Good Sam Club Open Roads Forum: F250 3.73 to 4.30 axle ratio
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 > F250 3.73 to 4.30 axle ratio

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LanceRKeys

Amarillo, TX

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Posted: 05/30/20 07:20am Link  |  Quote  |  Print  |  Notify Moderator

What are you pulling now and how does your truck do? I agree with the above, pull with it first then decide if you want to change.

carlislefamily2011

usa

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Posted: 05/30/20 07:25am Link  |  Quote  |  Print  |  Notify Moderator

I pull a 2018 Palomino Pum 32rkts. We are still 5th wheel shopping, just needing advice on what type of dry weight and hitch weight to shop for after possibly upgrading our axle ratio. Thanks...

valhalla360

No paticular place.

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Posted: 05/30/20 11:40am Link  |  Quote  |  Print  |  Notify Moderator

BenK wrote:

Mark the drive shaft or tape a length of string on the drive shaft

Roll the vehicle one tire valve rotation

Then count the number of sting wraps on the drive shaft, or have someone count the chaulk marks on the drive shaft

Whole turns is the first, whole number of the diff ration...3 turns...4 turns, etc equal 3.xx or 4.xx

Fraction of a string wrap will be the fractional portion of the diff ration...3/4 turn, then X.73, etc

Remember to remove the string

Got some folks yelling at me on another forum...guess they didn't remember to remove the string...


Or just look up the code on the door jam.

Really unless you are using that last bit of tow rating (ie: you aren't exceeding the tow rating with the 3.73), it won't make much difference. I think it's 6 speed transmission in 2017, so it will just pick a different gear and result in roughly the same overall gear ratio from crank shaft to wheel.


Tammy & Mike
Ford F250 V10
2008 Copper Canyon 5er
Catalac Catamaran 34'
Full Time spliting time between boat and 5er


Old-Biscuit

Verde Valley

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Posted: 05/30/20 12:04pm Link  |  Quote  |  Print  |  Notify Moderator

Regardless of Gear Ratio the Rear Axle Weight Rating will not change


Is it time for your medication or mine?


2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
2007 HitchHiker II 32.5 UKTG 2000W Xantex Inverter
On the Road Debt Free April '07
Off the road still Debt Free Jan. '14

BenK

SF BayArea

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Posted: 05/30/20 01:07pm Link  |  Quote  |  Print  |  Notify Moderator

Most diff gear ratios are about 10% from the one higher and lower

So the torque multiplication is around 10% more or less

A 3.73 is about 10% lower (numerically) than a 4.1...therefore about 10% less torque multiplication

Truck labels only tell what it left the factory with. Some folks like me, have changed the gear set to a different gear ratio

The string method doesn't care what the label says...


-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

rjstractor

Maple Valley, WA

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Posted: 05/30/20 06:56pm Link  |  Quote  |  Print  |  Notify Moderator

BenK wrote:

Most diff gear ratios are about 10% from the one higher and lower

So the torque multiplication is around 10% more or less

A 3.73 is about 10% lower (numerically) than a 4.1...therefore about 10% less torque multiplication

Truck labels only tell what it left the factory with. Some folks like me, have changed the gear set to a different gear ratio

The string method doesn't care what the label says...


3 year old truck that the guy probably bought new so the door label is probably accurate. The OP didn't ask how to determine his axle ratio anyway. The string method would be invaluable if there were no other way to find out, but observing engine rpm at 60 mph (on GPS, not speedo) and doing a little math is probably more accurate. And if one doesn't want to do math there are many online calculators that do the math for them.

Grit dog

Black Diamond, WA

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Posted: 05/31/20 11:02am Link  |  Quote  |  Print  |  Notify Moderator

As usual, a whole page not pertinent to the question and we're only on page 2.


"Yes Sir, Oct 10 1888, Those poor school children froze to death in their tracks. They did not even find them until Spring. Especially hard hit were the ones who had to trek uphill to school both ways, with no shoes." -Bert A.

Grit dog

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Posted: 06/01/20 02:24pm Link  |  Quote  |  Print  |  Notify Moderator

carlislefamily2011 wrote:

I pull a 2018 Palomino Pum 32rkts. We are still 5th wheel shopping, just needing advice on what type of dry weight and hitch weight to shop for after possibly upgrading our axle ratio. Thanks...


Whatever the towing guide says.....
'Nother person who only hears what they want to hear.....^

Retired JSO

North Georgia Mountains

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Posted: 06/01/20 04:32pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

Get the trailer first as 3.73 will pull just fine a few times. Gears do not increase payload, just increases the combined weight rating. Cost to swap is $900 to $1,500.

He has a 4X4 which will be closer to $4500.





rhagfo

Portland, OR

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Posted: 06/01/20 06:53pm Link  |  Quote  |  Print  |  Notify Moderator

carlislefamily2011 wrote:

I pull a 2018 Palomino Pum 32rkts. We are still 5th wheel shopping, just needing advice on what type of dry weight and hitch weight to shop for after possibly upgrading our axle ratio. Thanks...

So that TT has a 9,600# GVWR and is 35’ long.
We are currently towing a 32’ 5er mid profile that based on my calculations currently has a 2,800# pin weight and 10,600# on the axles so about 13,400# 5er.
Unless you look at 1/2 ton 5ers to get a reasonable pin weight for your axle.
We looking at 36’ to 40’ 5ers with pins that will be in the 3,600# to 4,000# range.


Russ & Paula the Beagle Belle.
2016 Ram Laramie 3500 Aisin DRW 4X4 Long bed.
2005 Copper Canyon 293 FWSLS, 32' GVWR 12,360#

"Visit and Enjoy Oregon State Parks"


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