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Old 01-29-2009, 10:26 AM   #1
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Towing Capacity Formula

I'm considering buying a '99 25' Safari.For now, I'm planning to pull it with a '88 Ford F250(5.8L,3.55 Rear axle Ratio). I bought it new, have taken care of it and have had no trouble. It has 135,000 miles but looks great-no rust. Is there a formula or a set of formulae that will tell me what trailer weight the truck is capable of towing? Thanks, Lloyd
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Old 01-29-2009, 10:39 AM   #2
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No set formula Lloyd, but if you have the O/M it should have the tow ratings. I can't see a 250 not being capable, 5.4 w/3:55 might be a little marginal in the mountains but the truck should do pretty well, go for it!!

We did 5years with an underpowered TV, just think slow and safe. Plus we didn't know any better.
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Old 01-29-2009, 10:46 AM   #3
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Read all the threads on towing, start screaming "what did I just read?", hitch up the Ford and your Airstream and go camping.

The better answer is to read those threads. You will find much disagreement, but out of it all you should be able to understand it after a while. Everyone has to go through this and most of us come to an answer.

Does your Ford manual give you all the info on GVWR, GCWVR, and payload? The Safari should have all the pertinent weights for it on the inside of the wardrobe door. You will need a weight distributing hitch also. There's a lot of info on those too on the Forum and you will find people get pretty attached to their hitches, though not as much as they do to their trucks. Your rear axle ratio seems kind of low for towing. Does the Ford have a towing package? Does it have the right electrical connection for the Safari? Does it have a weight distributing hitch receiver?

Welcome to the Forum. You will be able to find out just about anything you need to know here.

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Old 01-29-2009, 11:26 AM   #4
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Lloyd;

Welcome to the forums. I am not going to repeat everything that Gene or Robert told you except, get you a good hitch. I had a 27' Airstream before I moved up to the unit I have now and I towed it with a 1/2 ton Suburban and didn't have much problem with it. With the 5.8 (350 cid) the only problem you might have is in mountainous country. If you have the automatic transmission with an overdrive, by all means take it out of overdrive when pulling the trailer. You wil burn up your transmission with it shifting back and forth if you don't. Good luck and happy camping.

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Old 01-29-2009, 12:18 PM   #5
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Let's do a story problem! Or not.

X = curb weight of your vehicle
Y = total weight of passengers and cargo
X + Y = Z or "how much your truck really weighs when you are rolling down the road

Z should be < gross vehicle weight rating of your vehicle

A = curb weight of your trailer
B = total weight of "stuff" in the trailer including water/wastewater

A + B = C or how much your trailer really weighs when you are rolling down the road

C should be < gross vehicle weight rating of your trailer.

Z + C = K or the total weight of your truck and trailer combined.

K should be < the gross combined weight rating of your truck.

And who said math ain't fun?
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Old 01-29-2009, 12:22 PM   #6
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Quote:
Originally Posted by ROBERT CROSS View Post

No set formula Lloyd, but if you have the O/M it should have the tow ratings. I can't see a 250 not being capable, 5.4 w/3:55 might be a little marginal in the mountains but the truck should do pretty well, go for it!!

We did 5years with an underpowered TV, just think slow and safe. Plus we didn't know any better.

And if you don't have the manual, you should be able to contact the manufacturer and if you provide them the VIN, they can easily access info on all specifics of the vehicle and give you the tow rating. I did that with my last GMC truck.

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Old 01-29-2009, 12:37 PM   #7
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I can't argue with what Hampstead writes, but if you don't know what "<" means, it makes no sense. It means "less than". Somehow I got through high school without learning that (since it was so long ago, maybe those symbols didn't exist then) and more lately have had to ask my wife what they mean. She's the one with the two B.S. degrees (my BS certification is more informal). In our next class, we will study ">".

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Old 01-29-2009, 02:41 PM   #8
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8500 #s is the tow capacity for a (1991 the oldest I can get to) F250 4X2 with a 5.8l. A 4X4 is down to 8200 #s. There is a F250HD I have a listing for and the tow rating is the same for 4X2 and 8000 #s for a 4X4.

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Old 01-29-2009, 02:43 PM   #9
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The manufactures specs are the best forumla. Because that was what the design was built for. Mant time cab style can make a difference for the same model, so engine, tranny and rear axle ratio are a good start, however there are other things too.

