Taller top gear makes a real difference (10%) - Page 4 - Fuel Economy, Hypermiling, EcoModding News and Forum

MazdaMatt · 12-09-2008, 03:55 PM

Haha... sorry if my shiny new sports car is out of your expertise...I just read that article... interesting... very easy... only question is, what does he mean by "unstake the bolts"? Are they bolts with a pin through them or something?

Did he swap in a different ratio in that article or just replace a worn out gear?

MazdaMatt · 12-09-2008, 03:59 PM

Mazda Familia - Wikipedia, the free encyclopedia

OH MY GOD! My car has a deisel option somewhere else in the world! Hm, i wonder what the gearing is like on THAT guy

Volones · 12-09-2008, 04:02 PM

It leads me to believe that there is either a shear pin, or key or some such that holds the gear retaining nuts in place. I think he just replaced 5th with the same gear, but the procedure would be the same whether or not the ratio was changed.

BTW, I refreshed my memory and the F5M is the earlier of the F-series transmissions, while the F25M is the latter version. According to the second link, it doesn't seem to depend on the engine being SOHC, or DOHC. Also the A26M-R is a manual even though there is an 'A' in the name.

The A26M-R might just work in your Protege5 MazdaMatt, IIRC the MS-Protege was a '03 model year, so that would be good for you. I'd sure love to shoehorn that critter into my MX-3 though!

MazdaMatt · 12-09-2008, 05:57 PM

Oh yeah, i forgot to mention that I have a 2.0 L FS-DE DOHC I4. Funny how just 2 years ago I was considering changing to the FS-DET (turbo), and now i'm considering making the gears taller... my how things change.

1337 · 12-09-2008, 07:01 PM

Quote:

Originally Posted by Volones

1337, you have a Mazda F5M, or F25M transmission in your protege. The difference is the F5M came with the SOHC engine and the F25M came with the DOHC engine. I believe you can swap the 5th gear from a Mazda 626, but that may be the G-series tranny instead of the F-series. I have the F25M in my MX-3, and plan on swapping in the transmission from a 1.5L SOHC Protege when I can afford to. The individual gears are the same, but the final drive is 3.4:1 instead of 4.1:1

I'll try to find the link I have for the Protege transmission info in a few minutes.

Cheers,
Vol

Edit//
Here's a link regarding swapping 5th gear in a Mazda F-series transmission
MX-3.com - View topic - 5th gear replacement (F-series)
Hopefully, you won't need to be a member, and even though this isn't your car, the transmissions are the same for this procedure.
Best of luck!

Here's the link I was looking for...
Protegé FAQ - Transmission Info
Lots of great info here. Anything with an 'M' is a manual, anything with an 'A' is an automatic (in case you get easily confused like I do). Have fun!

Volones,

Thanks for the help. I'm pretty sure I have the F25M, because the 1.6L is DOHC. (Unless someone knows of an SOHC version of the 1.6... if you trust Wikipedia, there is only a DOHC 1.6 Mazda Familia - Wikipedia, the free encyclopedia )

Protege FAQ gives a table of the Protege models that come with the F25M, but does anyone know what other cars (probe? escort?) also use F25M or at least the same gear design as the F25M?

Sidenote: Less than a year before I bought my Protege, the previous owner had the transmission replaced at a shop (the owner paid $2500 for a new clutch and trans on a $3000 car). Is there a chance the shop could have installed a non-F25M transmission?

Volones · 12-10-2008, 10:16 AM

Quote:

Originally Posted by 1337

Volones,

Thanks for the help. I'm pretty sure I have the F25M, because the 1.6L is DOHC. (Unless someone knows of an SOHC version of the 1.6... if you trust Wikipedia, there is only a DOHC 1.6 Mazda Familia - Wikipedia, the free encyclopedia )

Yes, the '92-'93 model years Mazda MX-3RS came with a SOHC B6 engine. Check out this wiki page about the Mazda B-series engines...
Mazda B engine - Wikipedia, the free encyclopedia

Quote:

Originally Posted by 1337

Protege FAQ gives a table of the Protege models that come with the F25M, but does anyone know what other cars (probe? escort?) also use F25M or at least the same gear design as the F25M?

Yes, the previous article explains which cars used which engine, so that should help.

Quote:

Originally Posted by 1337

Sidenote: Less than a year before I bought my Protege, the previous owner had the transmission replaced at a shop (the owner paid $2500 for a new clutch and trans on a $3000 car). Is there a chance the shop could have installed a non-F25M transmission?

Yes again. It is common for people in the MX-3 community to swap their F-series transmission for a G-series one when they add a turbo. The F-series has trouble when the engine can produce over ~200ft/lbs torque and has a tendency to shred gears, especially 3rd and crack cases. The G-series has a more robust case and stronger gearset, so that's why they use them. Evidently it's a pretty straight forward swap too.

1337 · 01-17-2009, 10:16 PM

I haven't touched the Protege for a month, since I left it at college while I went home for break. Anyway, I did a little more research on what 5th gears I could put in my Protege.

To covert from engine/model (eg. '00 Protege 1.6L) year info to a Mazdaspeak powertrain (eg. ZM-DE), these articles are useful:
Mazda Z engine - Wikipedia, the free encyclopedia
Mazda B engine - Wikipedia, the free encyclopedia

In Mazdaspeak, my engine is the ZM-DE engine,

Then look at Protege FAQ's article on transmissions...
Protegé FAQ - Transmission Info

According to Protege FAQ, my ZM-DE has an F25M-R transmission. This particular F25M-R has a .775 5th gear and a final drive of 3.850.

There are two American market Proteges with an F25M-R transmission and taller 5th gears:

'92-'94 Protege with B8-ME (1.8L 16V SOHC engine)
5th gear: .731 Final drive: 3.619

'92-'94 MX-3 with B6-E (1.6L 16V SOHC engine)
5th gear: .731 Final drive: 4.05

I think the easiest thing to do would be to find a '92-'94 1.8L SOHC Protege and to swap the 5th gear into my Protege. I don't remember the exact number, but I think my Protege does 3000 rpm at 65mph. The new 5th gear would be 3000*(.731/.775) = 2830 rpm.

Now, I'm debating...is it worth my time to do a gear swap, just to lower my engine speed by 170 rpm?

Big Dave · 01-18-2009, 02:21 PM

A taller gear did wonders for my truck. Replacing 3.73s with 3.08s gained me 3 MPH on a 20 MPG truck. Now I go down the road turning 1700 RPM @ 70 MPH.

Gotta watch taller gears if your vehicle is an automatic. Less flow through the cooler will lead to spectacular (parts and ATF scattered down the road) automatic transmission failures. If you have a manual, you are golden.

Ford Man · 01-18-2009, 07:36 PM

The next set of tires I put on my '88 Escort are going to be over sized, probably going from a 185-70-13 to a 185-75-14 which will be an increase of 7.5%. I should get some noticeable increase in FE and don't have to get my hands greasy.

Big Dave · 01-19-2009, 12:24 AM

A lot of guys in the pickup truck community have tried larger diameter tires and the empirical result is always the same: Larger diameter tires result in lower MPG.

Wheel and tires are "flywheels" that have to be accelerated everytime you pull away from a stop. The energy stored can be tapped to a limited extent by a skilled hypermiler, but mostly gets wasted.

Forget the tires and get taller gears.