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Author Topic: What can I tow with my truck? Modifications necessary?  (Read 3623 times)

7.3diesel

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What can I tow with my truck? Modifications necessary?
« on: September 01, 2014, 12:03:24 PM »
TRUCK: 1997 F-250 Heavy Duty 7.3L Powerstroke 4x4.

There seems to be lots of detailed information about weight (dry v. loaded, what the truck's rated at, etc). According to Ford, provided I'm reading the document right, the GCWR for a 1997 4x4 manual 7.3L F-250 is 20,000lbs & 14,000 trailer weight. What is the maximum weight I can safely tow?

So I'm just now starting to investigate fifth wheels & I have a few novice questions that I'm hoping the community can help me with:

What modifications, if any, will improve ride quality & safety of my 1997 F-250 Heavy Duty 7.3L Powerstroke 4x4 when hauling a 5th wheel?
I'm currently looking into the TorkLift StableLoad, sway bars, add-a-springs, helper-spring kits, airbags & tires. I'm starting to get a bit overwhelmed and afraid of being sold something at the RV dealership that I can't safely tow... Does anyone have any recommendations on any of these mods?

Roughly at what trailer weight do people need to upgrade duallies?

Any experienced recommendations, suggestions & stories are much appreciated.

Thanks in advance!

keymastr

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Re: What can I tow with my truck? Modifications necessary?
« Reply #1 on: September 01, 2014, 01:23:44 PM »
It all depends on how your particular truck was outfitted from the factory. The manuals and spec sheets you find online only give general weights but usually do not include all the options like power seats and the like which will affect the weight somewhat.

If you look on your drivers door sill there should be a yellow sticker with tire loading info on it and it will include your axle weight as delivered from the factory and the gross weight each of those is allowed to carry. By subtracting the delivered weight from the allowed weight you get your true cargo capacity for your truck.

Gary RV_Wizard

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Re: What can I tow with my truck? Modifications necessary?
« Reply #2 on: September 01, 2014, 08:59:15 PM »
You can tow at most the weight difference between the F250 and its GCWR, so the first task is to weigh it with you and your usual passengers in it, plus full fuel. Next, since you are looking for a 5W, you need to learn the payload capacity, i.e. how much weight the truck can carry in the bed. A 5W puts 20-25% of its actual loaded weight on the hitch, so the truck has to be able to carry that.

I had a 1999 F250 diesel and it was pretty well maxed out with a 10,000 lb 5W. It pulled it fine, but the rear axle was a bit overloaded.

You will also want an exhaust brake added to that Powerstroke diesel, to help you stop the rig when needed.
Gary
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VallAndMo

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Re: What can I tow with my truck? Modifications necessary?
« Reply #3 on: September 02, 2014, 01:50:32 AM »
Hi 7.3diesel,

Great advice from Keymastr and Gary. I would add that you should pay attention to individual (front/rear) axle capacities: when you go weight your truck (fully loaded, as Gary said -- don't forget additional stuff you'd like to carry in the cab or in the bed) do it in a place where you can get separate weighting for each axle. Then add 25% of the trailer weight to the rear axle and see whether it's below axle capacity. Don't forget to add the hitch weight if you don't have one installed already.

Cheers,
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   Vall.

7.3diesel

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Re: What can I tow with my truck? Modifications necessary?
« Reply #4 on: September 02, 2014, 11:55:39 AM »
Thanks, these are exactly the answers I was looking for.

I had a 1999 F250 diesel and it was pretty well maxed out with a 10,000 lb 5W. It pulled it fine, but the rear axle was a bit overloaded.
Can anything be done to strengthen the axle without going to a dually? Is there such thing as forged axles for example?
What's the difference, if any, between the F-250 & F-350 non-dually rear axle/suspension?
What's my rig's GAWR?

