f250 gears

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Mar 11, 2005 | 04:01 PM

barry e

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f250 gears

hi, i have a '99 f250 4x4 auto with 3.73 gears & 285-75-16 mt bfg's ,i want to go to 4.30 but ,i have found a set of 4.56 cheap . is 4.56 to low ??? thanks barry

Mar 11, 2005 | 05:04 PM

jackofalltrades

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From: Lynden, WA.

The question is, Why would you want the 4.30's? 4.56:1 isn't much difference from them but a couple hundred rpm at freeway speeds. But the jump from the 3.73's to those gears is going to make it sound like your engine is singing a new tone. If your goal is larger tires, affecting the "final drive ratio" then doing the math, or looking at gear/tire size charts to put your rpm in the power ratio of your engine's output is the thing to do.

Mar 11, 2005 | 06:47 PM

barry e

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f250 gears

i'm wanting to make it tow better , stay in od on hills [ empty]. when towing 6000 to 10000 i have to run over 70 mph to keep in power band or the cruise will kick off at the slightest hill [od off] .

Mar 11, 2005 | 08:06 PM

NoMo

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From: OK

No signature and you don't say what engine you have...

If it's a PSD, I'd not go any 'lower' than 4.10s.
If it's a gasser, then the 4.56 would be OK.

Mar 11, 2005 | 08:25 PM

jello

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From: Terrace B.C. Canada

I used to have an old chevy w/4.88's and 38.5" tires.In the winter I would switch to 255/85/16 (33" tall).When it was in drive it was revving like it was in second.May want to think twice about the change.

Mar 11, 2005 | 08:52 PM

99f350sd

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From: Lyndonville, Vermont

I was wanting to go with the 4.30's in my 99 for more tow power. I have 4.10 now and I can't see how you go anywhere with those gears unless you have the v10. I have stock tires. I do 2k rpm in over drive at 60 mph 2.8k out of od. I wouldn't mine 2.5 k in od.

Dick

Mar 11, 2005 | 09:34 PM

barry e

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f250 gears

hi, it's a V10 . does any one have 4.56 gears & 285 75 16 's , what is your rpm at 70 mph ?? i don't want bigger tires. thanks barry

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Mar 17, 2005 | 01:40 PM

jackofalltrades

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From: Lynden, WA.

Barry, Check this out!

http://www.jeeptech.com/javaAps/gta.html

It's a little program that, if you give it all the ratios of your transmission, gear ratio in the differential, and the tire size, (height), then it'll tell you exactly what your RPM and Speed will be in any of the gears. This sounds just like what you need to make your best informed decision to keep your engine in the power band when you're hauling.

Hope it helps.