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Old Oct 12, 2010 | 08:36 PM
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rearend help

Ok, here goes another dumb post, sorry. I have a 94 f250 donar truck. It has the 351 gaser 5 speed and 3.55 gears, I think axle 39. My daily driver is a 96 f350 dually crew with auto, diesel, and 4.10LS, I think axle d4. I have read a thread on swapping the gears out between the two sterling rearend housings if they are the same, but I am not sure if my two are the same. I have numbers from he tags from the rearends if that will help. Just looking for sum expertise.
 
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Old Oct 12, 2010 | 08:54 PM
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Axle 39 is 3.55 open diff as long as no one changed it. I can't remember what size the ring gear is in a 350 dually but here pretty soon someone will chime in with the answer.
 
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Old Oct 13, 2010 | 09:27 AM
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the dualy and the srw should both be 10.25 sterling gen2's in those trucks. I'm not aware of them making a different dually axle for the 250's and 350's, but its always possible.
I don't think the d60 rears are full floaters, so if the axles are the same, then they are 10.25's

There is a bit more to it than just "swapping" the gears though I hope you know this before you proceed further.

If you are looking to tow with the 3.55's and a stock truck, I highly suggest against it.
But to each his own.
I dont want taller gears after driving these 4.10's.
Only thing I'll go to now is a gear vendors or a dual speed rear.
 
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Old Oct 13, 2010 | 09:36 AM
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They are both Sterling 10.25" ring gears.

3.55s are ok, but they don't tow like 4.10s. I know, I've towed with both.

If you want the best gear combo for rpm, fuel economy, and towing ability, get a 3.73 gear set.
 
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Old Oct 13, 2010 | 11:59 AM
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A BIG HELP

This is what I am looking for, thanx soo much. Yes I will be towing with this truck, 11k fifth wheel, but not that often. I was looking for a gear that would service daily driving and towing, had the donar truck and thought what the heck. I have towed the same load with a modded SD, but I think it has 3.73, and it did just fine, but it has stage 1's, dp tuner, exhaust, intake, etc. I plan to do the same mods with this OBS, just wanted to get the gearing and tranny up to snuff first. Still on the fence about the tranny, I like the auto, but the cost to have a good E4OD built is steep, but I would prolly be done with it once built. Thanx for the reply, info from experience is good, I take it all.
 
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Old Oct 13, 2010 | 12:19 PM
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If you run 3.55's with the mods you list (like I have pretty much) you will be able to tow fine. You see what I tow in my pic +-16k loaded. It does run best at 75+ pulling though with the high gear. 65 I usually run in drive, depends. 75 is still only 2050rpm in od with mine. Before I did my mods I thought about switching to 4.10's, now I'm glad I didn't. Someday I wouldn't mind having 3.73's for a couple hundred more rpms but not 4.10's.
 
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Old Oct 13, 2010 | 01:14 PM
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towing

If you run 3.55's with the mods you list (like I have pretty much) you will be able to tow fine. You see what I tow in my pic +-16k loaded. It does run best at 75+ pulling though with the high gear. 65 I usually run in drive, depends. 75 is still only 2050rpm in od with mine. Before I did my mods I thought about switching to 4.10's, now I'm glad I didn't. Someday I wouldn't mind having 3.73's for a couple hundred more rpms but not 4.10's.

So would you rather have 3.73? How does your truck pull? I know that a dumb question, but are you happy? I just don't want to throw alot of $ at this truck and then be disappointed. I don't pull my camper fast, but like to maintain the speed limit, and not hold up traffic, just a quirk I have, especially if its a Cummins waiten to go around, LOL.
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Old Oct 13, 2010 | 01:24 PM
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If you are taking the time to swap gearing, and you want to pull a load with it, I would reccomend using the 3.73s. you will be approx. 2000rpm at 70mph.

I assume you are 2wd, if so that makes it easy. I want 3.73s but I am 4wd, so that means I have to regear both axles $$$$$
 
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Old Oct 13, 2010 | 02:10 PM
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GEARS

ya, I'm 2wd dually. I guess I have to way it out, cuz rite now at 70 I'm runnin round 2300, assuming my speedo is correct. Don't throw rocks at me, but i have not towed with this truck yet to even know where the power is or If I even like the 4.10. I should go on a short run and see how it does, I may like it. Honstly I'm gettin round 14 mpg either on the highway, or runnin round town, which isn't too bad considering (dually with 4.10's). It just sounds worse than it is in the cab due to down pipe rubbing on everything it possibly can, even after repeated attempts to fix it, enough to make a preacher cuss!!!
 
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Old Oct 13, 2010 | 02:18 PM
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Your fuel mileage should improve with taller gears, and turning 2300 cruising will hurt mpgs, but the 4.10s get a load moving nicely.

I know from experience that 3.73s tow nicely. just my .02
 
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Old Oct 13, 2010 | 02:20 PM
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I would rather have 3.73's but my truck pulls the load fine now. It would just be better, pretty much ideal, with 3.73's.

Trust me, I don't hold up traffic.
 
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