can you take a 4.10 4 spd final drive and swap it into a, say 3.65 5 spd. Reason i ask is because on the way back from BC my tranny locked itself into 4th gear and it sounds like (after i did some searching on the forum) others have experienced the same problem and it is an internal issue. Thought i might as well swap in a 5 spd if i have to switch out trannys but in a perfect world id rather keep my 4 spd because of the 4.10's.
Thanks!

If someone could post a link to the gear ratios for a 1987 gt 5 speed that would be cool too.

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Email: adriantalliss@email.com
1984 Indy Fiero 4spd 3.4L
-Est 220hp @ 5000rpm / 230 tq @4500rpm, centerforce II clutch, 390cfm 4bbl holley, crane h272 cam, Edelbrock Torker II intake, 9 to 1 comp, minor head porting,headers, true 2" mandrel dual Supertrapp exhaust, factory 4.10 4 spd, 17x7 white Konig Ziege FR 205/40R17 RR 235/45R17. All interior leather changed to white, custom built adj aluminum rear wing, aftermarket gauges, corvette MBC upgrade, Held coilover kit, 2 inch drop front and back.

[This message has been edited by donk316 (edited 08-05-2003).]

found half of my question. credit given where credit due. plus if anyone else searches the forum this willl come up!

General Information
MD9 3-SPEED AUTO 125THC ONLY AUTO USED
MG2 5-SPEED MANUAL MUNCIE 3.61 RATIO V6 ONLY
MT2 5-SPEED MANUAL ISUZU 3.35 RATIO L4 ONLY
MY8 4-SPEED MANUAL MUNCIE 3.32 RATIO 1984 L4 ONLY
M17 4-SPEED MANUAL MUNCIE 3.65 RATIO V6 ONLY
M19 4-SPEED MANUAL MUNCIE 4.10 RATIO 1984 L4 ONLY

Note: MG2 is the Getrag-designed Muncie built transaxle
Note: the V6 Muncie is stronger than the L4.

Gear ratios for manual transaxles
Final
1st 2nd 3rd 4th 5th Drive RPO
1984 L4 3.53 1.95 1.24 0.73 3.32 MY8
1984 L4 3.53 1.95 1.24 0.73 4.10 M19
1985 L4 3.73 2.04 1.45 1.03 0.74 3.35 MT2
1985 V6 3.31 1.95 1.24 0.81 3.65 M17
1986 L4 3.73 2.04 1.45 1.03 0.74 3.35 MT2
1986 V6 3.31 1.95 1.24 0.81 3.65 M17
1987 L4 3.73 2.04 1.45 1.03 0.74 3.35 MT2
1987 V6 3.50 2.05 1.38 0.94 0.72 3.61 MG2
1988 L4 3.73 2.04 1.45 1.03 0.74 3.35 MT2
1988 V6 3.50 2.05 1.38 0.94 0.72 3.61 MG2

Gear ratios for automatic transaxles
1st 2nd 3rd
MD9 2.84 1.60 1.00

Final
Drive Code RPO
1984 3.18 PF MD9
1985 3.06 CD MD9
1985 3.18 PF MD9
1986 3.06 6CD MD9
1986 3.18 6PF MD9
1987 3.33 7CPC MD9
1987 2.84 7PSC MD9
1988 3.33 8CPC MD9
1988 2.84 8PSC MD9

From PENN-JERSEY FIERO CLUB NEWSLETTER No. 9, corrections and additions from Scott Backer

Email Eric at WCF. They have had some posts about mixing and matching gears, but I can't find the post I want. He'll be able to tell you the ideal set to use.

Thanks i will.

So as for a lesion is gearing let me see if I got this right...The larger the gear number say 3.65 means more revolutions
over the RPM's of the engine...Meaning if you would like a nice overdrive on an AUTO it would be like 3.??

I'm so confused about the gearing, and how each gear breaks down to its drive number,
but there is a total drive number....Can someone please explain...

Would it be like say a trani with a total final drive of 4.10 means it turns 4.10 times for 1.0 RPM of the engine..??

So does the General Information chart mean that on the L4 Muncie 4.10,
in forth gear, you can cruz at lower RPM's, than in the 5 gear of the MG2 Getrag at 3.61??

