Gear Ration & MPG

[danielhv]

Ok, so my brother swapped out the rear end on the 87GT with another one that has 4.30's in it... My concern is MPG at this point. I know, this isn't a prius, but I drive back and forth to Dallas quite a bit and for now, need to be somewhat conservative. I havent made the trip in this car yet, but its coming up. Couple of questions:

What was the stock ratio on the 87 5speeds?

What kind of MPG can I expect with the 4.30's?

What kind of MPG could I expect with the stock ratio?

I know some of those questions will vary with driving habbits, but I'm talking about on the highway, 70 - 75 mph for 5 hours... Just looking for some ballpark figures to see if its really worth putting rearend with the stock ratio back in...

[TRAXX]

Couple of questions:

What was the stock ratio on the 87 5speeds? 2.73 (3.08 optional)

What kind of MPG can I expect with the 4.30's? Not sure, but 4.30s in 5th will be roughly equivalent to 2.73s in 4th.


What kind of MPG could I expect with the stock ratio?
3-4 mpg better than what it currently does..but Im only guessing

responses above

[SEB]

Not good! Prolly 15 hwy & 9 town

[Damnittsteve]

t5 or aod?

[danielhv]

t5 or aod?

T5

[majorownage]

23 mpg with 4.30s in a boat. My UDPs really helped.

[hotrod66stang]

23 mpg with 4.30s.

I doubt that, but I guess it's possible. I have '90 notch, 5-speed with 3.08s, and the highest MPG I've gotten is 25.

[SEB]

I doubt that, but I guess it's possible. I have '90 notch, 5-speed with 3.08s, and the highest MPG I've gotten is 25.

x2 I hve 3.08s in my hatch & i see right at that also

[majorownage]

I doubt that, but I guess it's possible. I have '90 notch, 5-speed with 3.08s, and the highest MPG I've gotten is 25.

4.6L sir

[Vertnut]

4.6L sir

...and AOD? I have 3.73's w/5sp in a 5.0 and I get 23 on the highway if I drive 65mph and act right. I just never do...

[majorownage]

...and AOD? I have 3.73's w/5sp in a 5.0 and I get 23 on the highway if I drive 65mph and act right. I just never do...

4r70w; much the same.

[Rotortrash]

I doubt that, but I guess it's possible. I have '90 notch, 5-speed with 3.08s, and the highest MPG I've gotten is 25.

This is about what I see in my 92 with the T5 and 3.08's as well. My 93 got 27-28 with 2.73's, if it was all highway driving.

[91CoupeMike]

I get around 25 in my coupe with 3.73s, I got around 23 with 2.73s. I have a heavy foot so the lower gear just bogged me down more.

4.30s in a foxbody isnt going to be worth a damn, you're going to be ~2500rpm
In 5th at 60mph and closer to 3k at 80mph, which will suck fuel and wear stuff out faster. t5 5th gear is a shitbox at high rpm.

When I had 2.73s 4th to 5th was butter, went to 3.73s and it went to shit, acts like a sycro went to shit due to a gear swap, wtf?

[crapstang]

get 8.66s and 42" donk rims.

[danielhv]

I get around 25 in my coupe with 3.73s, I got around 23 with 2.73s. I have a heavy foot so the lower gear just bogged me down more.

4.30s in a foxbody isnt going to be worth a damn, you're going to be ~2500rpm
In 5th at 60mph and closer to 3k at 80mph, which will suck fuel and wear stuff out faster. t5 5th gear is a shitbox at high rpm.

When I had 2.73s 4th to 5th was butter, went to 3.73s and it went to shit, acts like a sycro went to shit due to a gear swap, wtf?

Is there going to be much difference if I drop down to 3.73's? I'm not sure how far I should go... Want decent mpg, decent longevity, but dont want to be bogged down as well...