Transmission

Hey guys, im new to the forum. I'm thinking of buying a fiero but would
like to get the economy ratio transmission. How can you tell?

This is what the wiki page said, but i cant figure out how to tell which
tranny is in the car:

While General Motors management and accountants were opposed to
investing in a second two-seater sports car that might compete with the
Corvette, they perceived the oil crisis as a market opportunity for a fuel-
efficient sporty commuter car. To this end, the Fiero was re-designed to
use a fuel efficient version of GM's 2.5 L four-cylinder "Iron Duke"
engine capable of 27 mpg-US (8.7 L/100 km; 32 mpg-imp) in the city
and 40 mpg-US (5.9 L/100 km; 48 mpg-imp) on the highway with the
economy-ratio transmission option.

Also, are these transmissions interchangeable for that matter? Could
you put a five speed in an 84 and would it improve the mileage, or
make it worse?

Also...
I saw an 84 with 2m4 on the back, and one without, does this mean
anything or is it just missing?

Thanks for your help!07_213427_fiero_back_2m4.jpg">
07_213451_fiero_back_no_2m4.jpg">

A few quick things, as Patrick said the 5spd is better suited to the 4cyl engine, but not because of Freeway rpms. The Econo 4spd which has a 3.32 ratio top gear is actually taller than a 5spd. You do have lower rpms with an Econo 4spd on the highway than you do with the Isuzu but only by a few hundred rpms. Having 5 gears that you can split up vs. 4 gears makes the low power of the duke much easier to be in the right gear. You will find with the Econo 4spd in traffic you will be constantly changing from 2nd to 3rd gear and back. 3rd in the Isuzu is right in the middle of 2nd / 3rd in a 4spd. I would like to note, there are 3 different 4spd Fiero transaxles. The 3.32 Econo 4spd the 4.10 Performance 4spd and the 3.65 4spd for the V6. The 4.10 4spd is the one that Patrick had and is HORRIBLE on the highway, but great for zip around town.


     Now trying to find a 3.32 4spd will be a nightmare. I had a few back in the late 90's and have been searching for another for the last 10 years and can't find one. You really are better off finding an 85 Fiero that already has a 5spd in it. Plus the 85 Fiero shares most of the parts with the V6, where as the 84 is a pretty unique beast.

    Last question for ya, I am in Oregon myself at the moment. Where abouts are you down here.

This is copied from my personal website. I also have an excel spread sheet that calculates speeds and rpms in each gear with variable tires sizes and engine redlines if you are interested in that.   

Trans Info   
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How to read chart. Using 84 Econo as the example.
3.32 is like the rear end gears that number is multiplied times the individual gear ratio to find out the number of turns of the wheels in relation to the numbers of turns of the engine. In this case Most of the work is done for you. In this case 1st gear, will require the motor to spin 11.72 times for one rotation of the rear wheels. Meaning at 6000 rpms the rear wheel will be spinning 510.63 RPMS. This is a much higher rate than the 84 Perf. Ratio of 6000rpms = 414.65 in first gear. What it boils down to is the bigger the number the quicker your car will be 0-60 but also the slower you will be in top end. The smaller the number the slower you car will be 0-60 but you will be able to go say 100mph at only 2800rpms.. Now if you have a V8 or a souped up V6 you may find that the Econo Tranny can actually be faster because you can hold each gear longer. Working with a 6000rpm redline and a 15" wheels you can go 100mph in 3rd gear with Econo trans. That means you do not have to waste time shifting. Now you should have a basic understanding on trans ratios, the bigger the number the quicker you car can move the higher the number the better the gas mileage
    Just as a side note, both the 84 Transaxles
were Muncie's same as in the 85-86.5
V6 Cars. The High Ratio trans offers the highest gears of any Fiero Trans even higher than the 5spd Getrag or the Isuzu. The 4.10 Ratio is so low that unless you are an in town driver or a drag racer most find it to rev happy on the freeway.   

You have to check the RPO codes and hope that the trans has not been changed out, IIRC the Econo Trans is RPO MY8 its on the sticker under the hood.

Pop the front hood.  Look on the inner fender, right in front of the master cylinder(s).

It's about 6*5", and has a series of 3 letter/number codes.