Does anyone produce a modification to the 282 muncie-getrag to provide a taller final gear ratio (lower numerically) for the sake of mileage? I have a 350 87 Gt with a getrag 5 speed. First gear is so low as to be not needed because the engine has plenty of torque for normal takeoff in second gear. I get 20 -21 mpg regularly with it when I don't use the a/c. A final drive ratio change would lower highway cruising rpm, thereby making first gear useable and overdriving fifth gear. If I remember correctly, the stock final drive is a 3.65:1 ratio. Also what are the ratios of the individual gears in the 5 speed 282 muncie-getrag?

edit: I would like to think about a 2.75:1 ratio final drive as a starting point.

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Tom
Suffolk, Va
87 Gt 2.8 5 spd. / 87 Gt 350 5 spd.

[This message has been edited by gt7 (edited 07-08-2008).]

bump...

a company called webster gear used to supply the custom gear sets for some of the road racing trans that pontiac used in the racing fiero's back in the 80's. i don't know if they are still around.

quote Originally posted by gt7: Does anyone produce a modification to the 282 muncie-getrag to provide a taller final gear ratio (lower numerically) for the sake of mileage? I have a 350 87 Gt with a getrag 5 speed. First gear is so low as to be not needed because the engine has plenty of torque for normal takeoff in second gear. I get 20 -21 mpg regularly with it when I don't use the a/c. A final drive ratio change would lower highway cruising rpm, thereby making first gear useable and overdriving fifth gear. If I remember correctly, the stock final drive is a 3.65:1 ratio. Also what are the ratios of the individual gears in the 5 speed 282 muncie-getrag? edit: I would like to think about a 2.75:1 ratio final drive as a starting point.

This is exactly what I am after but I have not seen a solution for this.

Steve

The stock ratios are:
1st 3.50
2nd 2.05
3rd 1.38
4th 0.94
5th 0.72

FD 3.61

The 282 was available in some other cars with varying ratios. The other ratios for each individual gear are:
1st 3.77
2nd 2.19
4th 1.03
5th 0.81

FD 3.94

I'm not sure that the 282 case could even accept a 2.75 FD.

someone on the forum a while back was making 5spd gear sets in a long and short variety. think it was alimited time thing but i cant see why a machine shop cant just make one.

hmm, plenty of torque and only 21 mpg-you must be running a V8. In case anyone's interested, the exact ratios for a V6 282 are: 3.5000, 2.050000, 1.3750000, 0.942857142857, 0.72093023255, and the FD is 3.6111111111:1.

Yes, i'm running a 350 sbc with a 4 barrel carb and getrag 5 speed, 225-60-15 tires all around. I've observed 2450 rpm at 62 mph on my stock tachometer and speedometer, when cruising with my stock 97 Suburban alongside at 60 mph. I'm trying to get more economy out of it and make first gear more useable. I may have the later model early 2000's getrag with 3.94 final drive and .81 fifth gear. I didn't put this one in the car, so I don't know for sure.

Is there an I.D. tag or other way to verify what version getrag I have visually while sitting in the driveway (without opening it up)?

If I find I have the deeper final drive 3.94:1 with a .81 fifth gear ratio, changing to a stock final drive 3.61:1 with a .72 fifth gear ratio should help a lot. I could also gain some final drive ratio by switching to something like a taller 255-70-15 size rear tire for the added circumference. First gear would also be more useable with both changes, if I have the 3.94 final drive now.

Any more help on this one wouild be appreciated (+).

bump

IF you had the 3.6111 final and the 0.720930:1 fifth, 62 mph w/ 225/60-15 tires should give 2120 rpm. The most tire you're going to fit back there is a 255/60-15, NOT a 255/70-15.

quote Originally posted by gt7: Yes, i'm running a 350 sbc with a 4 barrel carb and getrag 5 speed, 225-60-15 tires all around. I've observed 2450 rpm at 62 mph on my stock tachometer and speedometer, when cruising with my stock 97 Suburban alongside at 60 mph. I'm trying to get more economy out of it and make first gear more useable. I may have the later model early 2000's getrag with 3.94 final drive and .81 fifth gear. I didn't put this one in the car, so I don't know for sure. Is there an I.D. tag or other way to verify what version getrag I have visually while sitting in the driveway (without opening it up)? If I find I have the deeper final drive 3.94:1 with a .81 fifth gear ratio, changing to a stock final drive 3.61:1 with a .72 fifth gear ratio should help a lot. I could also gain some final drive ratio by switching to something like a taller 255-70-15 size rear tire for the added circumference. First gear would also be more useable with both changes, if I have the 3.94 final drive now. Any more help on this one wouild be appreciated (+). bump

Assuming your speedo and tach are accurate, which is really assuming too much, you have the .81 5th and 3.61 FD. If the transmission is out of the car, just rotate the input shaft and count.

Do all 3.61 final drive transaxles have .72 fifth gear?
Do all 3.94 final drive transaxles have .81 fifth gear?
Is there an external test/inspection with the transaxle and engine in the car to determine which I have?

