Understanding your truck and knowing how much is safe to tow...

Disclaimer: this guide should not be taken as an "end all." Be prudent, use caution and know your truck's limits. NOTE: going over the GVW or GCWR as set by your vehicle manufacturer may be illegal, may cause your insurance to not pay on a claim in the event of an accident, etc. etc. etc. This is by no means a legal page, just an informational page about my findings. NOTE: all vehicles referred to in this page are Dodge Ram trucks with Cummins turbodiesel engines, either auto or manual, 4x4 or 4x2 unless otherwise noted.

First of all, please understand the difference between GVWR and GCWR. These are the Federal Motor Carrier Safety Regulation definitions:

FMCSA definition: Gross vehicle weight rating (GVWR) means the value specified by the manufacturer as the loaded weight of a single vehicle.

My interpretation: The maximum weight you can put in/on your truck when driving as a single vehicle (no trailer attached).

FMCSA definition: Gross combination weight rating (GCWR) means the value specified by the manufacturer as the loaded weight of a combination (articulated) vehicle. In the absence of a value specified by the manufacturer, GCWR will be determined by adding the GVWR of the power unit and the total weight of the towed unit and any load thereon.

My interpretation: The word on the street is that the most DOT officers will get your GCWR by adding the GVWR of your truck to your GVWR of trailer. You must never go over your GAWR (posted on the door jamb of the truck and the drivers side front portion of the trailer), however many people also report that they only check TIRE ratings, not axle ratings (GAWRs defined by the manufacturer are artificially limited by stock tires. E.g. my rear GAWR is 6084 which is the limit of two 235/85R16 or 245/75R16 3042 lb. tires). Inherently you are going to go over your truck's GVWR.

Does the DOT have a list of every vehicle ever created and know the manufacturer's specified GCWR? Even if they did, how would they know which engine, trans, or rear end gears I had (see below for further).

The method that the FMCSA and USDOT (should?) goes by the method of GVWR of power unit + GVWR of trailer (or total weight thereon) because it can be calculated on the spot. Does this mean I could hook up a 50 foot 5th wheel trail to my 1/2 ton pick up? No. There are plenty of other things to take into consideration, primarily: spring capacity, brake capacity, axle capacity, tire capacity.

Secondly, it is very clear that vehicle manufacturers have other interests in mind when they make up the vehicle's GVW and GCWR. With a 7 year, 70,000 powertrain warranty, they need to make sure they're not replacing everyones transmission who decides to hook up a large trailer to it.

Rumor is that for 2006, DC is lowering the warranty to 3 year, 36,000 miles, so with this, hopefully we will see a GVW increase.

Here is a link to the Dodge Towing Guide, that Dodge love's to bury deep on their website.

Here is how I know the Dodge declared "Gross combined weight ratings" are essentially bogus (and this is just this one example).

Take 2 vehicles: A 3500 dually with 3.73s, a 3500 single rear wheel with 4.10s, Dodge rates the dually to 21,000# GCWR and the single rear wheel to 23,000# GCWR. Someone please tell me how this has anything to do with safety, and I'll give you a dollar. This is more about Dodge replacing parts under--the 4.10 is going to give less resistance on the engine, transfer case, transmission, etc and therefore will cause less problems within their 70,000 powertrain warranty.

Now, it has been determined that the only mechanical differences between a 2500 truck and a 3500 dually is:

a) Aesthetics (i.e. badges, fenders, cab clearance lamps, etc.)

b) Bigger rear axle in some cases:
-3rd gen 2500 SO AUTO's got 10,000# 10.5" axle vs. 11,000# 11.5" axle
-In the 2nd generation, Dana70's were seen in automatics and 5spd's and Dana80's in 6spd "ETH" [high output] trucks.

NOTE: Apparently Dodge is now advertising trucks, even 3500's as coming with the 10.5" rear end. Not sure which rear end is actually showing up on the trucks. The fact is that in terms of load rating, either of these is more than enough.

c) Two additional rear wheels (skinnier tires to avoid rubbing but with similar load ratings per tire)

d) Overload springs on rear leaf packs. NOTE: 3rd gen [2003+] 3500 single rear wheel has overload springs. NOTE: 2nd gen 2500's had same suspension as 3500's.

e) Front brake rotor width are minutely larger on 3500 4x4's but not on 3500 4x2's (1.39" vs 1.26")

So in summation, In 2003, Dodge started offering a single rear wheel 3500. The difference between the inherently single rear wheel 2500 and the single rear wheel 3500 is overload springs on the rear leaf packs and cab clearance lamps. Prior to 2003, a 2500 is essentially a single rear wheel 3500.

More technical specifications of 2004 Dodge 2500 and 3500 trucks are located here.

Basically we are finding the limiting factor of what is stopping us from towing heavier. Given that the frame, brakes, suspension (except overload springs) are the same, that factor is the tires. My statements are based upon the knowledge that mechanically 2500's are the same truck as a 3500 minus the dual rear wheels, and minus the overload springs on 3rd gens.

Let's take a typical 2500 truck. The rear axle curb weight is about 2500# and the rear gross axle weight (which at its given rating is based solely on the tire limits), is 6000#. this leaves 6000# - 2500# = 3500# before hitting the rear gross axle weight rating (read: tire limit).

Go back to the fact that the only mechanical difference between the 2500 truck and the 3500 dually truck is the additional wheels which give additional load rating from the tires, and the helper springs which hold up the extra weight.

