3.73 or 4.10 with automatic and some towing?

[tschwab]

I know this has been discussed/argued on these boards numerouse times, but I am close to purchasing a new 2500 with the automatic, the wife will be driving it.



We do about 6 tows (about 400 miles each) per year and the 5th wheel logs in around 10k dry, should not be any heavier than 12k loaded. The truck would be a 2500 HO 325/600. (NO MOD's planned for this truck except the aFe Mega Cannon intake).



Leaning towards the 3. 73 for a couple of reasons.



Slightly better fuel economy (lower rpm = less fuel burned).

When towing, it is better on the transmission to have O/D off.

The majority of the driving will be around town.



Thoughts/Comments - PLEASE!

 

[SSage]

At what speed will you be pulling?



With 4. 10s on an auto dually, I need to pull at least 65 mph to get 2000 rpms. At 60 mph pulling over 12K the engine will lug on every hill, down to 1500 to 1600 rpm. The engine seems to like 2000 to 2300 rpm or 65 to 70 mph when pulling. Thats fast to me, I run the 48 RE and 4. 10s on a dually. Third gear gives me a bit too many rpms at 65 for my taste, the 3. 73 won't be much different. I think the 4. 10's are a good all around choice for the auto trucks. If your like me and prefer over 2000 rpm at 65 mph to advoid lugging below 1800 rpm, the 4. 10's make sense. 65 mph/2000 rpm is a nice towing speed for me, my trailer tires don't like much more.

 

[Wiredawg]

We went w/ 3:73s and Like it

We like the 3:73s on my wife's 03. She has 32K miles and is getting almost 23 mpg. The 3:73s w/ 17" tires act the same as 3:54s did w/ 16" tires. My wife is about 1975 rpms at 70 mph. As a daily driver, you can't beat the 3:73s.



I've towed about 10K lbs enclosed car hauler w/ it and it did fine in OD. We didn't go thru any serious grades.



No matter what you get, be sure to install boost, EGT and transmission temp gauges. You can't get cheaper security.



Wiredawg

 

[thejeepdude]

I've been mulling this over and over through my head and still can't make up my mind. One minute I'm 100% sure 3. 73 and a week later I'm thinkin 4. 10. I just ordered my 2005 and I ordered 3. 73. My thought is, I had 3. 55's in my '99 with less HP/TQ and towed my 8. 5'x20' enclosed car hauler full loaded up the sierra nevada mountains with my Jeep and 2 ATV's in it, and never had to slow down. I did unlock OD for a few of the steepest hills, but the RPM's weren't ridiculous. The new 48RE stays locked in 3rd, and the 3. 73 is a little better than the 3. 55, and with more power, I think I'll manage, even with bigger tires. I think it'll be worth it for the longer trips empty or over flat ground where the high gear will help MPG. OK, I just talked myself back into 100% sure I'd go with 3. 73.



If I change my mind later, I'll just swap the gears out myself for ~$500 and throw in a locker while I'm at it!

 

[PatrickCampbell]

If I did it again, I would get 4. 10s with auto, 3. 73 with 6spd. OD is fine for towing heavy and with 4. 10s you will have slightly higher RPMs, less lugging and much better acceleration.

 

[Sherman]

I know this has been discussed/argued on these boards numerouse times, but I am close to purchasing a new 2500 with the automatic, the wife will be driving it.



We do about 6 tows (about 400 miles each) per year and the 5th wheel logs in around 10k dry, should not be any heavier than 12k loaded. The truck would be a 2500 HO 325/600. (NO MOD's planned for this truck except the aFe Mega Cannon intake).



Leaning towards the 3. 73 for a couple of reasons.



Slightly better fuel economy (lower rpm = less fuel burned).

When towing, it is better on the transmission to have O/D off.

The majority of the driving will be around town.



Thoughts/Comments - PLEASE!

The auto will tow better with the 4. 10 overall,but for 2400mi/per year I would go with the 3. 73's and get better mpg as a daily driver.

 

[klenger]

The 3:73s w/ 17" tires act the same as 3:54s did w/ 16" tires.

I keep seeing the above statement quoted here, and would like to clarify as follows:



The first number of the tire size is the width. The 2nd number is the profile or ratio of width to height (rim to tread), and the 3rd number is the rim size.



For example, on my truck, I have 265/70R17 tires. They have a width of 264mm, height of . 7*265=185. 5mm (rim to tread). If you convert the 185. 5mm to inches, you get ~7. 3". Double the height, add in the rim size, and you have a 31. 61" tire diameter.



The tires I had on my 01. 5 were 265/75R16. Doing the same math, the tire diameter for them is 31. 65".



Therefore, the tire diameters of the 17" and 16" stock tires used by Dodge are within 0. 2% of each other. The 3. 73 axle ratio on the 3rd gens IS NOT the same as the 3. 54 on the 2nd gens.



I have an Excel worksheet on my website at http://www.klenger.net/dodge/general-reference/gear-speed-calculator.xls that will show RMPs and vehicle speeds for different size tires, transmissions, and axle ratios that may help.

 

[John - K5AWO]

..... We do about 6 tows (about 400 miles each) per year .....



Leaning towards the 3. 73 for a couple of reasons... .

Go with the 3. 73 ratio for mpg. Your anticipated towing needs don't even enter into the equation because of the very low frequency and short miles.



Even if you had to pull the 5er w/OD off 100% while pulling the 5er, that is not enough of a reason to not go with 3. 73 ratio.



Obviously you won't be needing to stay out of OD 100% of the time when towing. On the flat terrain your truck will pull OD quite happily.



Just for grins, let's say you have to pull 25% of those towing miles up a 3%-4% grade and you need to get out of OD. Assume that in OD you are towing at 65-70 mph. And assume you have to fall back to 55-60 out of OD to pull the grades.



6 trips x (400x2) = 4800 miles. 25% of that is 1200 miles/year with the OD off.



The time required to travel 1200 miles at 70 is 17 hours.

The time required to travel 1200 miles at 55 is 21 hours.



Are you willing to sacrifice higher MPG as a daily driver just to save yourself 4 hours a year while towing?



I'm not. I will go for the 3. 73 gears.



-John

 

[jelag]

I own an 04 that pulls a 20K lb trailer most of the time... . My 04 couldn't do the job up and down the 6% grades here in the Pacific Northwest without the 4:10. My son has a new 04. 5 with the 3. 73's and he pulls my 12K lb fifth wheel trailer with no problems around the northwest... . If I was in your shoes. . I'd order the 3. 73 with no regret... I've just ordered a new 05, and again went back to the 4. 10... .



Hope this helps...



Jim

 

[Sherman]

bombing

I own an 04 that pulls a 20K lb trailer most of the time... . My 04 couldn't do the job up and down the 6% grades here in the Pacific Northwest without the 4:10. My son has a new 04. 5 with the 3. 73's and he pulls my 12K lb fifth wheel trailer with no problems around the northwest... . If I was in your shoes. . I'd order the 3. 73 with no regret... I've just ordered a new 05, and again went back to the 4. 10... .



Hope this helps...



Jim

Jim,Iassume that since you work these trucks that you leave them stock?Am I assuming correct?