You will also want an exhaust brake added to that Powerstroke diesel, to help you stop the rig when needed.
I just ordered a full turbo-back exhaust for my Powerstroke. Where in this system does the exhaust brake mount? After the turbo? After the downpipe? Anywhere?
Thanks in advance.
« Last Edit: September 02, 2014, 02:48:29 PM by 7.3diesel »

SargeW

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Re: What can I tow with my truck? Modifications necessary?
« Reply #5 on: September 02, 2014, 03:19:38 PM »
Most aftermarket exhaust brakes are added right after the down pipe as it exits the motor.  The one thing to check first though is make sure that the valve springs are heavy enough to withstand the back pressure on the engine.  I'm not sure about the Fords, but for a while the Dodges were being produced with #30 valve springs. They had to be changed out to #60 valve springs in order to keep the valves from opening up and allowing the exhaust back into the cylinders.  Not sure if the same was needed with the Fords or not. 
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7.3diesel

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Re: What can I tow with my truck? Modifications necessary?
« Reply #6 on: September 02, 2014, 04:52:38 PM »
Most aftermarket exhaust brakes are added right after the down pipe as it exits the motor.  The one thing to check first though is make sure that the valve springs are heavy enough to withstand the back pressure on the engine.  I'm not sure about the Fords, but for a while the Dodges were being produced with #30 valve springs. They had to be changed out to #60 valve springs in order to keep the valves from opening up and allowing the exhaust back into the cylinders.  Not sure if the same was needed with the Fords or not.
Interesting. I did not consider the valve spring strength. Makes since! I'll ask about that in the Powerstroke forums.

Lou Schneider

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Re: What can I tow with my truck? Modifications necessary?
« Reply #7 on: September 02, 2014, 05:20:28 PM »
Quote
What's my rig's GAWR?

That should be on the tire pressure and weight card on the drivers side door jamb.

Ford Door Jamb card

The weight ratings are determined by the manufacturer, and while you may possibly be able to upgrade one or more components that contribute to the rating, there's nothing you can do to upgrade the rating itself.   If you exceed the rating you're still overloaded.
« Last Edit: September 02, 2014, 05:25:00 PM by Lou Schneider »

7.3diesel

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Re: What can I tow with my truck? Modifications necessary?
« Reply #8 on: September 03, 2014, 02:31:18 PM »
Front FAWR 4600 lb
Rear GAWR 6084 lb
GVWR 8800lb

7.3diesel

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Re: What can I tow with my truck? Modifications necessary?
« Reply #9 on: September 06, 2014, 02:47:15 PM »
I think I figured it out!
Data stickers & Understanding ratings

So, as I understand these explanations, the trailer's GVWR is not the same as the trailer's UVW.
The trailer's GVWR is the maximum weight the trailer's axles can handle: weight of the trailer + weight of (potentially) a lot of cargo is the maximum weight the trailer can safely have on its own axles.
The more important numbers to look at on the trailer, in order to know if the truck can tow it, is the Unloaded Vehicle Weight (UVW) & the Cargo Carrying Capacity (CCC). We need to add the the UVW + what we think our CCC's going to be to know if we can to it or not. GVWR means nothing for towing.
Example:
UVW of trailer: 7,000 lbs
CCC of trailer: 2,000 lbs
GVWR of trailer: 14,000 lbs
GVWR of truck: 10,000 lbs according to people I trust & 13,800 according to manufacturer
Since UVW + CCC = 9,000 lbs we are under 10,000 lbs. Conclusion: we can safely tow it!
In this case, if the CCC is 3,001 lbs + UVW = 10,001 probably unsafe for my truck to tow.
In this case, if the CCC is 7,001 lbs + UVW = 14,001 probably unsafe for the trailer to carry this much cargo.

This calculation does not take into account GAWR (Gross Axle Weight Rating) of truck. Which is just as important to calculate. The truck's Front Axle Weight Rating (FAWR) is 4,600 lb & it's Rear Axle Weight Rating (GAWR) is 6,084 lb.
The trailer will have 20-25% of its weight on the truck's axles (front & rear, but mostly rear).
In this case if our UVW + CCC = 9,000 lbs the Hitch Pin / Tongue Weight (the weight the truck's axles can hold with a fully loaded trailer pushing down on the 5th wheel hitch) is 1,800-2,250 lbs. The truck's axles can easily take it!
:)

elliott-maine

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Re: What can I tow with my truck? Modifications necessary?
« Reply #10 on: September 06, 2014, 03:52:37 PM »
I would still start by weighing the vehicle, each axle separately, with a full tank and everything you think you would be carrying in the truck and bed.  The weight of what you may be carrying can add up quickly.
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Gary RV_Wizard

