Trailer Life "Guide to Towing"

I think it just looked at towing and not payload capacity. Wasn't very useful to me.

I wouldn't put to much faith about tow ratings from a non Dodge/Ram publication. Dodge/Ram Body Builders guide website will have more up to date specs.

The numbers the op posted are for a 3.42 gears in all three trucks. The 3.73 gear change is available in the DRW which makes a 18130 lb tow rating.

Again, towing ratings, unless your towing a flat bed or a bumper pull TT are not much use. Especially when it comes to fifth wheel towing. Then its all about availablr payload.

I got my Jan Trailer life mag yesterday in the mail. I never even looked at the tow ratings guide before I threw it in the garbage can. I have better luck looking on each trucks web site under towing capacity.

Whiskey River wrote:
Got my Guide to Towing yesterday. I have a Ram 2500 long bed diesel 4x4, manuel 6spd so I checked these 3 Ram trucks and am somewhat confused by what I read. Larger truck, less towing?
Ram 2500 RegCab long bed,4x4 diesel,manuel6spd & 3.42:1 16,450#
Ram 3500SRW RegCab long bed,4x4 diesel,manuel6spd & 3.42:1 16,520#
Ram 3500DRW RegCab long bed,4x4 diesel,manuel6spd & 3.42:1 16,130#

So each truck set up with the same spec's given in the "guide" the Ram 3500SRW can tow 70 pounds more than the Ram 2500. And the Ram 3500DRW tows 320# less than the Ram 2500. What am I missing here?

A lot of it is about the 3.42 axle and keeping it cool. All three trucks have the same GCVWR of 24,300#. The SRW 2500 base is 60# heavier than the base SRW 3500. The DRW 3500 is 385# heavier than the SRW 3500 and 320# heavier than the 2500. Its all about the keeping the GCVWR at a number that the differential oil will stay at a spec temp in their maximum tests. When you take the max trailer weight and add it to the empty truck weigh they allow you between 468#-480# of cargo or tongue weight in the truck to keep the GCVWR at their number. So basically they say you can pull a 4 wheeled wagon of that weight with a couple people in the truck. LOL

Because Tow Ratings under SAE J2807 are determined by calculating GCWR then subtracting trucks BASE Weight (plus 150#/Driver, 150#/Passenger, 100#/optional equip and weight of tow package equipment) to arrive at MAX TOW Ratings.

Not sure about the 2500 number but the difference in the 3500's makes some sense. The truck's GCWR is probably limited by the manual transmission, so the heavier DRW will have a lower tow rating. Tow rating = GCWR - truck weight.

wilber1 wrote:
Not sure about the 2500 number but the difference in the 3500's makes some sense. The truck's GCWR is probably limited by the manual transmission, so the heavier DRW will have a lower tow rating. Tow rating = GCWR - truck weight.

Actually it does make some of the difference. The biggest effect is the final gear ratio. Heat buildup is a big part. The other factor with the higher gear ratio is the ability take off in reverse on a grade and the reverse gear ratio makes a difference also the ability to hold in park on a grade.

It's simple math. That combo of engine, transmission and rear axle is identical in all three trucks. They all have the same GCWR. The 3500 series trucks are slightly heavier empty, therefore they can tow slightly less weight. The higher payload ratings make the 3500 a better choice, although apart from rear suspension there is very little difference in the actual trucks, as evidenced by the minimal difference in empty weight.

transamz9 wrote:

wilber1 wrote:
Not sure about the 2500 number but the difference in the 3500's makes some sense. The truck's GCWR is probably limited by the manual transmission, so the heavier DRW will have a lower tow rating. Tow rating = GCWR - truck weight.

Actually it does make some of the difference. The biggest effect is the final gear ratio. Heat buildup is a big part. The other factor with the higher gear ratio is the ability take off in reverse on a grade and the reverse gear ratio makes a difference also the ability to hold in park on a grade.

In the example, they all have the same final drive ratio. Yes, changing the ratio makes a difference, partly for the reasons you explained but also because a higher ratio allows more torque to be applied to the wheels without increasing stress on the clutch and transmission.