4.10 vs 3.55

[f-two-fiddy]

I just put the first 500 miles on my 3.55's. I'll never go back to 4.10's. I saved 1/4 tank of fuel on the first day. Another 1/4 tank today.

235 mile round trip on Wed. Another 200 round trip today.

I don't tow. But I am usually loaded with 1600 lb's +

 

[david85]

A gear swap should be planned based on what the most common driving conditions are if fuel economy is the main concern. Most of my driving is at 70 MPH and up, so thats why I went with the gearing I have. Others might spend more time on slower highways (50-60 MPH instead of 70+) and in that case, 3.08s are not the bost choice unless you have an older transmission without overdrive.

I know guys that can get 20+ MPG with 4.10 gears (overdrive tranny) but thats keeping the RPM in the sweet spot and driving very gently (cruising no higher than 55MPH).

After all the modding with my truck, this is what I think is a good guideline for economy running empty:

50 MPH : 1500 RPM

60 MPH : 1600 RPM

70 MPH : 1800-2000 RPM

For towing, add up to 500 RPM to those depending on the load. With a turbocharger, 300 extra RPM should be enough for towing for the same effect.

Even 2000 RPM can still be fairly economical when running empty and it seems to be a good compromise overall for MPGs at highway speeds.

If you spend a lot of time in the city, than thats where 4.10s can be good for economy.

As far as gearing meaning more or less power....

As I said earlier, gearing has no effect on power delivered to the road and once you are in the powerband, accelleration is the same after you are half way through 1st gear. However, cruise RPM will be different, and thats where some careful planning is in order to get the most out of any potential gear swap in terms of MPGs.

 

[freebird01]

A gear swap should be planned based on what the most common driving conditions are if fuel economy is the main concern. Most of my driving is at 70 MPH and up, so thats why I went with the gearing I have. Others might spend more time on slower highways (50-60 MPH instead of 70+) and in that case, 3.08s are not the bost choice unless you have an older transmission without overdrive.

I know guys that can get 20+ MPG with 4.10 gears (overdrive tranny) but thats keeping the RPM in the sweet spot and driving very gently (cruising no higher than 55MPH).

After all the modding with my truck, this is what I think is a good guideline for economy running empty:

50 MPH : 1500 RPM

60 MPH : 1600 RPM

70 MPH : 1800-2000 RPM

For towing, add up to 500 RPM to those depending on the load. With a turbocharger, 300 extra RPM should be enough for towing for the same effect.

Even 2000 RPM can still be fairly economical when running empty and it seems to be a good compromise overall for MPGs at highway speeds.

If you spend a lot of time in the city, than thats where 4.10s can be good for economy.

As far as gearing meaning more or less power....

As I said earlier, gearing has no effect on power delivered to the road and once you are in the powerband, accelleration is the same after you are half way through 1st gear. However, cruise RPM will be different, and thats where some careful planning is in order to get the most out of any potential gear swap in terms of MPGs.

is it flat where your getting your 20+ milage???

Around here just driving back and forth to work (appx 7-8 miles @ 55-60 1500-1600 rpm semi flat) the best ive gotten is 18.8 mpg. and thats with a 7.3 idi w/ banks SW2 kit (wastegated) 3.55 gears and a ZF 5spd on stock rubber ext cab F250 4x4

When towing if its around here and in the hills the best i can get with my 16' 10k trailer haulin my suzuki samurai (about 5000# appx combined) is 14-15mpg and a trip to NC loaded with parts...tools...camping gear and 3 people (appx 8000#) on mostly flat highways runnin 55-60mph in 4th gear was between 11-12mpg

i can see hittin over 20mpg in a reg cab 2wd idi...

 

[RKOCH]

As I said earlier, gearing has no effect on power delivered to the road and once you are in the powerband, accelleration is the same after you are half way through 1st gear. However, cruise RPM will be different, and thats where some careful planning is in order to get the most out of any potential gear swap in terms of MPGs.

Absolutely untrue!!! The gear ratio has a direct effect on power delivered to the rear wheels and have the dyno sheets to prove it. The torqure mutiplycation factor if directly determinded by transmission and rear axle ratio. You will get going faster with a 4.10 compared to a 3.55 and when you get to the powerband the amount of power delivered to the road is a direct multification of the rear axle ratio. If you have 100 hp with a 3.55 and 100 hp with a 4.10 the 4.10 will deliver more torque and hp to the road period without lugging the engine.

My duelly has 4.88 gears a c-6 trans and 30 inch tires on it. I run the Interstate all the time in the 65ish range but found nothing that it will not move. Personally I go for power than fuel mileage.

 

[kcw12]

I have a friend with a 72 chevy and 3.08s (yes 3.08s) and pull a trailer everyday with 4-9000 pounds on it. His general reponse is. SHIFT for gods sake. push in the clutch and grab another gear and hammer her down.

 

[h2odrx]

So how much difference is there in fuel from 4.10 to 3.55?

 

[92F350CC]

Did you ever end up getting your truck on a dyno, RKOCH?

 

[Cat_Rebel]

You can run a high gear (3.08) with a stick but it sure ain't easy on an auto & I wouldn't do it.

 

[david85]

is it flat where your getting your 20+ milage???

Around here just driving back and forth to work (appx 7-8 miles @ 55-60 1500-1600 rpm semi flat) the best ive gotten is 18.8 mpg. and thats with a 7.3 idi w/ banks SW2 kit (wastegated) 3.55 gears and a ZF 5spd on stock rubber ext cab F250 4x4

When towing if its around here and in the hills the best i can get with my 16' 10k trailer haulin my suzuki samurai (about 5000# appx combined) is 14-15mpg and a trip to NC loaded with parts...tools...camping gear and 3 people (appx 8000#) on mostly flat highways runnin 55-60mph in 4th gear was between 11-12mpg

i can see hittin over 20mpg in a reg cab 2wd idi...

