Change from 4.10 to 3.73?

[Rhondasway]

My stepdad has an early '03 3500 6sp that he hauls a very big camper with. He has 4. 10's and only gets about 11mpg. He hauled the same camper on a non-dual Ford diesel with 3. 73's and got 13. Would changing his current diff to 3. 73's improve his mileage? I assume this is also not a very pricey exchange?

Any input is appreciated; I gotta keep him happy he got a Cummins!

 

[DonTX]

Different strokes for different folks I guess, but I looked until I found a 3:54 geared truck, nothing else would I even consider. It gets 22. 9 mpg empty consistently. I feel it is rather stupid to scream along the highway waaaaaay above your maximum torque rpm or decent mileage rpm. I have hauled around the heaviest truck camper made, and am about to depart pulling a 35ft double slide fifth wheel. My truck runs well at 1750 rpm at 65mph, just loafs along and only sips fuel.

That is the reason they put gear shifters and automatic transmissions in trucks, so you can have a screamer when you need it for a hill or passing, not all the time droning down the highway.

 

[CumminsBu]

If he runs stock size tire the 3:73 gear will help alot, because with the 6 speed and 4:10 and stock tires running at 65mph he is turning 2200RPM. If you can get the RPM below 2000RPM you should see an improvement.

 

[DMcGalliard]

Improved MPG with 3.73 vs 4.1.

:-lafI have a 05,4x4,3500,3. 73, I don't think the switch will make much difference, I get about 12MPG with the way I drive, 72mph, If I drive 60mph I get 14MPH. we were in the mountains at 55 and I got 15. My camper is a 1181 that weights 6000lbs. For the my Teton I would like to have the 4. 1. Bottom line is how you drive, how fast, the wind load is the major problem with MPG not the final drive.

Dave Mc

 

[JHardwick]

I've wrestled with this as well ... ... ... . I just can't bring myself to believe that the gear swap will pay for it'self.



I'm loaded all the time and spend a lot of miles on back roads throughout the country ... ... ..... plus screaming down the interstate @2300-2500RPM.

 

[tgrfan2]

My stepdad has an early '03 3500 6sp that he hauls a very big camper with. He has 4. 10's and only gets about 11mpg. He hauled the same camper on a non-dual Ford diesel with 3. 73's and got 13. Would changing his current diff to 3. 73's improve his mileage? I assume this is also not a very pricey exchange?

Any input is appreciated; I gotta keep him happy he got a Cummins!

Two friends of mine had nearly identical fivers and 2003 HO 48res. One had the 4. 10s and the other 3. 73s. They have towed together several times and the 3. 73 truck consistently got 1. 5 mpg more towing and had no trouble keeping up in the Smokes. The 3. 73 owner towed with the 4. 10 truck once and said he wouldn't have 4. 10s. He has a 68rfe with 3. 73s now and still says the same thing.

Changing over is another matter. How long he keeps the truck and how much he tows plus finding a competent mechanic to swap it out. I had the "best" Dana 70 mechanic at a dealership here rebuild mine. It had a whine from the get go that I could hear over my 12V! When it tore up the carriers again the rear end shop that did the work said what he did was fine but that it was just a few thousandths "tight" causing the whine. That whine would be very annoying on a common rail!

I would say if it ain't broke don't "fix" it.

 

[HeberRam]

Ronda, I am assuming he is running stock tires... . Have him put on a leveling kit and run some 33's this will lower his gear ratio and increase his mileage. I have an auto and tow a 12K 5th wheel and I would kill for 4:10's.

 

[Bob V]

I think the fact the the Ford is a SRW has more to do with the better MPG than the gear ratio (it also most likely has taller tires). Like has been said before, a slightly taller tire would be a lot cheeper than a gear change, just remember to take the larger tire into account when figuring MPG. I think someengine mods will give the best results,ie, smarty on the towing/milege setting.

 

[CRuth]

It may pay off, but it is a pretty pricey swap.