My math works out to say that I probably have a 3.94 final drive and a .81 fifth gear. Unless I find my tach to be way off. It has Archies tach conversion to go with the V-8 installation, according to the former owner. I am disregarding the speedometer as correct and I ran the car with my Suburban as a baseline.

This is my formula. It uses revolutions per minute for rpm, so it uses inches per mile because 60 miles per hour is the same as 1 mile per minute, or 5280 feet per minute, or 63360 inches per minute, for the sake of consistent units.

(63360 inches per mile) x (Ar = final drive ratio) x ( Tr = gear ratio) = (tire circumference in inches) x (rpm)

Using 3.94 as Ar, 80.52 as circumference, 2450 rpm, then Tr = .79

I used 80.52 for tire circumference because 225-60-15 works out to that and the tires actually measure a little over 25.625 tall.
Tires growing in height at speed could also make Tr = .81 (26.2125 tall is 82.07 circumference).
If tach is off and is actually 2500 rpm, using 3.94 as Ar, 80.52 as circumference, 2500 rpm, then Tr = .81

So I ask this:
Do all 3.61 final drive transaxles have .72 fifth gear?
Do all 3.94 final drive transaxles have .81 fifth gear?
Is there an external test/inspection with the transaxle and engine in the car to determine which I have?

bump

.

as far as I know the 3.94 final drive transaxles were Q4 bellhousing pattern
for the higher reving Q4s and will not bolt up to a V6 or duke

all the V6 pattern transaxles were 3.6 final drive
the lesser powered 4 bangers got the isusu transaxle

unsure about the 284 [rare DOHC V6] unit
or the later post 90s getrags
but they use a inside clutch slave/ hyd TOB

maybe the 6 speed is a cheaper answer then custom gears
or ask Getrag if they made other gear sets for use in other markets

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Question wonder and be wierd
are you kind?

I don't believe the BS that all muncies are geared the same. I use a muncie out of a 1988 Baretta for my V8 Fiero. The first two transmissions I used first gear was useless....maybe 10mph max. My current muncie first gear takes me up to 35mph. The only difference I noticed was the speedo gear had to be changed on my current transmission whereas it didn't on the last two.
Dave

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1987 GT (my toy-see above), 1987 GT (wife's toy), 1986 SE soon to be VR6, certified master technician/shop owner
www.njautobahn.com

[This message has been edited by bmwguru (edited 07-16-2008).]

quote Originally posted by gt7: Do all 3.61 final drive transaxles have .72 fifth gear? Do all 3.94 final drive transaxles have .81 fifth gear? Is there an external test/inspection with the transaxle and engine in the car to determine which I have? My math works out to say that I probably have a 3.94 final drive and a .81 fifth gear. Unless I find my tach to be way off. It has Archies tach conversion to go with the V-8 installation, according to the former owner. I am disregarding the speedometer as correct and I ran the car with my Suburban as a baseline. This is my formula. It uses revolutions per minute for rpm, so it uses inches per mile because 60 miles per hour is the same as 1 mile per minute, or 5280 feet per minute, or 63360 inches per minute, for the sake of consistent units. (63360 inches per mile) x (Ar = final drive ratio) x ( Tr = gear ratio) = (tire circumference in inches) x (rpm) Using 3.94 as Ar, 80.52 as circumference, 2450 rpm, then Tr = .79 I used 80.52 for tire circumference because 225-60-15 works out to that and the tires actually measure a little over 25.625 tall. Tires growing in height at speed could also make Tr = .81 (26.2125 tall is 82.07 circumference). If tach is off and is actually 2500 rpm, using 3.94 as Ar, 80.52 as circumference, 2500 rpm, then Tr = .81 So I ask this: Do all 3.61 final drive transaxles have .72 fifth gear? Do all 3.94 final drive transaxles have .81 fifth gear? Is there an external test/inspection with the transaxle and engine in the car to determine which I have?

No and no, to answer the first two questions. As for your calculations, modern radial tires grow very little at speed. What does happen however, is that effective rolling circumference is decreased by tire deflection, usually around 3-5%. Like I said, according to my calculations (which assume speedo and tach are accurate), you have a .81 5th and a 3.61 FD, which was found in 1991 Q4 Getrags.

[This message has been edited by FastIndyFiero (edited 07-16-2008).]

If tires grew much at speed, they'd wear around the center of the tread. This is usually seen only on overinfated tires, or the right rear of V8 Camaros without a limited-slip differential, or same with overinflated right rear tire.

What is the gear ratio of the Fiero Isuzu 5 speed versus the Fiero getrag? Would you get better gas mileage hooking the 2.8 to the Isuzu?

-Brian

Yes, And the perfect ratio is about 2.5 for me The isuzu is 2.48 I believe. Now if we could only make it stronger.....

There were two different sets of ratios for the 6 speed used in the G6 GT. The better set gives you a 0.62:1 sixth and a 3.55:1 final, plus the box is rated like 295 ft-lbs, much higher than the 282. The NSX trans is said to be strong, but the ratios are all wrong for you.