whiteNblack95

if you are doing a lot of highway miles your gears are hurting you. and o2 sensor will help, if you dont already have one, invest in an intake. try cleaning your fuel system and your maf.

enix187

the idea that 3.73 gears aren't hurting gas mileage is idiotic, I'm not saying its worth it to swap out the gears but low gears cause high rpms at cruise speeds has the kid even said whether or not he has an aod or a 5 speed. The biggest difference in mileage would be made by his driving and o2 sensors, what kind've mileage are you getting anyway, it may not get any better.

67mustang302

3.73's aren't going to hurt mileage enough to matter. What, 0.5mpg? Maybe 1mpg? How you drive has a lot to do with it, as well as how well tuned the engine is.

AdderMk2

people dont seem to understand its a matter of efficientcy. Having the car spining 2500RPM's at 65mph will allow the engine to work easier than the same speed, but only 1900-2000 rpm's.

But what the hell do I know... It's not like ive taken the EFI University courses or anything...

67mustang302

When I swapped to the TKO 600, I still had the 3.00 gear I was running from the Toploader before I did the gear swap. 5th gear on the freeway going from 3.00 gears to 3.55's my mileage seemed to actually get slightly better, maybe by about 1-2mpg. But it certainly didn't get worse. As it is now I only turn about 2k rpm on the freeway....makes me wish I'd gone with the .82 o/d instead of the .64 o/d.

enix187

So adder what you're saying is I can leave my car in fourth at 65mph and have better mileage? How about 80mph? With forward thinking like this why don't we all put toploader 4 speeds in our cars? I'm not saying that the gears are the problem, but saying that they don't drop mileage at all is still moronic. The biggest difference will probably be found in how he drives the car, past a good tune and working sensors not driving like an *** 24/7 makes the biggest difference

AdderMk2

you are completely overthinking the situation here. Do you have access to a vac gauge?

If you do, connect it and run your car for one full tank of gas. Keep an eye on that vac gauge, and do everything you can to keep it as low in the vac scale as possible. You will see an increase in mileage.

With low gear ratios, 2.73/3.08, in top gear, your RPM's end up being quite low, and you will "lug" the engine. You will have to put more pressure on the throttle to maintain your speeds. The reason for this is that you fall too far off the low end of the torque scale. If you can get the rpm's up to a point where you are making more torque, but not fully up in the HP (higher end) side of the power curve, the car will be more efficient. I wish I was home right now, so I could go out and show you the differences between load levels, RPM, and injector pulse width...

maybe then you would understand. Bottom line, stop arguing, you are wrong!

AdderMk2

what im trying to get to is the efficientcy of the engine at certain RPM's.

Your car will get better gas mileage at 70mph in 5th gear, than it would at 55mph in the same gear. Even though you are using the same gears, the engine isnt working as hard at the higher RPM.

Now ofcourse, stepping up to 5.13's would go beyond this as you would have surpassed a point of diminishing returns.anything beyond a 3.90, and in certain cases, a 4.10... will begin to reach that point.

67mustang302

Keep in mind, newer production vehicles cruise on the highway at anywhere from 2,000-3,000rpm. The smaller the engine, the higher the rpm it's set up to cruise at.

everett

3.73 will improve city mileage. Just keep it in a good state of tune and keep your foot out of it