Open Discussion on GCWR (Gross Combined Weight Rating)

DW_Gray

Well-known member
Weigh in on this discussion if you so desire.

Hypothesis:


GCWR in modern 250/2500 series trucks has nothing to do with the diesel engine and transmission combination capabilities.

Background:

In recent months there have been considerable discussions on various forums stating that exceeding GCWR in 250/2500 series trucks is an absolute no, no. Among the various reasons for not exceeding the GCWR have been that the engine and or the transmission would not handle towing trailers up to 50% over published towing capacity of some the 250/2500s when using the Automated Safety Hitch System (ASHS).

Known facts or near facts based on interpretive information:


  1. As of February 2010, the capacity of the Chevy/GM Allison 1000 transmission is capable of handling 33K pounds GCVW. (It may be more now.) http://goo.gl/Ow26Ss
  2. The 2014 Chevy/GM Duramax engine with the Allison 1000 transmission tops out at 30.5K pounds GCVW. http://goo.gl/miuHVX
  3. The 2014 RAM Cummins engine with the 68RFE transmission tops out at 30K pounds GCVW. Since RAM introduced the AISIN transmission for higher capacity, let’s assume that the 68RFE limit may not be much over 30K GCVW. (The new AISIN transmission tops out at 37,500 GCVW with the same engine but most likely that’s not the total limit.) http://goo.gl/uAVevO
  4. The 2014 Ford Power Stroke with the 6R140 TorqShift 6-speed SelectShift[SUP]®[/SUP] transmission tops out at 35K GCVW. http://goo.gl/OSW8Ap
  5. Identical diesel engine and transmission combinations are used in all respective 250/2500 and (350/450)/3500 series trucks.
  6. The respective brand frames for 250/350/450/2500 and 3500 are identical.
  7. The respective drive shafts for the 250/350/450/2500 and 3500 are identical.
  8. STRIKE: The respective differentials and axles for the 250/350/450/2500 and 3500 are identical. (After additional review on a different parts website, there could very well be differences between SRW and DRW axle assemblies.) Recalling from memory of past reading, I don't think that would make any difference in the overall capability between the two. From what I've read, these assemblies are rated much higher than what the auto makers limit them too.) Any additional input on this is welcome.


Discussion:

Now, if all these respective vehicles have the same common powertrain combination as referred to above, the question to be answered is: What prevents the 250/2500 from having the same towing capacities as the respective bigger brothers?

By reason of deduction, what’s left in the powertrain is the gear ratio, brake assemblies, wheels, tires and an important load bearing component, the springs.

Therefore, is it not reasonable to conclude that one of or a combination of the remaining components are responsible for lower tow ratings for the 250/2500 vehicles?

Is it not also reasonable to accept that if these remaining components were replaced or modified, the 250/2500 would be equally capable of towing the same weight as its respective big brothers?

If the answers are yes to the above questions, please explain the reason that using the ASHS is not a reasonable option for owners of 250/2500 vehicles to tow heavy trailers equal to the ratings on respective big brother vehicles.

******************************************

I’ll start with the first response.

Without aftermarket modification, the late model stock Ford F250 is not a candidate for using the ASHS. This is due to the gear ratio limitation. The F250 Power Stroke comes only with a 3.55:1 gear ratio. I recommend nothing less than 3.73:1.

And one final note, I have edited my article on the Automated Safety Hitch System reflecting my recent research. Click here.
 
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danemayer

Well-known member
  1. The respective drive shafts for the 250/350/450/2500 and 3500 are identical.
  2. The respective differentials and axles for the 250/350/450/2500 and 3500 are identical.
Dave,

Are you assuming the components are the same or have you checked this out? I recall a thread a few years ago asserting that the rear axle part numbers differed on 2500/3500 Chevy if I remember correctly.
 

DW_Gray

Well-known member
Dave,

Are you assuming the components are the same or have you checked this out? I recall a thread a few years ago asserting that the rear axle part numbers differed on 2500/3500 Chevy if I remember correctly.