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Re: What can I tow with my truck? Modifications necessary?
« Reply #11 on: September 06, 2014, 10:35:45 PM »
The GVWR of the truck tells you very little about what it can tow. It does relate to the Payload carrying capacity and thus relevant for a fifth wheel, but not much else. The GVWR is not the same as the trailer towing capacity - those are two different numbers.
Therefore this is just plain wrong thinking:
Example:
UVW of trailer: 7,000 lbs
CCC of trailer: 2,000 lbs
GVWR of trailer: 14,000 lbs
GVWR of truck: 10,000 lbs according to people I trust & 13,800 according to manufacturer
Since UVW + CCC = 9,000 lbs we are under 10,000 lbs. Conclusion: we can safely tow it!
In this case, if the CCC is 3,001 lbs + UVW = 10,001 probably unsafe for my truck to tow.
In this case, if the CCC is 7,001 lbs + UVW = 14,001 probably unsafe for the trailer to carry this much cargo.




Furthermore, you are still confused about trailer GVWR, UVW and CCC.  The UVW + CCC should equal the trailer GVWR. It makes no sense at all when you state
UVW of trailer: 7,000 lbs
CCC of trailer: 2,000 lbs
GVWR of trailer: 14,000 lbs
Gary
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Ernie n Tara

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Re: What can I tow with my truck? Modifications necessary?
« Reply #12 on: September 07, 2014, 10:06:05 AM »
Simply:

GCWR(truck) =< GVWR (truck) + GVWR(trailer)
   AND
GAWR (truck rear axle) =>(GVWR (trailer) 20 to 25%)) + Rear axle load (truck)

And you've met the requirements!

Ernie
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7.3diesel

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Re: What can I tow with my truck? Modifications necessary?
« Reply #13 on: September 08, 2014, 12:00:10 PM »
The GVWR of the truck tells you very little about what it can tow. It does relate to the Payload carrying capacity and thus relevant for a fifth wheel, but not much else. The GVWR is not the same as the trailer towing capacity - those are two different numbers.
Therefore this is just plain wrong thinking:
Example:
UVW of trailer: 7,000 lbs
CCC of trailer: 2,000 lbs
GVWR of trailer: 14,000 lbs
GVWR of truck: 10,000 lbs according to people I trust & 13,800 according to manufacturer
Since UVW + CCC = 9,000 lbs we are under 10,000 lbs. Conclusion: we can safely tow it!
In this case, if the CCC is 3,001 lbs + UVW = 10,001 probably unsafe for my truck to tow.
In this case, if the CCC is 7,001 lbs + UVW = 14,001 probably unsafe for the trailer to carry this much cargo.

Furthermore, you are still confused about trailer GVWR, UVW and CCC.  The UVW + CCC should equal the trailer GVWR. It makes no sense at all when you state
UVW of trailer: 7,000 lbs
CCC of trailer: 2,000 lbs
GVWR of trailer: 14,000 lbs

Probably because I just made those numbers up hypothetically. I wasn't ware that UVW + CCC = GVWR, but that certainly does make since.
*sigh* I'm still trying to find time in my schedule to weigh my truck.
Thanks everyone for helping.

Gary RV_Wizard

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Re: What can I tow with my truck? Modifications necessary?
« Reply #14 on: September 08, 2014, 12:29:23 PM »
All these terms are explained in the RV Glossary on this site.
Gary
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Tom

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Re: What can I tow with my truck? Modifications necessary?
« Reply #15 on: September 08, 2014, 04:51:55 PM »
The button for the Glossary is in the menu above.
Tom.  Need help? Click the Help button in the toolbar above.

7.3diesel

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Re: What can I tow with my truck? Modifications necessary?
« Reply #16 on: September 09, 2014, 04:25:51 PM »
Ok, so all this math has really got me curious about the differences between a 3/4 ton SRW, 1 ton SRW & duallies.

What are the real factory differences between a Ford 3/4 ton SRW & a 1 ton SRW? What specifically are the chassis differences between these two trucks?
In other words, what specific parts account for the higher GAWR?

