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Old 02-21-2013, 09:36 AM   #43
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So basically SRW trucks can not tow very big or heavy 5th wheels w/o going over one or more of the limits.

But all you have to do is change the gearing to 4.10's. The tires will be ok?
If so, that is what I would do. Will they change the door sticker?

Anyway - I looked into changing the gearing about 3 years ago. At that time the dealer wanted $1,200.

If you change the gearing can you then tow the 5er that you like? If so, again that is a good way to keep your truck plus get a nice unit to live in.

I would advise getting the 5er over any bumper pull trailer because 5er's do tow much easier. The only TT that I would full time in is an AirStream trailer. It would be a crappy set-up with most of our stuff in the covered bed of the truck. There is no room or storage in the A/S trailer but they are cool.

In my 5er it is very comfortable I like the slides that really open it up. And it has a lot of inside storage.

Let us know what you do and good luck.
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Old 02-21-2013, 10:20 AM   #44
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So, with a laden curb weight (LCW) of 7,890 lbs, a GVWR of 10,100 lbs and a GCWR of 21,000 lbs, let's work the numbers.

GVWR - LCW = maximum pin weight of loaded trailer
10,100 - 7,890 = 2,210 lbs pin weight
2,210 / 20% = 11,050 lbs maximum total weight of loaded trailer based on GVWR

GCWR - LCW = maximum total weight of loaded trailer
21,000 - 7,890 = 13,110 lbs maximum total weight of loaded trailer based on GCWR

As was stated earlier, a SRW HD truck will generally run out of GVWR before it runs out of GCWR, and that's the case here. The manufacturer's GVWR is the limiter - changing axle ratios affects GCWR, but not GVWR, so if you want to stay within the manufacturer's GVWR, the 4.10 axle ratio won't help although such a change would improve real world towing performance.

See my signature. My truck was specifically ordered to get as much GVWR and GCWR as possible within the Ram/Cummins configuration (discounting the 4500 and 5500 cab and chassis trucks) at the time I ordered it. These trucks, unfortunately, aren't normally found sitting on dealer lots - I was unable to find one not only in the Houston area but anywhere in the state of Texas, so I've factory-ordered my last 2 trucks.

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Old 02-21-2013, 11:17 AM   #45
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But, now I run into the GCWR. GCWR of 21,000 - 10,100 = 10,900 trailer max.
No. You subtracted hitch weight twice. 10,900 is the max weight on the trailer axles, but not the max gross trailer weight. 21000 minus 7890 weight of the wet and loaded truck = 13110 max 5er gross weight.

10,900 trailer axle weight plus 2210 hitch weight = 13110.

Quote:
It is interesting that this vehicle, with JUST the gear ratio conversion, has such increased tow ratings (towing capacity from 13,400 to 16,400 and GCWR from 21,000 to 24,000). This tells me that, even though illegal and not worth the risk, this truck is mechanically capable (outside of axle ratio) of towing much more than the ratings.
The GCWR (and tow rating which is derived from the GCWR) tells you how much weight you can pull over most normal highways, including mountain passes on interstate highways, without overheating something in the drivetrain, and without being the slow-poke in the far-right lane holding up traffic.

Think of the rear axle ratio as a lever. The longer the lever the more weight you can move with the same power. A 4.10 axle ratio is 10% longer than a 3.73 axle ratio, so it can pull more weight at the same speed up a steep grade without overheating anything.

So yes, the GCWR is limited by the axle ratio. Move on up into bigger trucks with the same engine and tranny, but with longer levers of 4.30 or 4.56 or 4.88 and the GCWR is no longer limited by the axle ratio, but by something else, such as frame or axle weight limits. For example, 2004 chassis cab with 6.0L diesel engine and 5R110 automagic tranny:

4.10 ratio: F-350 DRW = 20,000 pounds
4.30 ratio: F-450 = 26,000 pounds (stronger frame)
4.88 ratio: F-550 = 33,000 pounds (stronger frame plus heavier-duty rear axle design).

