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Discussion Starter #1
My question is has anyone done the change from 4:10 to 3:73 for the fuel mileage and if so do you need to have the computer reprogramed? And how much difference in pulling did you see, as i pull a 35 ft weekend warrior toy hauler?
 

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i would look at a Gear vendor over drive unit.....less money the a gear change

Dad ran one in his blue oval for 5 years and pulled a 40' 5er and he was 26+k combined weight

Scott
 

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I ran a Gear Vendors for years in my 460-powered Ford. Really durable, good to 1,200hp, pretty high GWV (can't remember what it is, but it's on the web site), quiet operation. Seems pricey when you see what Gear Vendors is asking for the setup, but it really is a top quality product.
 

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probably doesn't answer your question, but i went from 3.73's to 4.10's because i already had the intent that i was going to raise my truck. it worked out well. because i still experience to good MPG's with my setup even though i have some 325/60/20's on( about 15-19.5mpg's)

Im sure if your staying with your stock size wheels and tires and move down to 3.73's i would imagine that you will save more fuel, also depending on what your doing and how your doing it. good luck.

It cost me about $1500 to do the gearing.:thumbsup

and yes i would recommend doing the updating the computer as far as gearing. the dealer could do that for your free though. I know my dealer would. but if you have a chip, it'll be free.
 

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OK, a few questions form a heavy hauler. How much does your combination weigh? What kind of fuel mileage are you now getting both loaded and empty? What is your RPM at 60 MPH towing? In reality going from 4.10 to 3.73 will gain you maybe 1MPG. You are not talking a large percentage change there, so the gains will be minimal at best.
 

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OK, a few questions form a heavy hauler. How much does your combination weigh? What kind of fuel mileage are you now getting both loaded and empty? What is your RPM at 60 MPH towing? In reality going from 4.10 to 3.73 will gain you maybe 1MPG. You are not talking a large percentage change there, so the gains will be minimal at best.
Agreed but I think larger OD tires will also add to that MPG difference. I'm about ready to drop 2K on a regear because I hate running almost redline keeping up with highway traffic. I sure as hell won't drive through Kansas at 50mph just so I can keep my 19 MPG. 75 mph drops it down to 14 mpg....go Dodge, some smart engineering there.
 

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if your running a stock tire with 4.10 gears you can just move up one and be almost at 3.73. I have not measured the tires on my truck but on the Ramcharger stockers are about 29" with 4.10 gears and 33's it put it around 3.60. With 31's it was around 3.84

Hope this helps
Chris
 

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3.73's

I Have The 3.73 Gears I Took Out Of My Truck At 20,000 Miles (switched To 3.42 Because Of High Crusing Rpm With 6-spd) If Anybody Needs These Pm Me.
 

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Discussion Starter #10
i am running 35's on with the 6speed automatic, and you figure the 4x4 quad cab is around 10 thousand pounds and the 35 ft trailer is 19 thousand full loaded. empty no trailer i get 13mpg at 70 and loaded i can get aroun 11 at 55. so i really think the 3.73 would help out greatly in my case, what do you think?
 

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I have had the 3:73's in my last 3 trucks. Before that I had the 3:55's in the other 6. You have plenty of gear with 3:73's to tow a 18K trailer anywhere you need to go and you will save about 2 MPG doing it.
 

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i would just move up to some 31's - 33's. Less work...and hopefully you need new tires soon . Plus it will make your truck look more like a truck.

i always hated the way these big :butt: trucks look like with such small tires.

good luck.:thumbsup
 

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I have an '07 2500 4x4 Quad cab w/ 3.73 gears. I pull a 12Klb. 5th wheel toy hauler and wish I had 4.10. My mileage is 11 - 12 while towing (65 MPH). (My '06 5.9 w/ 4.10 gears got 14 - but it was a 2wd) We have a lot of rolling hills here and the trans seems to want to hunt a little going up hill. If it doesn't downshift, it will lose 7 - 10 mph. With the 4.10's in my '06, you could set the cruise a 68mph and it would never need to downshift and would never lose more than 1 - 2 mph. This set up seems to be struggling more. At 70 I'm turning right at 1700 RPM. With the 4.10 (yes, it was a different transmission too, but if you do the math, the final drive ratio is the same) I was turning about 2K RPM.