Generally speaking, from my browsing today, it looks as though the towing capacity of a dually is actually not significantly greater than that of the SRWs mainly because of the added weight of the extra tires & such. From what I've been reading it seems like the dually is a moderately more stable towing vehicle (when larger vehicles pass going the other direction & on slick roads) with only a few hundred more pounds of towing capacity.

Whenever I do the math it seems like I won't be able to legally/safely pull any of the trailers I've seen that are over 30' with the truck I've got. Does my 3/4 ton SRW really only restrict me to 30' & under trailers?

Gary RV_Wizard

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Re: What can I tow with my truck? Modifications necessary?
« Reply #17 on: September 09, 2014, 07:30:47 PM »
Quote
Whenever I do the math it seems like I won't be able to legally/safely pull any of the trailers I've seen that are over 30' with the truck I've got. Does my 3/4 ton SRW really only restrict me to 30' & under trailers?

Quite probably so. Ford substantially beefed up the F250 SuperDuty in 1999, but your 1997, even with the diesel, is not so much of a horse. A case can be made that the towing specs on the 1997-1998 Heavy Duty  were very conservative, but nobody knows how much and Ford certainly isn't telling.  The biggest issue will be pin weight - the huge weight a 5W places right over the truck rear axle. You could probably pull around 13,000 lbs of 5W, but I doubt if the rear suspension, axle and tires could handle the additional 2600-3200 lbs of pin load. That means you are more likely limited to around 10,000-11,000 lbs max trailer weight. Whether that much weight is a 28-30 ft trailer or a 32-34 footer depends on the trailer construction, but the larger trailers tend to be sturdily built, so when you cross the 30 ft line the weight is usually on the high side too.
« Last Edit: September 09, 2014, 07:34:04 PM by Gary RV Roamer »
Gary
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7.3diesel

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Re: What can I tow with my truck? Modifications necessary?
« Reply #18 on: September 10, 2014, 09:34:21 AM »
Quite probably so. Ford substantially beefed up the F250 SuperDuty in 1999, but your 1997, even with the diesel, is not so much of a horse.
Fascinating; do you (or anyone) have any idea what was done to the SRW Fords to "beef them up"?

The biggest issue will be pin weight - the huge weight a 5W places right over the truck rear axle. You could probably pull around 13,000 lbs of 5W, but I doubt if the rear suspension, axle and tires could handle the additional 2600-3200 lbs of pin load. That means you are more likely limited to around 10,000-11,000 lbs max trailer weight.
10k-11k wet or dry?
"Beefed up suspension" shouldn't matter other than having the truck ride even if the weight's on the axles/tires anyway, right?
For me this begs the questions: What did Ford do to the axles? What tires should I be looking at getting?

Whether that much weight is a 28-30 ft trailer or a 32-34 footer depends on the trailer construction, but the larger trailers tend to be sturdily built, so when you cross the 30 ft line the weight is usually on the high side too.
This is the conclusion that the numbers & my math is leading me to.
According to my GAWR math, I should only be able to pull not much more than 14,000 lbs wet because it puts me at 2800 lbs hitch pin tongue weight (20%, which is best case because some say 25%) which I guess is why Ford set the "tow rating" for my truck at 13,800 lbs. Therefore, I don't think I should even be considering trailers over 11,000 lbs dry since I plan on full-timing, which seems to limit me to aluminum frame trailers under 32 ft. And as far as safety's concerned, especially in the mountains, responsibility to my family & other motorists on the road dictates that I probably should not even get a trailer over 8,000 lbs dry. I'm perfectly ok with settling for a smaller trailer if it means doing it safely.
But after all this research I'm curious what one really needs to tow one of these 36 footers with 4 slides & toy-haulers safely. At first I giggled at all the semi-truck rigs on the forums, now I understand - you're the ones who've actually done the math!

Does anyone know the real factory differences between a Ford 3/4 ton SRW & a 1 ton SRW (&/or 1999 Ford upgrades)?

