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 Post subject: Re: Towing capacity
PostPosted: September 19th, 2016, 1:34 pm 
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Joined: July 31st, 2014, 1:01 am
Posts: 1914
Location: 1999 Concourse
Presuming you have the V-10, I can give you figures for my '99, and from what I know (I used to have a 1997; friend has a 2003) they should be the same on your rig. BTW, you may have either a 1999 or 2000 Ford chassis on your 2000 Chinook.

Pardon me if you already know this, but...

So, first of all, there is a whopping, super-huge looking GCWR (gross combined weight rating) of 18,000#. Whee! So you'd think that since the Chinook weighs around 10,000#, you'd be able to tow 8,000#. But nope, not even close, for a number of reasons. Towing is like anchoring a boat: Only the weakest link counts, and that is what sets up your maximums.

Here are the categories, plus acronym definitions:

GCWR = Gross combined weight rating. This is the whole shooting match, all-up.

GVWR = Gross vehicle weight rating. This is how much the Chinook can weigh. It would include any tongue weight you have from a trailer, anything you have in the hitch (motorcycle rack), etc. Basically any weight that will transfer to the wheels of the Chinook.

GAWR-R = Gross axle weight rating, rear. This is how much weight you can have on your rear axle (Chinook).

GAWR-F = Gross axle weight rating, front. This is how much weight you can have on your front axle (Chinook).

Hitch rating. This is the rating of whatever hitch you have on the Chinook. If it's low, it can be the weak link. OTOH, if it's 20,000#, that doesn't raise any of your ratings.

Receiver/ball rating. This is the weight rating of the receiver/tow bar/hitch ball you put in to tow. As above, it can lower, but not raise ratings.

Some of these ratings (GVWR and Axle ratings) are on the door jamb sticker. Tow rating (which is somewhat meaningless, as shown below) is in some Ford manuals and Chinook literature. But you can never "make" either of these, so let's go on.

Now the job is to figure out which is the weakest link. Some can be raised; some are simply what limits your real life towing capacity.

--GCWR is 18,000#. That's definitely not going to be the "weakest link." Far from it.
--GVWR is 10,700# (on my rig, likely yours too). This is on the door jamb sticker from Ford. This may be a "stopper," but read on.
-- GAWR-F is 3,700#. I have plenty of capacity here (but weigh your own rig to be sure).
--GAWR-R is 7,500#. On my rig this is the "stopper" for towing capacity. In other words, it's the number I reach first, in the variety of numbers that contribute to tow capacity. GVWR is not far behind.
Hitch rating: I'm not sure I've seen a hitch rating on the Chinook's hitch. I would think it would be at least 5,000#. Since I can't tow much more than about 5,000# without going over other ratings, I'm fine with it.
Receiver/ball rating: This should be marked on any receiver/ball you buy. I think mine is 6,000# (I have a couple though, depending on what I'm towing).

When I'm towing my boat, the trailer weighs around 4,600# (weighed on scale - the only numbers you can really trust). About 330# of that is tongue weight. Because of physics, that 330# translates to around 550# added to the rear axle. Without boring you will all my actual scale figures, I can say that my normal rear axle weight (Chinook alone, loaded) is around 6,900#. Hence when I'm towing the boat, the rear axle weight is around 7,450# That's just about at the limit. So I consider my practical trailer towing weight to be around 5,000# (this is with a tandem axle trailer, where the tongue weight can be 5-7% of the trailer weight; single axle trailers recommend more like 10%).

If towing a car "four down," then there is no tongue weight. So in that case you could tow more -- if you were able to determine that the Chinook built in hitch was up for it (ASAP Metal Fabricators, in Yakima, Washington, likely made the hitch/step combo for Chinook. They are still in business so might be able to shed some light on it).
--

Although not specifically for the Chinook, the Ford "tow rating" for a van with the V-10 and 4.10 gears is 10,000# This is not anywhere on any Ford van that I know of; rather it is in manuals. As you can see by the figures above, there's really no way to do this without horribly violating the other figures. This also held true for my previous Ford van (camper van). The Ford tow rating could only have been used if I had sawed everything out of the van and taken it to the dump. In other words, MAYBE with a bare van I could have gotten up to the tow rating without "breaking" the other Ford ratings, but only maybe.

So, in summary, towing capacity depends on multiple factors and ratings, and you have to see which is the "weak link." Some weak links can be raised (for example, if your drawbar/ball are rated too low). Others really can't be (axle ratings, GVWR, etc.). Many Chinooks can probably tow 5,000#, but weigh things at a scale to be sure (trailer and boat makers are notoriously "optimistic" about their real weights), and keep a close eye on your rear axle rating especially.

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 Post subject: Re: Towing capacity
PostPosted: October 15th, 2016, 7:28 pm 
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Joined: March 22nd, 2015, 7:45 am
Posts: 446
Location: Northern Virginia
Since the talk is about towing, I happened to come across this short video on trailer weight distribution: https://www.youtube.com/watch?v=4jk9H5AB4lM

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 Post subject: Re: Towing capacity
PostPosted: October 16th, 2016, 7:06 am 
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Joined: July 31st, 2014, 1:01 am
Posts: 1914
Location: 1999 Concourse
Amazing how the right video can clearly show a concept in less than a minute, isn't it?

That's why at least 10% tongue weight is recommended on single-axle trailers. Tandems act a little less strongly that way, so they can have a bit less tongue weight (5-7%). And then something like a towed car (four wheels down) has no tongue weight at all (by design), so doesn't have this factor.

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