I have a 04 3500 dually with a 410 ring gear I have talked to my local ring and pinion shop to see about changing from the 410 to either the 373 or they may be able to swap to a 342 any thoughts on this I have the 6 spd manual and don't pull a trailer to often looking for better fuel mileage was wondering if the mileage in the long run will be worth the 1500.00 for the swap that is for both front and rear diffs

 

tire size? year of truck? tranny od ratio? amount of weight you pull? highway speed? with a trailer highway speeds? without a trailer cruising rpm range you want to achieve that will fit bith with an d without a trailer? 1800 seems to be the sweet spot. i set mine up for 1700 rpm in OD at 60-65 mph and 1900-2000 rpm in OD at 75 mph seems to serve both worlds really well for me that is. I love my 315's with 3.73's and a nv5600.
s85s wouldnt be bad either

over gearing is bad under gearing can in some instances be detrimental. changing just ot save gas isnt worth it most the time. but if you do pursue changing your gears make sure you analyse those above questions. ive seen 3.42's a g56 and 285's serve as an awesome combo for mileage and towing yet others will say 4.10s and a nv5600 with stock rubber is the way to go . shoot 3.54's on my 12v dodge would beat any 24v with 4.10s equally equipted and towing yet others will tell you differently so you will be the final decision maker. remember but each truck is different so give us some details then with that info we might be able to give you more insight into whats worked for us.

 

Lots of guys with 2nd gens and 3:54's say they're good gears for mileage running empty and still tow good even on grades. I don't tow much with the little truck but the OTR tractors I drive are all 3:55's pulling some 7 and 8% grades passing other loaded trucks with no complaints from me at all. If you've got 3:73's and put 285's on it puts your ratio at about 3:50 or so. Tire size change would be the best/easiest way to get the gears right but his options there are probably limited with DRW. I'd look at a tire swap before doing gears. 3:42 seems a little too tall unless your tires are stock or smaller of course he's not towing much so maybe it won't matter. Plenty of folks on here running way taller than that, like "lincoln towncar ratios", with the 37" tires "I can use 1st gear" and still towing. Probably not much fun on grades though..

 

I am running stock tires at the moment and as I said I really don't pull a big trailer 16ft finding tires is a pain in the *** and I can get the swap done for 1500.00 for the both diffs I have thought about going to a taller tire in the 19.5 range but at that it is still way higher then the swap

 

this truck is 04 dually stock tires nv5600 tranny with 4.10 R&P I getting about 15.8 on the mpg but think that changing out the diffs theat I could get into the 20 range maybe I am wrong

 

i have some 3.73 if u want to swap

 

If you are only doing it for mileage don't waste your money. The only difference is when you are running empty at high speeds and that is not a big percentage of the time. If you are really that worried about mileage just slow down a bit and get a real difference at no cost. Slowing down not only slows the engine but it greatly reduces the wind resistance and that is the big benefit.

When you're towing in the mountains the higher gearing will make you drop a gear to get back to the RPM you were at with the 4.10s.


John

 

well i have 2 trucks 01 3500 dually 4:10s average 14 mpg towing 3000. my 00 2500 3.55s gets 17 i saw 22.7 mpg straight hwy at 70-80 never have i seen higher than 20 on the 3500 full tank of fuel 55 mile per hr it was a test did . i am considering swaping to the higher gears when you have higher horsepower it compansates.

 

I like 373 with stock tires. If you are thinking gears to help fuel mileage you should look in some other directions. You could spend your money on exhaust, and other mods with better results. I was pulling a 50ft 3 car hauler @ 33,000 lbs with no problems in 6th gear and still getting 9-13 mpg. With no trailer, 20-23 MPG.