Thanks for all the help everyone, I can't trust salespeople I don't know or Ford, so you -the experienced road warriors- are my only trustworthy source for figuring out how to do this safely.
« Last Edit: September 10, 2014, 10:01:14 AM by 7.3diesel »

Gary RV_Wizard

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Re: What can I tow with my truck? Modifications necessary?
« Reply #19 on: September 10, 2014, 11:14:21 AM »
Quote
10k-11k wet or dry?
Actual trailer weight, whatever it is. Pounds are pounds, whatever you call them.  The dry weight listed in the brochure is meaningless, since you never tow it completely dry.  At the very least you have some propane in the LP tanks and some residual water in lines, heater, etc.

Quote
do you (or anyone) have any idea what was done to the SRW Fords to "beef them up"?

Not the details, no. Probably on the list are things like stronger drive shaft universals, heftier axles, stronger transmission, bigger tires, etc. Typically the engineers look at the weakest link(s) in the chain and bump those up to reach whatever GCWR and Payload ratings they want to achieve, consistent with cost targets.  Then repeat the cycle for the next years spec challenge.  When Ford redesigned their heavy duty pick-ups in 1999 and introduced the Super Duty line, they reworked a number of things, then proceeded to further improve them over the years to get ever larger ratings.
Gary
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7.3diesel

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Re: What can I tow with my truck? Modifications necessary?
« Reply #20 on: September 10, 2014, 12:11:39 PM »
Yeah, year model does seem to play a big role in determining the differences.

After doing some forum searching I found several very interesting threads on this topic. This is the best one I've found thus far.

Given that beefier springs, shocks & blocks only serve to level your loaded vehicle & can easily be upgraded, what's more important -IMO- to look at for towing capacity are axle strength, tires & brakes.
2010 SRW F-350 gets: 1.50 Spline Minor Dia. (in.), 1.57 Spline Major Dia. (in.), 37 No. of Splines (Hub End)
2010 SRW F-250 gets: 1.36 Spline Minor Dia. (in.), 1.50 Spline Major Dia. (in.), 35 No. of Splines (Hub End)

Payload & towing capacity shouldn't significantly increase here. Ford might argue that there is a significant increase. Anyone got the numbers?

And according to this thread: "F-250 has vacuume brakes and the F-350 has hydroboost brakes."[sic]
« Last Edit: September 10, 2014, 12:18:23 PM by 7.3diesel »

jdq1986

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Re: What can I tow with my truck? Modifications necessary?
« Reply #21 on: December 28, 2014, 12:26:03 AM »
My truck is a 7.3 as well, but it's a 1993 pre-turbo.  If it helps you to know, I full time in a '03 Hitchhiker that is approaching 16,000 lbs. loaded and the truck has no problem whatsoever pulling it.  Not going to break any land speed records up a hill without a turbo, but it WILL get to the top.  Also, the rear shocks only compress about an inch and a half under the pin and that's including a full 150 gallon diesel tank, and two full 27 gallon (100#) propane cylinders in the bed that are with me any time I travel.

7.3diesel

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Re: What can I tow with my truck? Modifications necessary?
« Reply #22 on: December 29, 2014, 08:42:52 AM »
My truck is a 7.3 as well, but it's a 1993 pre-turbo.  If it helps you to know, I full time in a '03 Hitchhiker that is approaching 16,000 lbs. loaded and the truck has no problem whatsoever pulling it.  Not going to break any land speed records up a hill without a turbo, but it WILL get to the top.  Also, the rear shocks only compress about an inch and a half under the pin and that's including a full 150 gallon diesel tank, and two full 27 gallon (100#) propane cylinders in the bed that are with me any time I travel.
Wow, that's pretty impressive. Is it SRW or a dually? How's breaking performance?
Got any pics :)

jdq1986

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Re: What can I tow with my truck? Modifications necessary?
« Reply #23 on: December 29, 2014, 01:15:42 PM »
It's SRW. My profile pic is of my truck and trailer. Brake works good, never had any issue getting stopped in a hurry if need be.

jdq1986

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Re: What can I tow with my truck? Modifications necessary?
« Reply #24 on: December 31, 2014, 10:31:53 PM »
Just realized you can't enlarge the profile picture (or at least I couldn't figure out how).  Sorry for the poor lighting.


 

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