If you looked at those three trucks with the model numbers covered over, you probably wouldn't see any difference except the different tires. The F-350 DRW and F-450 even had the same basic design rear axle, although the F-550 had a bigger stronger rear axle.
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Old 02-21-2013, 10:41 PM   #46
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Quote:
It is interesting that this vehicle, with JUST the gear ratio conversion, has such increased tow ratings (towing capacity from 13,400 to 16,400 and GCWR from 21,000 to 24,000). This tells me that, even though illegal and not worth the risk, this truck is mechanically capable (outside of axle ratio) of towing much more than the ratings.
GCWR or GVWR are not part of any legal weight issues regarding your or any trucks weight carrying ability. Only the trucks GAWRs are legal issues regarding how much load a truck can carry. In this case the trucks rear axle carries the load so its the number one concern from a legal issue.

I prefere to use the math on rear axle numbers. And as you did I came up with a 3400-3500 lb payload. The trucks front axle changes little if any so isn't a player in carrying pin weight duties. Dodge certifies the GAWRs so using them is safe.

IMO changing to 4.10 gears isn't needed for a 13k-14k trailer with the Cummins. I would pull the trailer first and then make a decision if the Cummins needs 4.10 gears. Folks, myself included, pulling 14-15k with the Cummins with the 3.73 have no issues doing so.




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Old 02-22-2013, 01:45 AM   #47
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To many numbers. The BH has 7k axles and needs G tires to ne hauled properly. I do have a torque/power gauge and the Heartland trailers do haul much easier then any previously owned trailers by 30%. A TT trailer is a bear to tow compared to a 5th wheel. Get what you want because you will never be satisfied and will waste in trades. Its easierto upgrade the truck. But with my experience you will be OK. My unit is loaded to the Max and on 4 years my F250 has been great. You only get more weight loaded on the powertrain by towing with a duelly.
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Old 02-22-2013, 04:52 AM   #48
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OK, there you have it from both camps. Either size your tow vehicle within the manufacturer's ratings, or ignore them. The choice is yours.

Rusty
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Old 02-22-2013, 07:43 PM   #49
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...GVWR is a manufactures rating.
...RAWR is a manufactures rating.
...FAWR is a manufactures rating.
...GCWR is a manufactures rating.
... Tire placard numbers are a manufactures rating.
... numbers from a brochure are manufacturers numbers.
...truck makers website spec sheet numbers.
Did I miss any....

If staying within all the numbers is your thing thats fine.
However no one is going to think badly of you for your decision.
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Old 02-22-2013, 08:13 PM   #50
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Quote:
Originally Posted by caissiel View Post
You only get more weight loaded on the powertrain by towing with a duelly.
.
And just how does that work? Whether you tow with a under rated SRW or a properly loaded dually, the truck will see the exact same weight from the trailer. The dually will have the capability to haul more weight in pin weight and stay within manufacturers rating.

What is your loaded GVWR and rear axle GAWR and actual weights loaded and unloaded.

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Old 02-23-2013, 08:09 AM   #51
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Towed 3 years all over eastern states with a Ford Ranger. Trailer weight 5600lbs, truck capacity 3500 lbs. Towed 9 years with a GM 2500. Trailer weight 11600 lbs. Truck capacity 8600 lbs with my 6.5l diesel but with 8.1 it was good for 12000 lbs. Actually it was a great truck served me well with a few after market improvement to the engine. The truck had great rear springs and drove great.
Then traded for the F250 and found it needed a boost in power to pull the same trailer and stay on cruise like the GM did and the springs were maxed out and drove like a buckboard. 10 MPG for me was OK sometimes 12 was achieved. Improved the rear springs and it was fine.
Traded for new Heartland trailer 4000 pounds heavier. With G tires as I had constant problems with the previous unit. The fuel mileage gain with new trailer is great as I never averaged less then 12mpg and up to 15mpg in southern states. The F250 is rated for 23000 combine weight and the trailer can stop 14000 lbs with its 7k axles leaving 9k for the truck. Also the load on the engine has dropped with the new trailer. After towing 6 years and programed as high as 125hp I have never driven the truck to any allarming numbers.

