1.167)? As geared, 5th and 6th both provide less "delta MPH" (MPH gained in each gear upon returning to the same RPM level as you had in the prior lower gear at the time you upshifted) than do 3rd and 4th. A diminishing returns effect. I don't understand the designers' motivation to group it so tightly. 3000 RPMs at 74 MPH is a bit much in my opinion. Should be more like 2500 in 6th. The torque band on the 2.5L is pretty generous, and the engine responds very well at "low" RPMs like 1500. Plus the engine has very pleasant and low tone around 2000 RPMs that is suitable for highway cruising.

Shifting at a moderate 3000 RPMs, RPM drop is only 550 and 650 going to 5th and 6th gears, respectively. In fact, if you plot it, RPM drop for each gar paring is almost a perfectly straight line (decreasing as you upshift) except for 5th to 6th. A curve with drop flattening out a bit would have been more appropriate, as you see with atuomatic pairings. I'd say we'd be better off with a taller 5th (.78 versus .84) and taller 6th (.60 versus 0.72). That would have the car at 2000 RPMs at 59 MPH. For 4t, 5th, and 6th, it would also have the higher gear at 1500 RPMs being at about the same speed as the lower gear at 2000 RPMs. A nice arrangement for tepid city driving with downshifting and upshifting with little need for brisk acceleration.
 

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Discussion Starter · #3 · (Edited)
But I really enjoy having a manual and I like the non-loss of power that an automatic would otherwise bring.

We have six gears, and it's hard to understand why they would not want to build a taller top end into the transmission. There is plenty of performance to be had with a well spaced 6 gears with a taller 6th than the current one. 1 through 4 on the current box are essentially OK. 5 and 6 are the ones I don't understand.

Are the designers afraid we won't know to downshift out of 6th at 35 or 40 MPH if they had a taller 6th? I mean, dang, I can can accelerate out of 28-30 MPH in the current 6th with no issues. Or do they think that just because I have a manual tranny, I want to drive around over 3000 RPM all the time so at to be at the top of the torque curve during my commute? I'm not racing, after all.

A taller 5th would have PLENTY of overlap with the current 4th, and a taller 6th could then easily follow with no performance issues.

I've spotted some aftermarket replacement gears for Hondas on the web. Are there any available for Mazdas? It would really be nice if Mazda would make it an endorsed alternate configuration.
 

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I agree. What are the ratios in a speed3 transmission like? If I pull one out of a speed, can I throw it in my 2.5 GT? I'd love it if 5th and 6th gears were, you know, useful. Maybe 6th as 5th and a bigger, actually worthwhile 6th....
 

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But I really enjoy having a manual and I like the non-loss of power that an automatic would otherwise bring.

We have six gears, and it's hard to understand why they would not want to build a taller top end into the transmission. There is plenty of performance to be had with a well spaced 6 gears with a taller 6th than the current one. 1 through 4 on the current box are essentially OK. 5 and 6 are the ones I don't understand.

Are the designers afraid we won't know to downshift out of 6th at 35 or 40 MPH if they had a taller 6th? I mean, dang, I can can accelerate out of 28-30 MPH in the current 6th with no issues. Or do they think that just because I have a manual tranny, I want to drive around over 3000 RPM all the time so at to be at the top of the torque curve during my commute? I'm not racing, after all.

A taller 5th would have PLENTY of overlap with the current 4th, and a taller 6th could then easily follow with no performance issues.

I've spotted some aftermarket replacement gears for Hondas on the web. Are there any available for Mazdas? It would really be nice if Mazda would make it an endorsed alternate configuration.
I bitched about this after owning the car for a bit, especially to effect mpg...they could easily get another 2-3mpg on there rating with some gearing...6th truely is an overdrive and a pathetic 1 at that. this is the first manual ive even had where driving at 70 im half way through the rpm range. i think i use 5th gear maybe 3 times a month
 

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Dustin L.
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As stated above, 5th and 6th are close ratio so that they are useful. I actually like the fact that 6th isnt just a highway gear. To each their own but I'm lazy sometimes and down shifting is a pain. I like that I can just press the gas to pass people. Just recently read a write-up on the new Viper and the engineers over the project did the exact same thing with it. 6th is a useful gear not just for granny to putter around town.
 

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The gearing is a little odd and I agree that 5th and 6th are too close together. Most of the time when the auto makers migrated from 5 to 6-speed transmissions they kept the over all top and bottom gear ratios the same and just devided things up into 6 ratio's versus 5.

