3.73 vs. 4.10 for towing

[Dean Upson]

The switch to the 17" tires was one reason for the 3. 73's. My 4. 10s fewer rpm on my '03 than on my 98. 5 with the same gears. I do not mind the higher rpm because I seldom drive over 65 and if I am towing it is more like 62 .

The worst truck I ever had for towing was a 94 3500 4x4 dually auto with 3. 54's. It was a great truck empty. If you tow heavy, I do not see where you can go wrong with the lower gearing.



Dean

 

[2003Cummins4Me]

Is it true that you cant get a new dually with the 3. 73's? I went online to build my truck and it wont let me switch to them. Ive driven two trucks back to back with the two different gears and I most definetly like the 3. 73's better... I would only recommed the 4. 10's if you are towing really heavy.

 

[DLeno]

Originally posted by Dean Upson

The switch to the 17" tires was one reason for the 3. 73's.

Dean, the 17" tires on the 3rd gen trucks have the same running diameter as the 16" tires on the 2nd gens. The reason for the 3. 73s had to have been performance -- and to take advantage of the higher max rpm of the new HPCR engine.



Doug

 

[JRMora]

quote:

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Originally posted by 2003cummins4me:

you cant get a new dually with the 3. 73's?

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I have an '04 dually with 3. 73's. I believe it still holds true for the 04. 5's, too.



I thought one of the reasons Dodge went to the 3. 73's was because of the change to American Axle. I didn't think AA had a 3. 54 carrier that would work in these axles.

 

[Casey Balvert]

I agree with Dean, the 17 inch tires on the 3rd gen dually has a tire diameter almost 1. 5 inches greater than the 97 dually. Both of my trucks have or had the 4. 10 axle and engine rpm for a given road speed is considerably lower. I like the 4. 10s but it really was the only reasonable choice since I tow 16,000 pounds.



Casey

 

[JRMora]

I went to Tirerack.com and looked at the Goodyear GSA and Goodyear RT/S specs and they say the 235/80/17 GSA's are 31. 8" diameter and the 235/85/16 RT/S's are 31. 5" diameter.



I believe the 235/85/16's were standard with the 2nd gen duallies. The 235/80/17's are statndard for 3rd gens.



FWIW



Juan

 

[Dean Upson]

Originally posted by DLeno

Dean, the 17" tires on the 3rd gen trucks have the same running diameter as the 16" tires on the 2nd gens. The reason for the 3. 73s had to have been performance -- and to take advantage of the higher max rpm of the new HPCR engine.



Doug

The larger tire diameter on my '03 gives me fewer rpm than I had on my stock 98. 5 dually with the 16' rims.



edit:

The tires on my 98 were: 215/85/16 = 30. 4" dia

03 are: 235/80/17 = 31. 8" dia

about 1. 4" diameter difference. I would have to do the math, I would guess that there is at least 200 rpm difference between the rpm on the two trucks and I run at 2000-2200 rpm at highway speeds.



Dean



Dean

 

[DLeno]

oh duh. forgot that the rolling diameter actually did change on the duallys. for the SRW, there is no difference when they went to 17"

 

[Dean Upson]

Originally posted by DLeno

oh duh. forgot that the rolling diameter actually did change on the duallys. for the SRW, there is no difference when they went to 17"

Doug,



You had me going on that one a little . I even had to make a phone call to Canada this morning to consult the famous Canadian sage and my good friend, Casey Balvert about this. I was pretty sure I knew what I had in both trucks.

The bottom line is that the rpm in the G3's, at least in the duallies is not as high as in the G2's.



Dean

 

[willy1947]

Thanks for all the input



I'm still very happy with my 3. 73's. I might reconsider the 4. 10's if I was hauling more weight, but for now these are working great.



All of this information has been very helpful. I've already recommended this site to a couple of friends.



Thanks again!

Dave

 

[DLeno]

hey Dean, just though about this again. -- the tire size difference doesn't explain 200 rpm, but it does explain 100 rpm. A diameter change from 30. 4" to 31. 8" is roughly 5% and the rpm change will of course be the same. so that accounts for 100 rpm at 2,000.



The change from 3. 54 to 3. 73 is only a small nudge more than that, so yes we can say that the new gears compensate for the taller tire.



And yes, what that means is that compared to your 98 with 4. 10s, to a 3rd gen with 4. 10s will run about 5% fewer rpms.



oh, on edit I almost forgot: heres a handy way to check the accuracy of your spedo when you don't have a gps or a radar gun Use one of those highway spedometer check stations --- the ones that start out at zero and go to 5 miles. Anyway count the number of "tenths of a mile" you are off, at the conclusion of the 5 mile check. take the "number of tenths off during 5 miles" and double that number. thats the percentage your spedo is off.



for example, if your odo reads 4. 8 miles and you actually traveled 5 miles, then you are "2 tenths of a mile off", and your spedo reads 4% slower than you are actually traveling. 4% of 60 is 2. 4, so when your spedo says 60, you are really doing 62. 4.

 

[Dean Upson]

Sounds good to me Here is a handy little caluclator for tire sizes. http://www.rx7turboturbo.com/robrobinette/tire_diameter.htm You will no doubt that the actual difference betwee the two tire sizes that I previously mentioned is 1. 141388" which would the rpm a wee bit closer to the 200 that I thought was the difference. This truck is so quiet it must seem like 200 rpm+



Dean

 

[Foxtrotter]

Another good place to check is the RPM calculator at the West Coast Differentials website



Paul

 

[RAMINSPEED]

If your'e going to put big tires on it go with th 4. 10's. I just got done pulling a 8,000 trailer and the lower gears would have been much nicer.

 

[ab7fh]

I had 3. 73s in my '01 and I have 4. 11s in my '03. I wish I had kept the 3. 73s. Mileage is poor and I turn too many RPMs to run efficently at high speeds.



I have thought about swapping gears or getting an OD unitl. Those OD units are big $$$$ though.