I just bought a 91 gt with an auto tranny and it has 3:73's in it. But i want to get better gas milleage out of the car. I had a 90 gt with a manual tranny and stock gears and i was getting 24 on the freeway and about 17 around town. What are the stock gears that come on a 91 aod, and what would you suggest i use to get good gas milleage and perhaps a lil better performance than the stock gears?
Gears??
- Thread starter Drago
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willys1
Active Member
Usually they had 2.73's.I just took them out of my 93lx aod.I was getting 18.4 around town,and low 20's highway.The gears only have 25,000 miles on them,let me know if you want em.Drago said:
T_5.0_N'works
New Member
willys1
Active Member
T_5.0_N'works
New Member
willys1 said:
I don't think 2.73's were equiped in every year, it came from factory with 3.08's, option or not, that is a stock gear.
willys1
Active Member
TrophyHead
15 Year Member
You could also get 3.27 in an auto as a option. Best thing to do is look at the driver's side door jam and get the axel code.
Are you getting really bad gas milage with the 3.73's? It could be something else like an oxygen sensor or coil or gas leak. Theres a ton of reasons why you can get bad gas milage. I'd pull codes and see what comes up before I pull the 3.73's out for stock ones. Yeah with 3.73's you will have worse gas milage than stock. But not that much worse. I would not go any lower than 3.27's. 3.27's are good for high supercharger applications also.
Are you getting really bad gas milage with the 3.73's? It could be something else like an oxygen sensor or coil or gas leak. Theres a ton of reasons why you can get bad gas milage. I'd pull codes and see what comes up before I pull the 3.73's out for stock ones. Yeah with 3.73's you will have worse gas milage than stock. But not that much worse. I would not go any lower than 3.27's. 3.27's are good for high supercharger applications also.
DTT92LX
New Member
my 92 came with 3.27s. not a bad gear but i'll upgrade to 3.73s in the future. My guess is you're gonna miss those 3.73s after a while!
Compared to my last mustang im getting bad gas mileage. I just drive freeway miles a quite often though and would like to be able to go a little faster and run less rpm's. With these 3:73's im running at like 2500rpm at 70mph, where my other stang was runnin about 85 at 2500rpm. Ill go ahead and pull some codes to see if anything else could be wrong, i just want a little bit better of a ride since i drive freeway miles more than i just race and drive around town.
huskerpower02
Member
You bought a mustang to worry about gas milage? 
j/k man....i was having the same questions.
-Drew
j/k man....i was having the same questions.
-Drew
TRWXXA
Member
Drago said:
2500rpm sounds a bit high for 3.73s at 70mph. What size tires do you have? 2600rpm gives me about 80mph (26" diameter tires). Is your speedo reading acurately? Mine's been checked with a calibrated radar.
3.55 rear end gears with 225 –60R15 tires
Cruse on the highway at 65 MPH in 5th gear
Engine RPM: 2057
Vehicle Speed: 65
1st gear
Engine RPM: 5200
Vehicle Speed: 34.
Rear End Gear: 3.55
2nd gear
Engine RPM: 5200
Vehicle Speed: 56.
Rear End Gear: 3.55
3rd gear
Engine RPM: 5200
Vehicle Speed: 83
Rear End Gear: 3.55
4th gear
Engine RPM: 5200
Vehicle Speed: 111
Rear End Gear: 3.55
3.73 rear end gears with 225 –60R15 tires
Cruse on the highway at 65 MPH in 5th gear
Engine RPM: 2162.
Vehicle Speed: 65
1st gear
Engine RPM: 5200
Vehicle Speed: 32.
Rear End Gear: 3.73
2nd gear
Engine RPM: 5200
Vehicle Speed: 53.
Rear End Gear: 3.73
3rd gear
Engine RPM: 5200
Vehicle Speed: 79
Rear End Gear: 3.73
4th gear
Engine RPM: 5200
Vehicle Speed: 106.
Rear End Gear: 3.73
Cruse on the highway at 65 MPH in 5th gear
Engine RPM: 2057
Vehicle Speed: 65
1st gear
Engine RPM: 5200
Vehicle Speed: 34.
Rear End Gear: 3.55
2nd gear
Engine RPM: 5200
Vehicle Speed: 56.
Rear End Gear: 3.55
3rd gear
Engine RPM: 5200
Vehicle Speed: 83
Rear End Gear: 3.55
4th gear
Engine RPM: 5200
Vehicle Speed: 111
Rear End Gear: 3.55
3.73 rear end gears with 225 –60R15 tires
Cruse on the highway at 65 MPH in 5th gear
Engine RPM: 2162.
Vehicle Speed: 65
1st gear
Engine RPM: 5200
Vehicle Speed: 32.
Rear End Gear: 3.73
2nd gear
Engine RPM: 5200
Vehicle Speed: 53.
Rear End Gear: 3.73
3rd gear
Engine RPM: 5200
Vehicle Speed: 79
Rear End Gear: 3.73
4th gear
Engine RPM: 5200
Vehicle Speed: 106.
Rear End Gear: 3.73
willys1
Active Member
I have 373's,an aod,and stock size tires,225/55/16,,,,At 70 mph Im at 2300 rpm... At 80 mph,Im at 2500 rpm.I have FMS shorty headers,stock h-pipe,and 3 chambered Flow Masters. At 70,and 80 mph,you cant even here the exhaust,it is whisper quiet!!! Not that,,,that is a good thing !!
Michael Yount
Mustang Master
If the speedo's off, your gas mileage calculations are off as well. What else is done to the car? I don't think the gear change alone is gonna make that much difference. You may get slightly better highway mileage, but the 3.73's probably help a bit with your around town mileage. If better mileage is all you're after, I think you'll be disappointed with a gear change. But I'd check out current running condition, and be sure your speedo/fuel mileage calcs are accurate before I changed the gears.
The car has cobra upper and lower intake, 70mm tb, 3:73's, fuel pressure regulator, and a computer chip, along with flowmasters. The tires are 225/50/16. But my 90 gt had a rebuilt engine .30 over, some head work done, an e303 cam, bbk shortys, new h pipe w/ hi flow cats and magna flows, 70mm tb, 73mm mass air, k&n of course, and 205/60/15, and stock gears, with that i was getting 17-18 town and 23-24 highway.
T_5.0_N'works
New Member
I think a good tune-up will go a long ways in gas mileage. Should do that before you dive into gear ratios.
willys1
Active Member
The 70mm TB is a bit much,a 65 will do just fine.As far as the gears,buy some taller tires and your rpm's will come down while driving on the highways!
