Towing/Truck Newbie Trying to Understand

[Triton318]

I've been reading on this, and other sites, about towing as I need to figure out what I can safely tow with my truck (2003 F150 4.6L V8; automatic transmission; 3.55 differential).

Here are the figures for the truck (all in pounds):

From label:

GVWR: 6,050
Rear GAWR: 3,500

From Ford 2003 RV & Trailer Towing Guide

GCWR: 11,500
Maximum Loaded Trailer Weight: 7,100

Here's a formula I've run across several times: Tow Vehicle GCWR - Tow Vehicle GVW = the Maximum GVWR for the trailer.

Now, I don't have the GVW for my vehicle, because I haven't weighed it. This is the actual weight of the vehicle, fully loaded. However, shouldn't I be able to substitute GVWR for GVW, since the GVW should be less than or equal to the GVWR?

If I do that: 11,500 - 6,050 = 5,450. So, if I don't exceed the truck's GVWR, I should be able to pull a trailer weighing up to 5,450 lbs (fully loaded)? Is this correct?

I know there are other considerations to take into account. When I enter my figures using this online towing calculator (http://changingears.com/rv-sec-calc-trailer-weight-tt.shtml), it says the maximum trailer weight is 3,333 lbs.

Also, I'm confused about this: Ford says the maximum loaded trailer weight is 7,100. But 11,500 - 6,050 = 5,450. Shouldn't the maximum loaded trailer weight be 5,450?

So for the lengthy post -- just trying to get my head wrapped around this.

Thanks.

Jay

[Ron_Gratz]

Triton318 wrote:
Here's a formula I've run across several times: Tow Vehicle GCWR - Tow Vehicle GVW = the Maximum GVWR for the trailer.

The TV doesn't care about the TT's GVWR. It's the TT GVW that matters. IOW, the TV doesn't care how much the TT can weigh -- the TV only cares about how much the TT will weigh when you get it loaded.

Now, I don't have the GVW for my vehicle, because I haven't weighed it. This is the actual weight of the vehicle, fully loaded. However, shouldn't I be able to substitute GVWR for GVW, since the GVW should be less than or equal to the GVWR?

If I do that: 11,500 - 6,050 = 5,450. So, if I don't exceed the truck's GVWR, I should be able to pull a trailer weighing up to 5,450 lbs (fully loaded)? Is this correct?

No, some of the TT's weight, approximately 10% when using a WDH, is carried by the TV and is included in the GVWR. In your case, the GCWR might allow for a TT weighing about 6000#. However, the maximum allowable trailer weight often is determined by how much load the TV can carry rather than how much it can pull.

Also, I'm confused about this: Ford says the maximum loaded trailer weight is 7,100. But 11,500 - 6,050 = 5,450. Shouldn't the maximum loaded trailer weight be 5,450?

A GCWR of 11,500 and a published "max trailer weight" of 7100# implies that the TV's published curb weight is 11500-7100 = 4400#. Curb weight is the weight of a vehicle with no optional equipment installed.

Your TV might weigh closer to 4800# without passengers and cargo. If so, you would have a remaining payload capacity of 6050-4800 = 1250 available to carry the weight of passengers and cargo plus the WDH weighing about 100#. If passengers and cargo weigh, say, 600#, the remaining payload capacity available for vertical load imposed by the TT would be 1250-600-100 = 550#.

A properly-adjusted WDH causes a load equal to about 75% of TW to be added to the TV. This means the maximum TW could be 550/0.75 = 730#. Assuming a TW% of 12.5% gives a maximum TT weight of 730/0.125 = 5800#.

The assumed unhitched TV GVW (including WDH) of 5500# plus the assumed max TT weight of 5800# gives a GCW of 11,300#. So, for this example, the TV's GVWR rules -- but not by much.

So, depending on actual weight of the loaded TV, the maximum allowable loaded TT weight might be determined by GCWR -- or, it might be determined by the TV's GVWR.
You also might be close to exceeding the TV's rear GAWR.

Since you already have the TV, you should load the TV approximately as it would be loaded for a camping trip. Then find a scales where you can measure both the front and rear axle weights for your loaded TV. This will give you a proper basis for determining how much trailer you can tow.

Ron

[Campfire_Time]

You're not too far off.

Ford, and every other manufacturer, has a higher towing capacity listed than is often "real". Case in point is newer 1/2 tons that list a 9k towing capacity. The limiting factors are tongue limit and rear axle capacity. But that's more of an issue for travel trailers than utility trailers and boats, which have far less tongue weight than a TT. So a new 1/2 ton can probably tow a 9k boat, but not a 9k TT.

I'm not convinced you have all the right numbers. Don't go by online towing guides. That's generalized information. They list Max trailer weight for a properly equipped truck. It's not one size fits all. Engine size, cab configuration, and towing packages change that configuration. Your owners manual should have a chart showing possible configurations and corresponding towing capacities and GCWR. Those are the numbers you need.

You also have to subtract anything you carry in the truck, including people. So your real world capacity will be something under the 6500# cited by APT.

[APT]

Triton318 wrote:
...Ford says the maximum loaded trailer weight is 7,100. But 11,500 - 6,050 = 5,450. Shouldn't the maximum loaded trailer weight be 5,450?

You are counting tongue weight twice. Tongue weight will be part of the weight on the truck's axles, or GVW. If you load the truck up with GVWR including TW, then 5450 by your calculation should be about 85-90% of the trailer weight max, or closer to 6500 pounds loaded. That's the theory. Now reality.

Towing a high walled RV is hard work. You have to pull two sheets of plywood through the air at 60-65mph plus have power to accelerate and climb hills. I towed my TT with a 2003 F-150 Supercrew 4WD 5.4L/3.73 which did fine for two seasons. I would not be as happy with the 4.6L/3.55 combo. I recommend sticking to near 4k dry. Replace all your truck's fluids. Make sure it has a good transmission cooler. You may want to consider finding a more capable truck before the RV.