Not assuming. Spent countless hours looking at part numbers for late model trucks. Many of the early trucks do have different part numbers. I looked at the 2008, 2011 and 2013 trucks.
 
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mattpopp

Trouble Maker
Dodge does not put the upgraded Aisin or 850ftlb engine in the 2500. Only the 3500 gets it. But your argument would be true on Dodge 2003 to 2013 models.


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DW_Gray

Well-known member
Dodge does not put the upgraded Aisin or 850ftlb engine in the 2500. Only the 3500 gets it. But your argument would be true on Dodge 2003 to 2013 models.


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You're correct Matt. The 2014 Ram 3500 with the AISIN is not a "respective" vehicle to the 2500. All the other 3500s with the 68RFE transmission would be though.
 

scottyb

Well-known member
Without aftermarket modification, the late model stock Ford F250 is not a candidate for using the ASHS. This is due to the gear ratio limitation. The F250 Power Stroke comes only with a 3.55:1 gear ratio. I recommend nothing less than 3.73:1.

This would apply to the F350 SRW also. The 3.73 is only available on the F350 DRW.
 

MTPockets

Well-known member
My career was working with plant maint/engineers troubleshooting equip, selecting various items including gearboxes (speed reducers). These were rated based on design load/speed requirements (among other things); part of the selection process involved the gearbox Class rating, Class I, Class II, and Class III. Class III for the most severe duty. We in the parts business knew that many times the only difference between the three Class ratings was the price, and the label. True, if the customer needed Class III, the price was higher but all components were identical. Reality was they were paying for the guarantee and warranty for the Class requested. This didn't apply to all sizes, but it did apply often.
 

dave10a

Well-known member
what about the brakes and stopping power? BTY gears ratio is a torque multiplier. The differential is sets the over-all torque multiplier when the transmission is in its highest gear. Than means if you need more torque the transmission allows more by down shifting until you get to the lowest gear. I suspect the design engineers select gear ratio based on torque curves of the engine to provide the best torque/gear ratio and shift points for a particular load. The differential is the final drive ratio at the highest transmission gear and is most likely set for travel speed to provide the less transmission gear hunting for the anticipated load. So if the transmission is hunting down shift to a point to stop hunting. One can also get a manual transmission and do the torque multiplier routine the old fashion way :)
 

DW_Gray

Well-known member
what about the brakes and stopping power? BTY gears ratio is a torque multiplier. The differential is sets the over-all torque multiplier when the transmission is in its highest gear. Than means if you need more torque the transmission allows more by down shifting until you get to the lowest gear. I suspect the design engineers select gear ratio based on torque curves of the engine to provide the best torque/gear ratio and shift points for a particular load. The differential is the final drive ratio at the highest transmission gear and is most likely set for travel speed to provide the less transmission gear hunting for the anticipated load. So if the transmission is hunting down shift to a point to stop hunting. One can also get a manual transmission and do the torque multiplier routine the old fashion way :)

I did not do a complete brake comparison but on two vehicles. Those two were identical. I reached a point of stopping the detailed comparison and left that open for the possibility that some 2500/3500 vehicles had different brake systems. Regardless, the ASHS has its own brake system and the capacity is nearly equal to all four brakes combined on tow vehicles.

The engine and transmission capabilities do not change regardless of the gear ratio. Manufacturers do not modify the engine or transmission when using different gear ratios.
 

mattpopp

Trouble Maker
what about the brakes and stopping power? BTY gears ratio is a torque multiplier. The differential is sets the over-all torque multiplier when the transmission is in its highest gear. Than means if you need more torque the transmission allows more by down shifting until you get to the lowest gear. I suspect the design engineers select gear ratio based on torque curves of the engine to provide the best torque/gear ratio and shift points for a particular load. The differential is the final drive ratio at the highest transmission gear and is most likely set for travel speed to provide the less transmission gear hunting for the anticipated load. So if the transmission is hunting down shift to a point to stop hunting. One can also get a manual transmission and do the torque multiplier routine the old fashion way :)

I can tell you that on Dodge from 2003 to 2013 pretty much everything was the same between the 2500 and 3500. Same axles (DRW was narrower), same brakes, could get 3.73, 4.10, and some of the later years you could also get 3.42. Only difference was leaf springs and front coils.

