Just curiuos...

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Feb 18, 2005 | 08:56 PM

mwpierson

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Joined: Jul 2002

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From: Redding, CA

Just curiuos...

Back in late 2002 I bought a new 2002 F250... (3.73, v-10, 4x4, CrewCab, 4R100) and had plans to put 35s on and add a 4" lift. I also had plans to purchase a fairly large RV trailer (31' and roughly 9000# loaded). I wanted the lift to allow for 35s, I wanted the 35s for more ground clearance while in the mountains (not towing).

As some of you may recall from previous threads, I recently had the lift and 35s put on, had the speedo recalibrated and am no longer happy with the truck. The power is gone and I went from about 15mpg to 10mpg when not towing to about 6mpg when towing. If I want to get up that hill, I've got to drop it into 2nd and gas it hard. I am sure that a long trip with numerous hills would drop the mpg from 6 to 4 or so.

I know the 35s are causing my problems, but I’m curious, if I had purchased the diesel with the 373s, would I still have problems with loss of power and mileage with 35s?

Thanks,
Mike

Feb 18, 2005 | 09:12 PM

99f350sd

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Joined: May 2003

Posts: 9,303

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From: Lyndonville, Vermont

Yes the diesel would do better but you need a gear change and you will be back close to where you were. Maybe 4.30

Feb 19, 2005 | 09:25 AM

mwpierson

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From: Redding, CA

So, with 430s or 456s my power would return and could even be better. BUT, how close to my original mileage would I get? Would I be around 14/15mpg not towing and 10mpg with a load? Is there a calculator out there that will help me figure this stuff out?

Don't get me wrong, I understand that poor mileage is inherent to big trucks, especially when towing, but I think 6mpg is rediculous! haha

I guess I'm trying to figure out if switching to a diesel, before making any more mods and spending more money, will make me happier in the long run. If I could get closer to 15mpg towing with a diesel, even after the tires and regear, I think I'd do it. Again, BUT, if the mileage wouldn't be much better then now, I'd just stick my new gears in and be done.

Thanks,
Mike

Feb 19, 2005 | 09:34 AM

DS02F250

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From: Ventura County, CA

Mike,
Yeah, I'd be a bit "miffed" too with that kind of mpg. Gears would definitely help, but I for one would not go on record claiming you'll EVER get 14/15mpg (empty) and 10mpg (towing) with a V-10. Gears will be expensive (plan on ~ $1500 installed all said and done). How often you tow should determine whether to go with the 4.30's or 4.56's.

I came across this site not long ago. Check it out and see if it offers you any answers regarding the gearing...Click on "calculators" and go from there!
www.ring-pinion.com

Best,
Daryl

Last edited by DS02F250; Feb 19, 2005 at 09:38 AM.

Feb 19, 2005 | 10:01 AM

Kostiuk

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Joined: Oct 2003

Posts: 46

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From: Rockfield, KY

The gears would help your power problem but I think your mileage is gone. I don't see the gears improving your mileage. Generally lower gearing will hurt mileage a bit.

Feb 19, 2005 | 11:20 AM

Dave Sponaugle

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Joined: Nov 2003

Posts: 21,285

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From: Nutter Fort, WV

The gears will help the mileage because you will not have to drop to 2nd gear to go up the hill. But the increased height also increased the frontal area of the truck and the larger tires have more rolling resistance, so you will not get all the mileage back.

How much comes back will depend on how you drive the truck now compared to how you used to drive it.
The changed angles in the drive line also had some effect on your power transmission through the driveline.

Feb 19, 2005 | 11:46 AM

Lashlaroo

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Joined: Aug 2001

Posts: 389

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From: Georgia

Changing the gears can do some interesting things. Example, my 01 mustang had 3: 28? or : 08 I went with 4: 10. On the highway the car went from 26MPG to 27MPG @ 72mph. the time to go from 0 to 100 Mph got cut in half. Fuel mileage on that 0 to 100 also went down by half. anyway, If you are going to tow your trailer a lot, go with the 4.56's Less towing = 4.30 MPG???? 15 mpg towing with the diesel HAHA, not yet for me. closer to 12mpg. 18' flat bed and about 8K lbs. or 22' bayliner @ 4k both avg 12mpg. empty avg 17mpg. Now I dont have to slow down for the hills. And it's lots of fun in the mountains. passing all other trucks like there tied down. To see a dodge puff out a large black cloud as he floors it, you blow by and he's banging the dash with his fist! Makes the 5 thousand engine option worth every penny.