Actually no, its not flat at all. Most of the hills are 2-5% with one single hill that is about 8%. Two hills that I dreaded when my truck was still N/A are a good 2 kilometers long and 5% steady. But there are no portions that are completely flat.

For towing, I'm usually moving only an extra 2000lbs (see my gallery for pics) so the only real drag is wind resistance and at the same speeds I see 15 MPG average. This has been a windy summer so that kept my average below what it could have been, on rare calm days I have done 22 MPG. 20+ MPG numbers are running almost completely empty. My data was averaged over the latter half of this summer. The trip I took was the exact same 200 mile route each time.

With a trip only 8 miles long, the warm up time could be what is taking your MPGs down. No real fix for that unless you feel like using the block heater, or letting it idle and warm up, but its not really going to save you much unless you are making your own electricity or something. I think on longer trips of 20 miles or more, it is possible for you to see 20 MPG with the speeds you are driving at. Have you tried opening up the air intake?

Both my C6 and now E4OD transmissions is holding up just fine with 3.08s. Its simply a matter of using a lower gear to compensate in order to keep the RPMs up when more power is needed. The low stall torque converter does a good job of compensating for the tall gearing at low speeds. Haven't done a 0-60 test since all the latest upgrades, but I can usually leave traffic behind without reaching the floor.

 

[RLDSL]

Actually no, its not flat at all. Most of the hills are 2-5% with one single hill that is about 8%. Two hills that I dreaded when my truck was still N/A are a good 2 kilometers long and 5% steady. But there are no portions that are completely flat.

For towing, I'm usually moving only an extra 2000lbs (see my gallery for pics) so the only real drag is wind resistance and at the same speeds I see 15 MPG average. This has been a windy summer so that kept my average below what it could have been, on rare calm days I have done 22 MPG. 20+ MPG numbers are running almost completely empty. My data was averaged over the latter half of this summer. The trip I took was the exact same 200 mile route each time.

With a trip only 8 miles long, the warm up time could be what is taking your MPGs down. No real fix for that unless you feel like using the block heater, or letting it idle and warm up, but its not really going to save you much unless you are making your own electricity or something. I think on longer trips of 20 miles or more, it is possible for you to see 20 MPG with the speeds you are driving at. Have you tried opening up the air intake?

Both my C6 and now E4OD transmissions is holding up just fine with 3.08s. Its simply a matter of using a lower gear to compensate in order to keep the RPMs up when more power is needed. The low stall torque converter does a good job of compensating for the tall gearing at low speeds. Haven't done a 0-60 test since all the latest upgrades, but I can usually leave traffic behind without reaching the floor.

I notice you are north of the border, are those mileage figures adjusted for US gallons, or are they for imperial gallons?

 

[david85]

I notice you are north of the border, are those mileage figures adjusted for US gallons, or are they for imperial gallons?

3.78L gallons

 

[freebird01]

Actually no, its not flat at all. Most of the hills are 2-5% with one single hill that is about 8%. Two hills that I dreaded when my truck was still N/A are a good 2 kilometers long and 5% steady. But there are no portions that are completely flat.

For towing, I'm usually moving only an extra 2000lbs (see my gallery for pics) so the only real drag is wind resistance and at the same speeds I see 15 MPG average. This has been a windy summer so that kept my average below what it could have been, on rare calm days I have done 22 MPG. 20+ MPG numbers are running almost completely empty. My data was averaged over the latter half of this summer. The trip I took was the exact same 200 mile route each time.

With a trip only 8 miles long, the warm up time could be what is taking your MPGs down. No real fix for that unless you feel like using the block heater, or letting it idle and warm up, but its not really going to save you much unless you are making your own electricity or something. I think on longer trips of 20 miles or more, it is possible for you to see 20 MPG with the speeds you are driving at. Have you tried opening up the air intake?

Both my C6 and now E4OD transmissions is holding up just fine with 3.08s. Its simply a matter of using a lower gear to compensate in order to keep the RPMs up when more power is needed. The low stall torque converter does a good job of compensating for the tall gearing at low speeds. Haven't done a 0-60 test since all the latest upgrades, but I can usually leave traffic behind without reaching the floor.

i have thought about it...right now the truck has the air cleaner/snorkle setup that comes with the banks turbo kit. looked aweful restrictive to me...not to mention it still has a muffler and 3" pipe out the back. been waiting to replace the exhaust with straight 3 or 4" and get rid of the muffler

 

[RKOCH]

Did you ever end up getting your truck on a dyno, RKOCH?

Not my big one no, the wheel trac was too wide for his rollers the tires kept catching the sides of the rack. He said he would bring the wide one in OCT to that pull.

 

[david85]

i have thought about it...right now the truck has the air cleaner/snorkle setup that comes with the banks turbo kit. looked aweful restrictive to me...not to mention it still has a muffler and 3" pipe out the back. been waiting to replace the exhaust with straight 3 or 4" and get rid of the muffler

I have a 3" pipe with muffler too. At relatively low RPMs and light load a larger pipe won't really make much difference in terms of fuel economy. A cold air intake Might help slightly though. Air from the grill of the truck instead of under the hood is colder and therfore a little more dense.

 

[freebird01]

the banck air cleans does just that...its got a dual snorkle so to speak that sits on top of the radiator support...ill see if i can get a pic