Having said all that, if you're intent on dropping down to 3.73, I'll swap with you....
 

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LSmith, are you using Tow/Haul? I find no gear hunting with my 68RE and I am pulling 18K
 

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Yes -- but the biggest frustration is the drop in speed. The "hunting" only happens when I'm not in cruise. I'll give it gas to maintain a speed and it will downshift for just a second then upshift again - and then the speed starts dropping again. In cruise control it just slows down.....
 

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You may have something wrong because mine doesn't drop like that or jump in and out of gear.
 

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Yeah, probably is something the matter. This thing runs like a V-6 gas motor -- but I don't have any codes!!!
 

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Len,

You have the AX flash??? I guess your running the 6.7 stock also???

I see so much about the gearing on this new 6.7 motor and with my own experience with my on truck, the 6.7's with the 6 speed manual seem to get better fuel mileage with the 3.73's and the 6.7's with the 6 speed auto do better with the 4.10's...

I would sure love to have a set of 4.10's for my truck with what I tow all the time...

I also have a really cool gear ratio and tire calculator program I found on-line. I use the bottom one that you can pick and plug the numbers in as you like. Gives you the RPM for what tire size gear ratio and the whole thing as you change from tire to tire size and/or gear ratio...


Engine RPM Calculator

Now for the final drive ratio on the tranny, if you have the 68RFE auto, your 5th gear OD is .81 and the 6th gear over drive number you plug in is .62!!! This program will figure the rest out for you and with either your 5th or 6th gear...

Edit: I forgot to mention that since I deleted and removed all the emission stuff and added the edge juice w/attitude, I have no problem towing anything. Even in 6th gear OD the truck just tows whatever, its the fuel mileage help I want the 4.10's for... Mainly from I get the same mileage towing in 5th or 6th gear. I don't feel this should be the case if I didn't need gearing help. I am running the 31.8" tires that are worn down to about 31 even right now.

I like the larger tires also, but I may try a set of smaller tires to help the gearing a little...
 

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Yes, I have the AX flash and the truck is stock (including 265/70-17 tires). I guess the thing that bothers me the most is this truck will lug all the way down to 1200 RPM before it will downshift by itself in tow/haul and 1000 RPM in normal mode. I don't know how ya'lls trucks run, but at 1000 to 1200 RPM, my truck is really sluggish-- towing or not. My 5.9 (2006 -- all stock) never dropped that low so I don't have an apples to apples comparison, but there is no way this truck has the guts that truck did. And the 5.9 did not have to downshift to maintain it's speed. the torque would hold it.

My '07 is on it's third turbo, the ECM has been replaced twice (in addition to all of the re-flases), the EGR replaced, all the sensors replaced at least once, and everything has been "cleaned" numerous times. You know, I don't really think I should have to spend a bunch of money on aftermarket parts to get this truck to operate at the same level as my previous truck. A modern diesel truck should not have to come with a list of do's and dont's -- don't idle, don't take short trips, run at high RPM's at least once a week to make sure the crap burns out of the catalyst -- this is ridicules. That kind of stuff would be okay for some specialty vehicle or a vintage truck, but not a present day, commercially available $45 - $50K truck. They've gone backwards 25 years....

Sorry for the rant -- and thanks for the calculator!
 

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Discussion Starter #20
Hey ranting is cool, everyones gotta do it. but to me sounds like maybe you have a lemon and with all the work you have had you more then qualify. i had to do that with my F350 and then i came over to dodge. i have the 2007 6.7l with the mp8 and edge juice stacked and i havent had any problem, but then i drive it like i stole it too. i have heard drive them easy and drive them like crazy. so maybe find that happy meduim or try the lemon law.
 
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