Great question.
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Old 01-29-2009, 06:00 PM   #10
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I had a 89 Bronco with a 359 engine. It wasn't the best engine that Ford ever made but it should be adequate to tow a 25 Safari with a 3/4 ton chasis.
I would worry about the transmission if it has never been rebuilt. The one in my Bronco lasted less than 100 k miles.
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Old 01-29-2009, 06:07 PM   #11
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The Bronco likely had 351 V-8. The Bronco wasn't the best tow vehicle because of high center of gravity and short wheel base. IN adition it came standard with 4X4 which added weight to the vehicle that limited the pay load. And it's tow rating was about 7200 #s.

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Old 01-29-2009, 06:10 PM   #12
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The Safari you are considering has a dry weight of 4900 #s and a total capacity of 6300 #s. Your pick up should be good with that.

http://www.airstream.com/files/libra...c5c1005fbf.pdf


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Old 01-29-2009, 10:08 PM   #13
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F-250 V-8 3.5 rear towing

My '76 F-250 Super Cab w/ OEM tow pkg 390 cid (6.4 liter) C6 auto 3.54 rear (140,000 miles) little 29" diamter 9.50x16.5 tires: easily towed a 2,000# trailer with a WWII WC-51 weapons carrier about 5,000# with stuff in both beds, total not more than 8,000#. No aerodynamics. Only about 1.5 mpg decrease in fuel milage, ~11 mpg to ~9.5 mpg using ssllloooowwwwwww take off with soft right foot. No hint of problem braking. At speed it rode beautifully.

Full pedal loading on long, long significant upgrades usually down from cruise controlle 65 mph to 45-50 mph. Altitude was less than 1,000 feet. 3.73 pulls better without the rpm fuel consumption of a 4.10.

Think 10% change for each gear ratio jump.

This torquey 390 truck will pull nearly anything but a full tank of gas. W/ its worn rings at 149,000, milage has rapidly dropped to ~8 mpg in heavy city traffic. In its oxide cosmetic defense, it has never collided with a car payment. It'll make any Airstream look gorgeous by comparison.

Remember you lose 4% power for every 1,000 ft. in altitude gain. After raw power, gearing is THE answer. Diesel torque is best, but the pure anti-diesel political ~$1/gallon penalty is an insult. Look into an over/under drive unit, I am - about $3,000. It doubles the gears.

I am planning to cool-hotrod the "antique" stronger 390, easily adding 50-70% more hp and torque, but will put 4.1 rear to go with 33" tires, so about the same effective ratio as OEM.

I also have a '72 3/4 ton Suburban 350 (5.7 liter) manual 4.10 rear on 29" tires which pulls in city traffic much better, but above 55 mph it gets loud at 3,000+ rpm. It always gave 11-12 mpg no matter what. With the 4.1 or 4.56, I am switching to 32" tires, o/d transmission, .72 overdrive unit, and going with at least a 383 cid (6.3 L) to 427 cid (7.0L) after mkt small block, with at least a 100% gain in power and torque.

I am hot rodding both V-8s to pull 10,000# at 10,000 feet, 31 and 34 footers. These old trucks were built in the pathetic low power exhaust emission political detuning nuttiness of the '70's. Your 5.4 L is only better, with room for improvement itself.

God bless no exhaust rules on old trucks, yet... No $1,000+ failed chip for me; that money buys robust engine and gearing power.

Think about serious tinkering with your almost antique. It is fun.

Always use best quality LT load range E tires. 70 ratio feels better than taller aspect. I have no experience with newer 65 or 60 ratios, but I like some air in my tires. Old rubber is 5 years. Be safe.

Road trip stories are always better if you survive to tell them yourself.

Remember an economy car is one that's paid for and a luxury car is one that gets you there and home again.
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Old 01-29-2009, 10:17 PM   #14
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Quote:
Originally Posted by LloydN View Post
I'm considering buying a '99 25' Safari.For now, I'm planning to pull it with a '88 Ford F250(5.8L,3.55 Rear axle Ratio). I bought it new, have taken care of it and have had no trouble. It has 135,000 miles but looks great-no rust. Is there a formula or a set of formulae that will tell me what trailer weight the truck is capable of towing? Thanks, Lloyd
Swap your 3.54 gears for a set of 4.10s and you'll be set. The difference between 3.54s and 4.10s (when dealing with tall tires like your 235/85-16s) is HUGE!

Check your timing chain for stretch. A stretched timing chain will retard your cam timing which will reduce low-end power, EXACTLY what you DO NOT want for towing a trailer.
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