With added air bags to a 2500 your only limitation is tire rating. But you could remedy that with 19.5's as I believe you can get them rated up to 6,000lbs. In theory you could have the same rating as a 3500. One thing is the AAM 11.5" rear axle has around 12,000 lb rating from AAM. Dodge rates it much lower.


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scottyb

Well-known member
And the F-350 C&C is also available with 3.73's Brakes on 250's 2500's and 350's 3500"s are the same.

Where are you finding this? On their towing guide, it is only listed on the DRW. If you try to build it, it will add $1550 and convert it to a DRW. If you de-select DRW, it will go back to 3.31 or 3.55.
 

jnbhobe

Well-known member
you can only get it when you order a cab and chassis no box on the 14 it may have to be a Fleet order

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DW_Gray

Well-known member
Same axles (DRW was narrower)


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Are you sure about that? The ones I checked out were the same axle. The difference was how the wheel was made.

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Edit: 8: STRIKE: The respective differentials and axles for the 250/350/450/2500 and 3500 are identical. (After additional review on a different parts website, there could very well be differences between SRW and DRW axle assemblies.) Recalling from memory of past reading, I don't think that would make any difference in the overall capability between the two. From what I've read, these assemblies are rated much higher than what the auto makers limit them too.) Any additional input on this is welcome.
 
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MCTalley

Well-known member
At least for 2013, Ford rates the F-250 and SRW F-350 diesels at the same 23,500 GCWR. The DRW steps it up to 30,500.
 

DW_Gray

Well-known member
At least for 2013, Ford rates the F-250 and SRW F-350 diesels at the same 23,500 GCWR. The DRW steps it up to 30,500.

Yep. Years 2011-2014 are 23,500 pounds. Years 2002-2010 ranged from 20,000 to 23,000.

I suppose an ASHS could be beneficial for trailers in the 16K range since they would most likely overload the F250 rear axle.

I just question how well the 3.55 rear end will handle long mountain climbs. (Feedback welcome.)
 
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jnbhobe

Well-known member
Yep. Years 2011-2014 are 23,500 pounds. Years 2002-2010 ranged from 20,000 to 23,000.

I suppose an ASHS could be beneficial for the trailers in the 16K range since they would most likely overload the F250 rear axle.

I just question how well the 3.55 rear end will handle long mountain climbs. (Feed back welcome.)

I think tires are the weak link on an F-250 so that could be changed pretty easy. I tow 16K all over the central and east coast with a F-350 SRW and 3.55 gears with no problem.
 

porthole

Retired
SO - is this an open discussion for GCWR's or a sales pitch for a device that allows you to go over your vehicles ratings - "ashs"
 

HornedToad

Well-known member
Seems like a lot of the discussions on the forum are about
how/why you can haul a bigger trailer with a smaller truck,
and I got buy just fine haulin' with a 3/4 ton truck.

But think about it this way,
when you get ready for a trip,
Do you...
bring more money than you should spend?
buy more food than you can eat?
fill the cooler with more than you can drink?
pack more clothes than you can wear?
& tote more tools than required?

So why wouldn't you want more truck?
 

TravelTiger

Founding Texas-West Chapter Leaders-Retired
Seems like a lot of the discussions on the forum are about
how/why you can haul a bigger trailer with a smaller truck,
and I got buy just fine haulin' with a 3/4 ton truck.

But think about it this way,
when you get ready for a trip,
Do you...
bring more money than you should spend?
buy more food than you can eat?
fill the cooler with more than you can drink?
pack more clothes than you can wear?
& tote more tools than required?

So why wouldn't you want more truck?

Well said.


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