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I've been doing a little reading up on 3:54 gears for my Dually. My Buddie has a 99 24V Sport 2WD with them, his truck averages about 22-23 MPG towing a small 6X12 trailer that he uses for work purposes. I'm trying to get my Dually to the 20MPG mark driving empty on the hwy, I've got a best of 17.3 with 4:10's so fare.


I've got planes for a Upgraded tranny and maybe a Super B this summer if everything go's well? I'm thinking with a turbo and a good tranny, with the extra power and torque getting put down to the wheels, I'd be able to pull my 20' enclosed trailer threw the mountains of CO with little problems? I'd love to be able to cruse at 70 MPH at 1800 RPM's :thumbsup I was looking at a gear vendors double overdrive, but it's just to much cash! I'd rather spend the $$ on a tranny :thud:
 

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3.54's

3.54's are good for most everything. If i towed a huge trailer everyday the 4.10's would be my choice. a cummins and a stout tranny will pull anything you can hook onto. at that point the brakes and frame become question. sometimes empty on the freeway I wish I had a double overdrive. the last time I drove my dads truck (03 3500 3.73's 6 speed) we had a load of hay at 17500 lbs. had to drop down to 5th gear on I-25 but no problems with the cruise set at 60. I guess in a perfect world we would have the best of both worlds, towing and freeway gears. ??? any thoughts:woot:
 

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I've got 3.73s in my truck,but with the taller than stock tires,I'm effectively running 3.59s

I do have alot more power than you,but have no problems towing 11,000lbs.

If you bump up the power the 3.55s would be fine IMO.
 

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i had 3:55's in a 96 2500 . it was fine on the highway empty but i would have liked to have had a lower gear for pulling in the hills . IMO 3:73 gears are the best all around . if you need the lower gearing for pulling but , also need a higher gear for on the road an overdrive would be about the only way to accomplish both .
 

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I run 4.10 and 3.73's on my trucks. The3.73 is a great choice, I get plus 22 empty, and I can squeak it up to 25 if i really try. The truck when loaded, (usually in excess of 22K GCVW) has a yearly loaded average of 14.3 mpg with 3.73 and 13.8 mpg with 4.10's that is a big difference when you are running 150K plus a year. My 06 just truned 2 in ampril, and is just under 350K.

changing the ring and pinion gears is not too bad, and can be done for less than a few hundred bucks. (4X2)
 

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gears

I agree 3.73 are the way to go, I have an 08 6.7 auto 4x4 dually with only 3000 miles on it and getting 16 empty, have a new weekend warrior 40 foot fifth wheel, I only hauled once so far in dead stop traffic of course, so cant tell you what I am getting towing yet
 

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I had 3.54's in my 98.5 and 99 and towed everything from 17 ft TT's to 18k 5th wheels and never had an issue. I would love to have 3.54's in my Mega.
 

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I had 3.54 gears in mine put in 3.73s and detroit locker i think 3.73s are a great choice.:thumbsup
 

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I am calling B.S. on 22-23 while pulling even a 6x10. you can't compete with story telling.

most of the comments are from 6spds. If you pull over 8k you will not be happy with 3.54. I had both 4.10 and 3.54, my nv5600 (.72)is not far off from your 47re(.69) in final drive.

you will have to swap both axles. the rear will require a 3.73 thick ringed gear or a change of carrier for 3.54. the rear will cost $800 in parts, $1200 with carrier. I expect the front drive will be lower (never priced it out)

I was lucky and found a guy who wanted my 4.10 for his 3.54. Now cruising is nice, but loaded there is nothing better than the 4.10. for $1500-2000 more you could get an aux trans. or you could buy enough fuel to take you almost 4000 miles if you chose to do nothing.

With a dually and 4wd, you should expect 19-20 if you stay below 65
 

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I,m going to have to call BS on that as well. I have an 06 3500 dually automatic and pull a 40' Cyclone toy hauler and get 19 empty and 8 loaded. I usually get 12-13 pulling my 20' flats boat. With all the torque these engines have could you gear it up even higher to where you could run 70 mph at 2000-2200 rpm in drive with the OD off to pull heavy loads and really get some good mpg running empty at say 1500 rpm's in OD, or is there some reason that would not work?
 

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I have pull a 7500 lb. (loaded with car, tools, and supplies) open car trailer for the last 2 years a with a basically stock (except for airbox) 01 4X4 with 3.54s and the 5-speed manual. It has been perfectly fine pulling this load, but I don't get anywhere near that kind of fuel mileage. I get 14-15 mpg towing this load.
 
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