Basically what I want is a tranni that starts out low, and builds up where I can get on
the freeway and cruz at 3,000 engine RPM's, and 110 MPH in 5th gear....

Here in the Bay area, the freeways are like race tracks, and everybody does at least 80 to 100 mph...

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quote Originally posted by Seanpaul: ... So does the General Information chart mean that on the L4 Muncie 4.10, in forth gear, you can cruz at lower RPM's, than in the 5 gear of the MG2 Getrag at 3.61?? ...

Actually the numerically higher number is a 'lower' gear. The 4.10 will actually cuise at a higher rpm. The 5spd is ACTUALLY half a second slower in the quarter mile because of the difference in gearing! The 5 spd is a better choice for high mph cruising where as the 4.10 4 spd is an acceleration geared tranny.

quote Originally posted by Seanpaul: Would it be like say a trani with a total final drive of 4.10 means it turns 4.10 times for 1.0 RPM of the engine..??

Total ratio = current gear times final drive.

4.10 Muncie in 4th gear: 0.73 * 4.10 = 2.993

That's the number of times the engine turns for 1 revolution of the axle.

Getrag in 5th: 0.72 * 3.61 = 2.5992

Since the engine turns fewer revolutions for each revolution of the axle with the Getrag than with the 4.10 Muncie, the Getrag gives lower RPM at cruise than the 4.10 Muncie.

The final drive ratio means the number of revolutions the engine makes in relation to one turn of the wheels.The higher the number the more revs the engine turns to turn the wheels a given speed.

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#1112
Question my ability,question my intelligence,never question my integrity!

quote Originally posted by Will: 4.10 Muncie in 4th gear: 0.73 * 4.10 = 2.993

That doesn't make any sense to me...hummm...Do you mean that the 4th gear is 0.73 and then you
times it by 4.10 and it = the final drive number..?? I though 4.10 was the final drive number for that tranni..?

[QUOTE]Originally posted by Seanpaul:

Getrag in 5th: 0.72 * 3.61 = 2.5992

(This was first quoted by Will, I believe)

What this means, is that the rear axle is turning at a little over 1/3 the revs that the engine is turning.

More precisely, Rear Axle RPM = Engine RPM divided by 2.5992

As an example, you can calculate the MPH at any engine RPM, if you know the rear tire circumference. It happens that the 215/60s on an '88GT have a tire circumference of 79.8", or 6.65 ft. So, the car moves ahead by 6.65 feet for every revolution of the rear axle. There are 5280 ft in one mile and 60 minutes in one hour, so the calculation goes like this:

(Assume an engine RPM of 1000)

Rear axle RPM is 1000 divided by 2.5992 which equals 384.7

When the rear axle is turning at 384.7 RPM, the car moves forward (6.65 X 384.7) = 2558.2 feet each minute. Divide this by 5280 and multiply by 60 to convert to MPH, and you get 29.07 MPH at 1000 RPM engine speed.

So, at 2000 RPM, the car is going 58.1 MPH, and at 3000 it would be 87.2 MPH, etc.

The above is for 5th gear, but you can do the same for the other gears by using the overall ratio for that particular gear.

While this is mathematically correct, there is some increase in tire diameter (and hence circumference) at high speeds, due to centrifugal force, but this is beyond the intent of this thread, which was about gearing.

Hope this is useful to some of you.

...Rickker

[This message has been edited by Rickker (edited 08-07-2003).]

[This message has been edited by Rickker (edited 08-07-2003).]

quote Originally posted by Seanpaul: Getrag in 5th: 0.72 * 3.61 = 2.5992 So by this calculation...the getrag 5th gear (times the final drive) means you're engine is doing 2.5 RPM's to turn the axel once..? So is the final drive number just the unrelated number used for calculation purposes...? I don't understand the relation of the final drive number.... how do you calculate the final drive number....

Drivelines are almost universally two or more stages of reduction. In all the manual transaxles used in Fieros, there is an input shaft with 5 forward gears, and an output shaft with 5 forward gears and 1 final drive gear, which drives the differential ring gear. The ratio from the selected input shaft gear to the corresponding output shaft gear is the selected gear ratio. The ratio of the pinion on the end of the output shaft to the ring gear on the differential is the final drive (AKA differential or rear end ratio). The overall ratio is the product of the selected gear ratio and the final drive ratio.