Notice I said driven. The driven because it all depends on the driver. As in NASCAR the driver is the key.
Why do transports with same diesel power can haul 80k lbs up the same hills.
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Old 02-23-2013, 08:18 AM   #52
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Well, that's certainly a unique method to look at sizing a tow vehicle, but self-justification is a marvelous tool when one is pulling a 39' 5th wheel with a 3/4 ton SRW truck.

I don't believe that's something we should be recommending to newbies to RVing, many of whom have never towed anything before.

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Old 02-23-2013, 03:31 PM   #53
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If staying within all the numbers is your thing thats fine.... However no one is going to think badly of you for your decision.
Probably wrong. A little thing in the current American society called liability. If you get into an accident where someone gets injured or killed while exceeding ANY of the manufacturer's weight ratings, then the lawyers, and probably the family, of the injured/dead party are going to think very badly of you. When they get done with you, you'll probably never again be able to afford a nice RV and tow vehicle.

GVWR is the manufacturer's weight rating most likely to first be exceeded when towing a heavy trailer. On my previous F-250 and my current F-150, GVWR was exceeded long before RGAWR or GCWR was even close.
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Old 02-23-2013, 06:44 PM   #54
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Well, that's certainly a unique method to look at sizing a tow vehicle, but self-justification is a marvelous tool when one is pulling a 39' 5th wheel with a 3/4 ton SRW truck.

I don't believe that's something we should be recommending to newbies to RVing, many of whom have never towed anything before.

Rusty
Well stated Rusty.....

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Old 02-23-2013, 08:29 PM   #55
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Probably wrong. A little thing in the current American society called liability. If you get into an accident where someone gets injured or killed while exceeding ANY of the manufacturer's weight ratings, then the lawyers, and probably the family, of the injured/dead party are going to think very badly of you. When they get done with you, you'll probably never again be able to afford a nice RV and tow vehicle.
Interesting theory.
However being over the mfg GVWR is not a liability issue, never has been, but no one will think badly of you for saying so.
Do you have a credible link that your liability theory has ever happened ?? No one else has either including our brothers and sisters that use these same trucks to make a living and are on the road 24/7 for the last 75 + years.
GVWR is not the determining factor in a overloaded vehicle.

Now if the truck was loaded above its registered GVW or loaded above its drive or steer axle rating then a lawsuit action can result if it caused a accident or a injury. Then said claims may happen. It can also result in vehicle(s) impoundment and the operators license suspended.

Now as far as your particular F250 or F150 goes over its GVWR before other ratings thats may be true in the older gen trucks. However not so for some (not all) of the newer gen trucks with those high GVWRs. As I stated above some folks are reporting going over the trucks RAWR/tire load capacities by using GVWR to figure payloads. The F150 with a 7700 GVWR and those small 4050 RAWR/P tires was one of them.
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Old 02-24-2013, 09:40 AM   #56
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Originally Posted by tuffr2 View Post
So basically SRW trucks can not tow very big or heavy 5th wheels w/o going over one or more of the limits.

But all you have to do is change the gearing to 4.10's. The tires will be ok?
If so, that is what I would do. Will they change the door sticker?

Anyway - I looked into changing the gearing about 3 years ago. At that time the dealer wanted $1,200.

If you change the gearing can you then tow the 5er that you like? If so, again that is a good way to keep your truck plus get a nice unit to live in.

I would advise getting the 5er over any bumper pull trailer because 5er's do tow much easier. The only TT that I would full time in is an AirStream trailer. It would be a crappy set-up with most of our stuff in the covered bed of the truck. There is no room or storage in the A/S trailer but they are cool.

In my 5er it is very comfortable I like the slides that really open it up. And it has a lot of inside storage.

Let us know what you do and good luck.
thanks Tuffr2. See my latest post
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