I was curious, since when one puts a big aftermarket stall on their truck it usually means alot worst gas mileage. If you have 4.10s, since the shift is alot quicker does it mean its gonna help you in city driving? Cus I know my truck with 3.73s and 3400 stall killed me in the city. My friend has a 3200 stall and 4.10s and hasnt even seen a difference.

 

short answer is, it depends on the converter more than anything, a looser converter is gonna be more fun to drive whereas a tighter converter will be better than stock but not to loose for everyday driving. it also depends on the size of the converter. for example, the stock converter is 12"-13" (give or take) and most aftermarkets are 10.5" or 9.5 ", the 9.5" is from a F-Body or corvette and will be a much looser converter but will help the car launch hard as ***** and spool at higher rpms. i have a 3200RPM Vig 9.5" and if i nail it around 50 you can hear the converter spooling and the motor screamin at RPM wheras a 10.5" 2800rpm will feel more like stock under all drving conditions cause its not as loose as the higher stall smaller converter which inherently has less area on the vanes and rotors for the fluid to contact and the stator will be built looser for a higher stall but a moodier daily driver.

So i guess what i am saying is that discussing gas mileage and performance in the same breath is like discussing AA in a liquor store

 

well both have all similar specs, except mine is a 3400 and his a 3200. Both are TCI.

 

Depends on city versus highway for the gears. For the converter - absolutely not. High stalling converters always hurt economy. Torque multiplication with fluid makes a lot of heat and that heat has to come from somewhere. Once the converter locks up above 40 (or whatever) MPH it's set to, the converter efficiency and type doesn't matter.

As for the gears, higher RPM on the highway uses more gas for the simple reason that the engine and transmission have to overcome more friction for the same amount of forward motion.
On city streets it takes less throttle to get moving from a stop, and less torque multiplication in the converter for the same amount of forward acceleration.

So, high stall torque converter - NO
Higher ratio gears, highway - NO
Higher ratio gears, city stop and go - YES

 

Thats not necissarily true, because the engine has its "range of optimum efficiency" when everything is working together and you have enough power being made to overcome almost anything without a downshift or pedal adjustment. for LS1 based motors, if i recall correctly, the optimum rpm range is somewhere in the neighborhood of 2600-2800 rpms which happens to be almost exactly 70mph with a 30" tire, a set of 4.10's and the .70 OD of the 4l60e transmission. i say this only because for example my truck has 3.23 gears from the factory, and i can average high teens to low twenties on the highway for gas mileage but i have to cruise 80-85mph if i drop to 70-75mph my mileage drops to the mid to low teens and thats not good. so in essence the efficiency of an engine comes from its piston speed measured in FPS which can then be translated into RPM's at the crank which can then be calculated down relatively accuratley assuming a light throttle condition with a locked converter. because an unlocked converters efficiency is all over the map because of fluid viscosity changes among other things. also the parasitic drag on the engine parts and the transmission parts and the rear-end components. hell i bet with the proper tools and enough free time one could argue that the inertial forces exerted by the spinning U-joints are causing unnecessary with currents and the design of the U-Joint needs to be refined to incorporate aerodynamics and inertial loads. So what i am saying is, there are thousands of factors that impact mileage, and most modifications will not help mileage (barring a few).

Soapbox off

 

ok i know wut u mean by at the end of your post....BUT, wut i wanna know is how 4.10s and higher stall do in the city...is it better than 3.73s and a higher stall in the city???

 

yes, it is

 

Higher Ratio Gears - Yes.
High-Stall Converter - No, never. (They are a lot more fun though.)

If your focus is miles per gallon, leave the drivetrain parts alone. Run the tires at maximum rated pressure, drive slowly, and try to keep RPM under 3500 all the time. Get a soft bed cover. Even lowering it will help marginally.

These drivetrain modifications we are talking about here are for better performance not economy.

 

Lowering it actually saved me tons!! When I had the 2/4 drop I saw 22 mpg and when I raised it back up I saw maximum 20 mpg.

 

I know with the 4.10's in my truck and stock converter if I keep the rpm's on the interstate around 2k then I can see 18.5 to 19 mpg. If I bump it up to about 2400 or so it drops to 15.5 to 16 mpg.