Another factor is marketing. The US auto market is obsessed with 0-60 and accelelration numbers. In order to deliver numbers that look good on paper, they keep the gearing a little lower.

Personally, the only change I would make is make 1st and 6th a little taller to even things out. I find when I'm in traffic I'll frequently skip 5th and go from 4th to 6th.
 

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Smells of Elderberries
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I'm going to quote myself from another thread here. the link to the original thread is here (http://mazda3revolution.com/forums/...nce/7579-its-time-2-5l-6-speed-fun-facts.html)

If you do the calculation (http://www.f-body.org/gears/) swaping 6th gear to the Mazda5 6spds gear it puts you at 2600rpm or so at 70MPH! If I was to go this far I'd also swap at least 2nd gear also it would allow for 60MPH. for faster 0-60 times. Or you can go nuts and swap out to the MZ6's ring gear.

I've been digging around and have found some fun facts on our 6spd transmission (and 5spd). It apears that the transmission is a variation of the "G" series Mazda gear box and used in anything from the Protege to 323, Mazda 3,Mazda 5, Mazda 6i, MX-3, 626, and a few Fords.

What does this mean?

I found the part# for the differential in our car shares the same part# as the Gen1 Mazda3 5spd (GC0627180).... Which happens to have a few limited slip differentials available for it. Quaife, MFactory, KAAZ and possibly a few more! W just need someone to be the Guinea pig to see if its possible for sure :tongue:

Also the g66m-r 6spd used in the 2012 Mazda5 and 2009+ Mazda6 have a few different gear ratios. Which may lead to a possible gear swap. Looks as though the 2012 Mazda5's 5th and 6th Gear would do some good in lowering 5th and 6th gear RPM's at highway speeds!

Mazda3 Mazda6 Mazda5
1st----3.45----3.45----3.45
2nd----2.06----1.84----1.84
3rd----1.39----1.31----1.23
4th----1.03----1.03----0.91
5th----0.84---- 0.84----0.76
6th----0.72---- 0.72---- 0.68
Final----4.11----4.39----4.11
 

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I like the fact about 6th gear being not so top. just so I can cruise at 40mph in 6th effectively!

also why the hell did mazda overcomplicate things with different gear ratios for diff cars? thats stupid and not productive
 

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Looks like interest in this has dropped off. Maybe I can stir something up since I'm a new owner. While doing some sleuthing of my own, I ran across the attached info (see jpg) from the CleanMPG forums. Looks like there are additional final drive and gear options for the EU spec Sky 6MT. I played around with a number crunching site and I think I may have come up with an ideal configuration. It is a blend of our current gears, some of the EU spec gears and the taller EU FD ratio.

Here it goes:
1st------3.70-----EU
2nd-----2.06-----US
3rd------1.39-----US
4th------1.03-----US
5th------0.84-----US
6th------0.68-----EU
Final-----3.62-----EU

The shorter 1st basically mirrors our current 1st thanks to the taller FD. There will be a bit bigger gap going into 2nd than we have now (1100 RPM vs 1000). From there it steps up progressively tighter with 3rd (850 RPM drop), 4th (650), 5th (450) & 6th (450).

6th gear cruising at 70 MPH would turn a leisurely 2200. Drop to 5th at 70 and jump to 2700. Drop to 4th and hit 3300. If you shifted at 2500 RPM each time you would shift at the following speeds: 15, 26, 39, 53, 65, 80. 6th is significantly taller, but the new 5th is only a bit shorter than our current 6th, so that ratio is still in the mix.

I am new to all this and I don't know all that might be involved. I'm sure the speedo will need to be recalibrated. I think that this may dovetail nicely with the improved driveability folks are reporting from the Dynotronics tuning. Could be a sweet combination since the tuning would be specific to the new gearing if the tranny work is done first. Since both changes would put my PT warranty at some risk I'd look to do the two close together in a couple years. For now I'll keep daydreaming.
 

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My personal preference ( at least on 2013 Skyactiv) would be to have shorter gears from 1 to 5 and let 6th stay as is for cruising.

I don't even find accelerating in 2nd gear satisfying. I redline often in 2nd gear, and frequently downshift to 3rd or 4th at highway speeds, but still the car feels sluggish. I do find it a decent handling car while on a curvy road though.
 
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