gear ratio and gas milage
 

i make around 14-16 mpg here in nyc w/ stock 2.73's, mostly stop and go driving, no long highway crusin at high speeds. if i went to 3.73's, approx how much would my mpg go down? how bout 3.55's?

also, is $375 a good price for ford racing gears, lube, speedo, installed?

That is a good price and for around the street 3.55 gears will usually give you better mileage but you will see a drop on the freeway because of the rpm increase.

I've got 5.13:1's and burn about 1 gallon for every pass. 1/4 mile down, 1/4 mile back so that makes my mileage about 2-gallons per mile! :D

u saying 3.55's will increase city mpg or will just not decrease city mph as much as 3.73's???

speedytang is right. I went from 2.73s to 3.73s and city mileage didn't get any worse. Highway mileage dropped around 2-3 MPG due to RPMs.

Lets put it this way.... if you know how to drive without a lead foot, you can get the same gas milage out of the car. The car doesnt have to work as hard. With 3.73's, I lost maybe 1 mpg over the stock 3.08's, but sometimes, my gas mileage was the same. I cruise around at 70 mph but I dont accelerate like crazy when cross country-ing. Just easy cruisin. When I went AOD and the crazy OD gear, I was pulling 25 mpg with 3.73's, a carb and an AOD. That might have been a fluke for that trip (the air in maine was good that day) but usually I see 22 mpg with that combo in combined highway driving.

Now...around town, if you baby it, you'll actually GAIN mileage! Why? Cause of better torque multiplication, it will be easier for the motor to push the car around. Just accelerate like grandma and you'll be very pleasantly surprised. Gun it at every light and be prepared to shreik when you get to the gas station. ;)

With gas prices about 2.00 here is MA, I can see why you're concerned.

In my humble opinion.....3.55's just isnt enough to justify the cost (by the way, thats a DAMN good deal). Go at least 3.73 or maybe 4.10 (depending on tire height: 3.73 for 25.5's 4.10's for 26.6's).

thanks for the input everyone. crazypete, u always show me the way to the light! i never heard anyway say if u baby the car with the 3.73's u might gain mpg in the city, interesting idea and your theory makes sense. i have stock tire size 225/60 15 i believe, so i will probally go with 3.73 with my t-5. i have 4.30's in a 3 speed slap-stick challenger with a 340 engine, its a beast but gets like 4mpg around town!

gas is around $2.10 here and skyrocketing, and i gotta drive my stang in winter snow as well, hope the 3.73's dont hurt me too much. i figure the car is not really drivable in the the snow in stock form anyway!

I would go with 3.73 over 3.55. And that is a good deal. The only thing is when you get them installed, you can't keep from getting on it from the light. Especially when you get road rage like me. I went from the weenie 2.73's to 4.10's and I don't see a difference in gas consumption around town. I can say that it was like taking 5th out of the tranny. I can take off in second and put it in 5th at 40mph. Of course, the 351 helps that. It tachs about 2100 at 55mph. The analyzer on this site says I would be taching 2000 with a 26"tire. So it is accurate.

yeah, gonna go with 3.73's. a friend had it done at the same shop for $375 and he said the gears whine. is that b/c they didnt do the shims right? the same guy said he will do it for me for $100 labor and i give him the parts. i figure that will cost under $300, better deal to me.........

Yeah, they whine cause the backlash isn't properly set (shims). I have seen some that whine and all it took was tightening of the pinion nut (crush sleeve) to get it to stop. My fms 4.10 gears whine but they only have about 150 miles on them. I am gonna drive it a little more and see if it quietens up. If not, I guess I will be back into it again. Backlash was set at .009 and it had a good pattern on it too.