The kind of performance they are talking about is not better gas mileage and less engine noise and lower highway engine speeds.
3.73 gears "out-perform" 3.55's in terms of better launch and acceleration from dead stop to top end. Highway gas mileage decreases as the numbers get higher with 3.08 giving the highest mileage and 4.30 the worst. While the difference in gas mileage is significant between the 3.08 and the 3.73.. it is not so significant between the 3.55 and the 3.73, but the difference is performance is.
The 3.73 pumpkin they are recommending as being a more economical way to change gears also has an aluminum housing for less weight and heat retention, and it will actuall cost less to do the pumpkin swap than to buy the gears and pay the labor for the swap, 'cause putting diffential gears in is not something you want to do your self, unless you know what you are doing, but the pumpkin swap is a breeze...
Choices like this always depend on an individual's goals. How "unsluggish do you want it to be, compared to what down sides there may be." 3.55 is a good middle of the road choice, but will cost more to do... 3.73 is a more 'radical' change (but not real radical) cheaper to do (generally speaking), higher performing (as described above), but you will decrease your highway gas mileage, have a bit more engine noise when you drive and your engine will be running at higher rpm to attain the same speeds... also with the 3.73, you're top speed will be lower, but don't worry about that, you'll never see top speed anyway... without a chip, you won't see over 105mph, and anything over that is dangerous without some other upgrades....
'96 T-Bird LX 4.6L Alive & well & living in S. Florida
N/A: Renegade NPI heads/Comp Cams; OEM intake manifold; Bolt-ons
245 rwhp; 13.713 @ 99.35 (Commerce, GA - November 2003)
BLOWN: Renegade NPI heads; Renegade shortblock; Intercooled T-Trim; some other stuff
Pump Gas Numbers - 547 rwhp / 525 ft.lbs; Best Time - 11.388 @ 118.68 (Commerce, GA - November 2007)
Last edited by 96 GoldBird; 01-04-2004 at 02:51 AM.