Final drive ratio and fuel economy

[milner351]

I agree, that's why I said earlier that trading MPG figures can be misleading. I've worked for two major auto companies now, and when we take test cars out for drivability testing, we calculate fuel economy based on the miles driven and the number of gallons required to fill the tank, hopefully filling the tank to the same point (like to the top of the filler neck as stated in the above post).

Well, you guys are all very encouraging with your numbers. I think perhaps I will invest in some slightly larger tires the next go 'round... my 235 85 16 still have lots of life left in them.

I already have no cat and no muffler, need a good down pipe, and some work on the intake side. Over time I'll put synthetic in the trans and axles.

Well, thanks gentleman, with all your comments, I'll stick with the 4.10s, and keep the speedo between 65 and 70. [img]/ubbthreads/images/graemlins/cool.gif[/img]

[Dr.Evil]

HEY.... You & I both like to run on the very bottom of the tank! I've put as much as 24-1/4 gal. in the front tank, but only 20-1/4 gal. in the rear. I've run as much as 395 miles on the little rear tank, and 470 on the front. I can easily make six days to work (120 mi round trip) and a little running around on weekends on around 38 gal, just over 19 MPG. I run 68-72 mph almost 100% interstate.

[agsF2501]

Well when I filled up it took 31gallons for both tanks. I flipped it when I normally do. I only put a little extra cause I had to hunt for a good diesel price so i was on E on the rear tank a little longer than usual. I figure if it got close I should always have a couple of gallons in the front tank. Front usually always take 14-16 gallons and rear usually takes the same amount or more. Probably due to the reason I explained. I think once I put in 34 gallons but that was tops. I will fill up in a couple of days and let you know how many gallons it took. I see too many fluctuations in diesel price right now to let it go that far into it and then have to fill up and X.XX just to make it home. Drive to work is like 140 round trip. Diesel on the way out is like 2.05 but get closer to austin and its like 2.15+ is what I saw this morning. I think I even saw a 2.21.

ART

[Quadzilla]

Art, you're killing me!! [img]/ubbthreads/images/graemlins/smile.gif[/img]

[ QUOTE ]
Diesel on the way out is like 2.05 but get closer to austin and its like 2.15+ is what I saw this morning. I think I even saw a 2.21.

[/ QUOTE ]

Here in Seattle, the best price I can find for diesel is $2.499, and that's down from the $2.579 I had to pay last week.
To find out how big my tanks actually are, I filled up both tanks, and drove on one until it started to sputter, then switched to the other one. Then, I stopped to fill up the empty tank, and topped it off to the top of the filler neck, which told me how much it would hold. Then I drove until the other tank sputtered, and switched back to the first tank. After filling that empty tank up to the top, I knew how much it would hold, and also how far I can drive after the needle touches the red. On the freeway, I can go another 60 miles after the needle touches the red.

[agsF2501]

[ QUOTE ]
Here in Seattle, the best price I can find for diesel is $2.499, and that's down from the $2.579 I had to pay last week.


[/ QUOTE ]


OOOUUUCCCHHH!!!!!!! [img]/ubbthreads/images/graemlins/vomit.gif[/img]. Wow that is high. I dont blame you guys for getting every last drop that you can. You know I think I may try that just once to build a baseline. Its just the place where I fill up is always jam packed, gas is also pretty cheap so I have to contend with those "guys". They also only have 2 diesel pumps other day I waited like 20 mins before I even got to the pump. Learned to fill up in the AM. Everyone is late for work and doesn't have time to stop, but in the PM forget about it. It's like candid camera out there. I feel your pain though. I am sure I will be paying those same prices before summer ends [img]/ubbthreads/images/graemlins/sick.gif[/img].

ART

[bullridin_fool]

with my truck cab and a half, dually 2wd, with 4.10's i've gotten 700 miles outa both tanks, this is runnin real low on fuel, i thought that was real good considering my tires are 215/85-16's [img]/ubbthreads/images/graemlins/eek.gif[/img]i just went with some biggins 235/85-16's [img]/ubbthreads/images/graemlins/biggrin.gif[/img], i'm hoping to gain a mpg or two. when you guy's talk about mileage pulling a trailer i almost laugh cuz my trailer empty weighs what your trailers weigh and that's before i put a tractor or two on it, but i don't get 20mpg pulling it either [img]/ubbthreads/images/graemlins/crazy.gif[/img]

[u2slow]

I was going to jump in with my poor economy (350km/tank) but my receipts show I haven't ever pumped in more than 26 gallons at a fillup [img]/ubbthreads/images/graemlins/confused.gif[/img]

I don't want to run a tank dry, but it sounds like I have at least 1/4 tank left in each when the needle is on 'E'. [img]/ubbthreads/images/graemlins/blush.gif[/img]

[black_smoke6.9]

Before the fuel prices jumped up over $2.00 a gal I was getting 16-17mpg driving 75 and 80 down the highway. Now I drive between 65 and 70 and I get anywhere from 17 to 19 mpg. That is with 3.55 gears, 33" tires chip in 50 hp setting. Nobody believes me when I tell them that i get around 18 mpg.

[Kevin Ferguson]

I swapped the R&Ps rather than the axles. It was a BUNCH of work....actually another word that starts with the same letter,
but we'll make things easy on the moderators!

Was it worth it? Well, it makes for a much happier sounding engine, First has become a fairly useful gear, and 4th is usable when towing at interstate speeds. Note that I live in NM, so speed limit is 75 on interstate, with traffic typically moving just a skosh over that (not a lot, though, 75-80 )

Unless you use the truck exclusivly for towing, 4.10 is just stupid-low gearing on the 5 sp. Note that a 5 sp with 3.55s cruises
at nearly the same rpm (~2400) as an auto with 4.10s.

Note that if your milage goes from 17 to 19 MPG, your range goes from
~650mi. to better than 725mi. In the desert southwest, that 75 miles of range can easily convert to choosing a station that is 10% or more cheaper per gallon.

For me there is no downside. If I towed more, drove a slushbox, or had to pay for the labor, or if I lived where the SL is lower, then I might reconsider.

[milner351]

Yea, I'd also considered buying the 3.55 front and rear gear sets and installing them, and selling the used 4.10 gear sets if anyone wanted them.

I think the bottom line is I probably don't drive the truck enough to make all the work worth it.

I think other modifications like replacing the down pipe and putting in a good intake system will be more satisfying.

For now, I still have to work on getting the title and plates... and finding a set of front bumper brackets for less than the dealer or ford network wants for them!

[SomeCarGuy]

The swap was worth about 2 MPG in my 97. Now getting 15 or so running 77 or so MPH. I think the radar thing on the side of the road showed the speedo is 2 MPH off so it really is 80 I think. 235 rubber

96 used to get 18-20 at 75-80 MPH. 22 or so running 60. 265 rubber