 

[Rhondasway]

Ronda, I am assuming he is running stock tires... . Have him put on a leveling kit and run some 33's this will lower his gear ratio and increase his mileage. I have an auto and tow a 12K 5th wheel and I would kill for 4:10's.

Hey pal! Long time, no hear! Howaya?



Thanks for the input everyone; keep it coming! Does anyone know a ballpark price for gear change? Hard to believe that 6 new tires would cost less... Heber, you want to buy the 4:10's if we do swap 'em?

We are also considering engine mods, if appropriate. Everyone feel free to chime in here about that too. Nothing elaborate or expensive, though, I don't want him out-performing the Princess! :-laf

 

[Forrest Nearing]

it's a pricey swap unless you just swap out complete rears...



if I were doing a gear swap, I would seriously consider the new 3. 5x gear avail for the AAM axles. It'd be great w/ his 6sp

 

[klaybus]

Rhonda,

With parts in hand Randys R&P quoted me $840 for labor only. Last Monday I walked outta there for about $850 in parts. Thats swapping out my 3. 5s for 4. 10s. I would speculate your looking at about $1800-$1900 for a 4wd installed if my prices are any reflection of what they get for it.



Clay

 

[DonTX]

I used to think that duallies took fuel myself, but I seem to be getting as good of MPG (or better) with my dually as any single rear wheel does.

I think the fact the the Ford is a SRW has more to do with the better MPG than the gear ratio (it also most likely has taller tires). Like has been said before, a slightly taller tire would be a lot cheeper than a gear change, just remember to take the larger tire into account when figuring MPG. I think someengine mods will give the best results,ie, smarty on the towing/milege setting.

 

[JHardwick]

2003 HO 48res. One had the 4. 10s and the other 3. 73s.

I know my mind is slipping, but you might want to go back and revisit the available options at that time. That just doesn't sound right.

 

[tgrfan2]

What doesn't sound right about that? Both were bought in March or April and the 48re was only available with the HO at that time.

 

[JHardwick]

I don't, just doesn't sound right.



When I ordered mine, you had to get the NV5600 to get the HO.



Or did they still have the 47re early '03 model year, and then reliease the HO with 48re a little later?



I told you my mind was slipping!

 

[CUMMINZ]

I think you will never pay for the difference. Big mistake... But I am a 4. 10 kinda guy.

 

[RWorth]

'03 and 48re

I don't, just doesn't sound right.

When I ordered mine, you had to get the NV5600 to get the HO.

Or did they still have the 47re early '03 model year, and then reliease the HO with 48re a little later?

I told you my mind was slipping!

Late model 2003 could be specified with an HO motor with the 48re auto. When I started searching for agen 3 truck this was what I was loking at and I did compare the VIN of the trucks and what the numbers on the Cummins motor ID tag.

Roger

 

[clem]

I myself love my 4:10, 10-11 towing 19 empty. I would not change,but if want to get 22mph and keep the hill climbing power. I would go for a Gear Vendor Gear Splitter then you could have the best of both. Start looking at Camping World no Change is cheap.

 

[HeberRam]

Hey pal! Long time, no hear! Howaya?



Thanks for the input everyone; keep it coming! Does anyone know a ballpark price for gear change? Hard to believe that 6 new tires would cost less... Heber, you want to buy the 4:10's if we do swap 'em?

We are also considering engine mods, if appropriate. Everyone feel free to chime in here about that too. Nothing elaborate or expensive, though, I don't want him out-performing the Princess! :-laf

Ronda, it's been awhile. In Utah the swap would be $1300-1600 depending where you go. This would include parts and labor on a 4X4. If I were to supply the parts, they would not warrant the job. When you swap gears, it has to be done by a professional as there is too much that can go wrong due to improper shimming of pinion gears and carrier bearings etc. On a 4X4 it is a big job. I sugguested changing out tires when the orginal ones wear out thus not big cost difference. If things for some reason change you can always go back to stock and still have the 4:10 ratio. Changing gears is something you do not want to do again. Just my thoughts.