If the GVW on a dually is 12,000#, and the GVW on a 2500 is 9000# yet the only mechanical difference between the two is wheels/tires and overload springs, assuming you stay within the wheel/tire and spring limits, you should be able to load the 2500 truck above the stated GVW, as long as you are within the the wheel/tire and spring limits.

To take it a step further, if you have a 6000# rear gross axle weight rating, and 2500# of that is the rear "wet" weight of the truck, it leaves 3500# before you reach the rear gross axle (tire) weight rating.

On a typical gooseneck trailer, you ideally want 25% of the weight to be on the rear axle. 3500# x 4 = 14,000#. that is the maximum trailer weight i would want to pull assuming proper loading, a good brake controller, brakes on both trailer axles, etc.

NOTE: tire limit on the trucks with 265/70/17 tires is actually 3195# per tire, NOT 3000# per tire, adding even more of a safety margin. On 2002 and prior year trucks, 265/75/16's are rated to 3415# per tire, giving another 830# of safety margin! Another note is that 19.5" wheels/tires are available with HUGE limits. I ran Rickson 19.5's with 4940# per tire ratings.

Here is an example of my 2003 2500 truck with 265/70/17 tires rated at 3195# per tire:

description weight
wet (loaded) weight of truck (combined axles) 7500 lbs.
wet (loaded) weight of truck (front axle) 4500 lbs.
wet (loaded) weight of truck (rear axle) 3000 lbs.
tire capacity, rear axle 6390 lbs. @ 80psi
pin weight prior to reaching tire ratings (tire capacity - wet rear axle weight) 3390 lbs.
approximate trailer weight for allowed pin weight (pin weight * 4) 13560 lbs.
calculated max gcwr (gross combined weight rating) 21060 lbs.

Here's an example of my 2001 2500 truck with 265/75/16 tires rated at 3415# per tire.

description weight
wet (loaded) weight of truck (combined axles) 7000 lbs.
wet (loaded) weight of truck (front axle) 4000 lbs.
wet (loaded) weight of truck (rear axle) 3000 lbs.
tire capacity, rear axle 6830 lbs. @ 80psi
pin weight prior to reaching tire ratings (tire capacity - wet rear axle weight) 3830 lbs.
approximate trailer weight for allowed pin weight (pin weight * 4) 15320 lbs.
calculated max gcwr (gross combined weight rating) 22320 lbs.

NOTE: The calculated max GCWR is the max that you could theoretically run without going over the tire limits. You should NEVER gross combine tow above the GVW of your truck added to the GVW of your trailer. You also MUST make sure the trailer/truck is properly loaded. NOTE: The GVW of 2500 diesel trucks is 8800 for 2nd gens and 9000 for 3rd gens. 3500 single rear wheels have a 9900# GVW.

One thing I haven't gone into and know nothing about is how much the added width of the dually helps.

For 3rd gen 2500's that have no rear sway bar AND no overload springs, I would highly encourage getting both, or a sway bar and timbrens.

It is important to take many safety precautions when towing:

1) Weigh your truck loaded (tools, kids, fuel, etc.) at a certified scale (flying j. or cat scale), then weigh your trailer loaded also. determine your individual axle weights (drive, steer and trailer) and go from there. make sure you never exceed tire ratings or axle ratings.

2) Make sure to properly load the trailer. gooseneck trailers should usually have a 25% pin weight.

3) Inflate tires to proper pressure COLD (e.g. 3000# per tire or 3195# per tire is at 80 psi). if you call the folks at www.retread.org, they will give you a FREE professional tire gauge. this is a $20 high pressure gauge, not a $0.99 piece of junk.

4) Ensure both trailer brakes are working properly and brake controller is calibrated - I'm going to throw this out there, basically, in my opinion, pendulum brake controllers are garbage. Get a BrakeSmart or a Jordan. Both of these are proportional to your foot on the pedal. This is important!!!

5) Tire rating is NOT everything. Keep in mind wheel rating, as well as tire pressure. I.e. the more the better because more pressure means a stiffer sidewall.

6) This is just the a brief overview of required safety precautions.

If you are wondering where i got the axle ratings, I went to the AAM website and converted kg to lbs and nm to lb. ft.:
axle gross axle weight rating axle torque capacity
aam 10.5" (2500 so automatics) 10020 lbs. 6231 lb. ft.
aam 11.5" (ho's and so 5-spd's) 10912 lbs. 8333 lb. ft.
aam 9.25" (front differential) 5511 lbs. 4646 lb. ft.

Standard tire options for 3rd gen dodge trucks:
tire tire rating @ 80 psi
michelin ltx a/s 245/70/17 load range e 3000 lbs.
michelin ltx a/s 265/70/17 load range e 3195 lbs.

Some resources i used:

Dana axle ratings: http://xj.cdevco.net/auto/pdfs

CAT scale locator: http://www.catscale.com/locator.shtml

Flying J scale locator: http://www.flyingj.com/highway/amenities/amenities.cfm

Converting torque nm to lb. ft.: http://locost7.info/converter.php

Converting kg to lbs: go to google and type in ### kg = ? lbs and then hit Google Search.

AAM axles used in 2003+ dodge trucks: http://www.aam.com/technology/tech_prod_driveline.html

Determining the load range of a tire: http://www.tirerack.com/tires/tirebran.htm (or look at the sidewall)
1) click on your brand
2) click on your model
3) click on "specs"

Dodge towing guide: http://www-5.dodge.com/towing5/D/home.html

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