Changing gear ratio

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Jan 15, 2009 | 09:39 AM

JohnG3

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Changing gear ratio

I have a 2004 F250 SD Excab, 2WD with a V-10 and 3.73 rear end. I tow a 5th wheel trailer and am at max GVWR and almost 500# over GCVWR. I read the post that said the only difference between the F250 and F350 springs/suspension is the size of the block, so I'm not too worried about the GVWR. I'm also going to remove the receiver hitch. The owner's manual says that this truck has a GCVWR of 17000# with the current rear end and a GCVWR of 20000# with 4.30 rear end.

Now the issue. The dealer says the only ratio avaible for my truck is the 4.10. If I went with that 4.10, would it increase my GVWR to about the mid point between 17000 and 20000? Is the rear end with the 4.30 a different design/size? Is there a chart or formula that I can use to figure the new GCVWR?

Thanks in advance

John

Jan 15, 2009 | 12:20 PM

Toreador_Diesel

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Joined: Sep 2003

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From: Houston, Texas

Don't go to the dealer if you want to do something like regear your truck. The only reason they told you 4.10 was the max was because that's what they had in stock and really wanted to sell you on it. It's also funny how from 1999-2004 a small number of V10 trucks shipped with 4.30 gears and not one was shipped with 4.10. It wasn't until the 2005 MY that they shipped V10s with 4.10 gears; before that it was either 3.73 or 4.30.

Get a second opinion and go to a reputable gear shop, they'll tell you a completely different story. You'll spend between $700 and maybe $1000, but they'll get you the right kit and the right gears the first time.

It's also not a matter of it increasing the GCVWR or the GVWR; with 4.30 gears the powertrain doesn't have to work as hard to pull a heavy, or in your case, heavier load. With 3.73s, your truck really has to work to get and keep that trailer moving, especially up hills; which can lead to burnt trans or worse.

If you plan on keeping the stock size tires or going up to 285s, 4.30 gears will work wonders for you and your V10.

Check out some of these posts from X_Hemi_Guy

https://www.ford-trucks.com/forums/s...74&postcount=6

https://www.ford-trucks.com/forums/s...02&postcount=4

Jan 15, 2009 | 03:40 PM

ReAX

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From: Central Florida

I concur. You will not see much difference, if any in mileage between 4.10 and 4.30. I calculated mine to just over 4.11 with stock tires and I almost wish I had gone lower. Find a shop who specializes in drive line work, they can get gears fairly cheap and do the install for around $1200 an axle. I think I have about $2400 in my gear swap, I did Motive 4.56, Ford LS clutches, RP oil and a mag hytech rear cover.

Jan 15, 2009 | 06:28 PM

JohnG3

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Thanks. Its great to hear advice from those who been there, done that. Only reason for the dealer is we have the 6 year/60000 mile warranty and I wanted to keep that intact.

Jan 15, 2009 | 07:11 PM

1975StroppeBaja

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From: WV

Quote:

Originally Posted by JohnG3

Thanks. Its great to hear advice from those who been there, done that. Only reason for the dealer is we have the 6 year/60000 mile warranty and I wanted to keep that intact.

conman3300 had a post a few weeks ago saying that his local Ford dealer quoted about the same money ReAX said so you should be spend a reasonable amount and be able to keep your warranty.

https://www.ford-trucks.com/forums/8...-is-crazy.html

Jan 15, 2009 | 07:19 PM

mwsF250

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Joined: Jun 2008

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From: Wayyy NoCal, USA

I'll also jump on the "go deeper" bandwagon. How deep?

Tell us:
What size tires are you planning to use?
What is your "normal" cruising speed? 50? 60? 70?

Based on those, you'll get several suggestions.