4.10s vs 3.73s vs 3.55s
 

I bought my first CTD last August. 1-ton dually 6-speed, 4.10.

Had a 1-ton Ford dually for pulling trailers as a work vehicle a couple of years before. Didnt like the ford aspect, loved having the duals... so I had to get one with a Cummins in it. The truck is/will be used my grain farm. Will probably be worked hardest during the spring for a couple of months pulling 1600 ga fertilizer tanks (bumper pull). These tanks gross anywhere from 16,000 - 20, 000lbs loaded.

That said, when I bought the truck I liked the 6-speed transmission... but I screwed up and didnt pay attention to the gear ratio before I drove off the lot. (too excited about my first CTD i guess ) It has 4.10s. Its too slow and I think uses too much fuel for me the rest of the year. According to my on-board calc, Im averaging 15 -16 mpg.

I am considering trading the truck in for one with 3.55s (maybe .73s)... is this a mistake given the pulling expectations I have for the truck. I would really like to have another 6-speed, does dodge make a 6-speed with 3.55s?

Also what do you guys know about this transmission cooling thing in the towing package? Assuming it is probably a necessity for pulling the fertilizer tanks. We have done this task with a '97 F-250 since we got it... and in my opinion its all but wrecked now with 120K miles on it because of the tank pulling.... These cummins engines last so long, I dont want the rest of my truck to fall apart before the engine goes...

What do you guys think? Thanks for the opinions..

I think with that kind of wieght, you'd better stick with the 4.10 gear. Forget about the fact that you are grossly over loading the max capacity of the truck with that kind of wieght. What is the tougue wieght of the trailer? Sounds like a fifth wheel hitch or gooseneck would be in order for 16 -20 Klbs.

15 -16 mpg sounds about right, if you had an auto you'd be down with me at 13-14 mpg.:p

You didnt specify but are you towing the tank around on the road/freeway? If so you might want the 4.10's but if your only tooling around the farm with all that wieght then I would go for the fuel miser gears for the street.

4.10 @ 20,000# is pretty good if you ask me. Is it a new truck? You didn't mention.

Up until 02 it was 3.55 or 4.10. 03+ is 3.73 or 4.10.

I tow 13,000 with 3.54 gears, no problem. That is a lotta weight for a bumper-pull, and I don't have a clue what a towing package has to do with cooling a 6-speed, the auto's have improved cooling in a tow package, but I have never seen it on a manual.

Tom

stick with the 4.10s... i dont know about the G/M i have 4.10s and i get 4mpg better than frriends with 3.53s it just sucks now cause i run out of rpms on the drag strip im probably stepping down to 3.73s but with a 6 speed, no lift and stock tires. i dont think you would have a problem stepping down. second i dont know if what you are referring to is similar to where im from but you arent on the highway... u could use low range..

Thanks for the replies...

The truck I have now is an '02.

We pull these tanks on county highways... no freeway driving. (Max 30-35mph)Im not sure if we would be able to get away towing these tanks in high range or not... Now that I think of it we always pulled with the ford in 4L. I guess if I did that I could get away with 3.73s.

I was unsure about the trans cooling thing... I could very well just be in the automatics, I saw it while looking at a couple trucks on autotrader.

Im confused with a couple responses....maybe you guys can shed some light....

How is it that an automatic, or a truck with 3.5s, gets worse fuel mileage than a manual with 4.10s....?

Improved fuel mileage is the primary reason for me trading the truck... I just assumed a truck with faster gears ==> lower running RPM ==> Improved fuel mileage.

My truck has 3.54's and I still get 20mpg cruising 70 on the freeway. My roommate with a 6 spd and 3.54's get's 13-14.

Actually Blue your effective gear ratio is higher than 3.54. Probably more like 3.08 or so. One thing to look at is RPM's at the same speed. The other varible is many people report vastly different fuel mileages based on which version of software loaded into the computer. Some guys report big changes when thye get reflashes. Just some more food for thought.

lukem86,

I would not worry about buying 3.73 in a new truck you will get better fuel mileage over the 4.10 gears. Weight with a cummins is not a problem with any gear ratio... The only time that I heard of where you could overload a drive train with a Cummins, was with a 1500 rpm stall speed torque converter (racing only), but in your case you would not have a problem in the high side of the current 6 speeds. 1st gear would be great to start the tanks rolling and then you will find that you have a 500 rpm split between each gear. I pull that kind of weight around during the summers and have no problems pulling highway speeds with a 6 spd and 3.73 ratio. I really think that 4.10 rears are unneccesary when you have the kind of torque and hp found in the Cummins. Gas rigs used lower ratios because of the lack of low end torque found in gas engines they had a harder time getting the load to simply roll away from a stop.

Yes, thats right. Up until '02 your gear choices where 3.54 or 4.10. '03 and up offers 3.73 and 4.10 gear ratio's. As for the milage being different between auto and manual, the manual usually gets better milage because it takes more power to turn an auto transmision than it does a manual transmision. The same rule of thumb applies to 4x4 verses 4x2. The later getting better milage since there is no transfer case to go through and no front drive gear to turn. But strange thing is, like others have pointed out, some trucks are getting great milage and some are not, no matter what gear ratio they have. I dont think anyone can tell you why either.

Just thinking after I already posted, but I'm only guessing if your going to loose money by trading in your truck for a different one, since thats never a profitable move. If the losses you might sustain are anywhere close to a couple of thousand just to attain a simple lower gear ratio for possible better fuel milage than why dont you go for the best of both worlds and have a gear splitter installed on you current truck? You would get the highway gears your looking for and even more towing gears. Plus even your reverse is spit, too. Just an idea.

I specifically got the 4.10's with an auto.
The new auto has a higher overdrive ratio than the new 6 sp. therefore reducing rpms @ 70 mph by about 1200 rpms.
I only tow 3000 lb daily and 6000lb occasionaly, but I wanted to put a larger diameter tire on my rig and then have the computer reflashed to correct the speedo.
You may check the RV/Towing forum to see what those guys say.

Fyi I get 17+ mpg with or without 3000lb trailer and I've only got 5000 miles on my truck now! :D

Just live with the 4.10s. The money you'd lose trading in or swapping gears will buy a lot of fuel.

I personally ordered the tallest gears available because I knew the 1st was a granny. You can always downshift a trans if your rear end is too tall, but you can't make the 4.10 taller in OD!

If you can't get a load moving with a NV5600's 1st gear and a mildly bombed Cummins hooked to a 3.55 axles, then you have MUCH bigger problems than a gear ratio.

It's much cheaper IMHO to add HP to improve towing than it is to gear down. NOt to mention better MPG.

JLH

KATOOM--

Interesting you brought up losing money on the trade.... I just got off the phone with the dealer I bought the truck from. Looks like I would take about a $6000 dollar hickey on the trade, and I have only put on 6k miles since I bought it.

Do you have more information about gear splitters? Where to get one? Estimated cost?

I had originally thought about this type of thing but really didnt know it existed for a pickup.

If you have more info, I would like to hear about it...

Thanks