Ogre has a page on his site (from his home page linked at the bottom of the forum pages go Powertrain -> Axle & Tranny -> Gears Ratio) that describes how a sprocket and chain system in the stock automatic transmissions affects the final drive ratio. I could have missed it but I don't think there's any discussion about there being a sprocket and chain system in the manual transmissions but there is a table about half way down the page, labeled "Gear Ratio" that shows the gear ratios for the automatic and manual tranmissions. In the table, the last column shows final ratios for the manuals only. My question is: Are the final ratios in that column the number of rotations of the engine per rotation of the rear wheels in the highest gear?

If this is the case then the highest gear ratio for any of the manuals is the 4 speed econo in the last row of the table and it strikes me as weird that the 5 speed transmissions doesn't have higher gearing in 5th than the econo 4 speed has in 4th

I have an 84 Indy with a 4 speed and I assume it's the performance version because I rev a little more than 3K at 65 MPH. I always feel like I should have one more gear and sometimes I still absent mindedly try to up-shift out of 4th as I'm getting onto the highway.

Also is there a way to tell the difference between the 4-speed manual transmissions by sight?

Thanks
Bryan

quote Originally posted by Bryan96: Also is there a way to tell the difference between the 4-speed manual transmissions by sight?

There are 3 different 4 speed transmissions....MY8, M17, and M19.
The MY8 (econo) and M19 (sport) were both in 1984 and have a different case than the 1985 and 1986 M17 transmission,
You can see the case differences on this thread.

https://www.fiero.nl/forum/Forum2/HTML/063783.html

MY8 A real slug...but fantastic mileage with that tall ratio...You can get up to 42 mpg...

M19 The other extreme....good performance around town, but high rpm on the highway.....as you noted. Makes the Duke almost peppy.

M17 In the middle.....nice performance and less rpm on the highway......sold originally with the V6 only.

You can search for threads where enterprising forum members have built hybrid transmissions using gears from more than one...to try for that illusive perfect gear set.....

[This message has been edited by Gall757 (edited 11-05-2014).]

I have the m17, 3.65 ratio. On the highway you are about 3000 rpm at 70 mph. The M17 is the toughest and does the best 1/4 mi. performance but on the freeway you really want a taller gear. It's like the engine is searching at that speed. However, I have a v8 on mine now, and it is an exhilarating launch.

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quote Originally posted by Bryan96: My question is: Are the final ratios in that column the number of rotations of the engine per rotation of the rear wheels in the highest gear?

It is the ratio of the diff. You need to multiply that by the ratio of the gear you are in, to get the total ratio. This result is the ratio of output shaft speed, to the input shaft. The tire diameter will further affect that ratio to determine what speed you travel at on the road.

You can only tell the m19 trans apart from the MY8 & M17. The M19 has a much more heavily reinforced case. The other 2 are identical on the outside and were only used with 4cyl engines. The best way to tell is by the year fiero it came out of. If its an 84 then by taking it for a drive.

M19 = plentiful 85-86 only. Getrag replaced it late in 86.
M17 = common but only used 84 model
MY8 = factory econo model. Rarely seen. Some estimate only about 2000 made. I have never seen exact numbers and I don't believe they were tracked.

Sorry that info is wrong. tranny ratios

The M17 came on the v6's. It is the stoutest of the trannies. The M19 was an 84 high ratio tranny. The MY8 was the econo tranny with low gear ratio.

Arn

I've built a franken-fourspeed using the M17 first gear, second gear and case with the MY8 third, fourth and ring & pinion. I built it for a customer, so I never drove it. The Muncie is dirt simple inside, and only has one shift rail.

I've always thought that the Isuzu trans with the Fiero 3.35 final and Lotus 3.33 first gear set would make a good box for a 4.9, as long as the Lotus 2nd gear is stronger than the GM 2nd gear.