Towing Issues: Towing with a Jeep Liberty, black powder cannons, trailer tow group

Question
First, thanks for this incredibly helpful and generous service!

Our historical reenactment group has 2 black powder cannons, which are hauled on an 18-foot double-axle trailer. The whole shebang weighs right around 3000 pounds. We may miss an upcoming event due to the unavailability of our normal hauler, and we've been discussing whether my 2002 Jeep Liberty is up to the task. Our thoughts/conclusions are below, and I welcome any and all input you'd care to add:

** While the Liberty (factory Class III hitch) is rated by Chrysler at 5000, 3500 is a more practical limit, but we're still well under that so weight is not a big ussue.

** For the upcoming trip, I would only be hauling it about 3.5 hours away. Nonetheless, we all agreed that a transmission cooler should added.

** The trailer has electric brakes. I *think* the Liberty is equipped with the wiring needed, but am not sure. The sticker, under "Trailer Tow Group", says "Adaptor - 7 to 4 Pin, Wiring", and the trailer wiring socket appears to have the necessary pins, but we obviously need to be sure. Can you suggest a method to verify that?

Also under Trailer Tow Group it says:
"Engine Cooling - Heavy Duty". I assume that is good, but has nothing to do with transmission cooling.

Any other suggestions you have regarding this trailer and vehicle?

Thanks again!
-dave

Answer
If your vehicle is factory rated at 5000 pounds, then you can safely haul that much load.  You can assume the factory left a fairly generous safety margin in that calculation.

Here is a web site with excellent diagrams and explanations of trailer wiring (they are universal at the plug, but the wires going in are different colors, so this page also lists the wiring color schemes of different manufacturers.

U-haul stores have a good selection of adapter plugs, you don't need to rent anything to go in and buy accessories.

Your Liberty should have the electric brake wiring, but you WILL need the controller.  That you can also get at U-haul, or a good trailer sales business, check your yellow pages.

A transmission cooler is always a good idea, expecially if hauling where it gets really hot or where there are large hils/mountains.

You should have about 300 pounds on the hitch ball if the trailer weighs 3000 pounds.  I would recommend taking it to a truck stop or a grain elevator and getting it weighed loaded just to be sure what the weight is.

Here is how I roughly determine how much weight is on the hitch when I hook it up.

Say you weigh 200 pounds.  Measure a point on the hitch on your vehicle and then stand on the ball.  Measure again.  Say the hitch drops 2", then you are getting approx 1" drop per 100 pounds.  Now springs are not all that linear, but this is close enough.

So say you put your trailer on and the hitch drops 5"!  You know you are overloaded.  You want to move the load around till the hitch drops between 2 and 3".  2.5 would be real close.

THEN I recommend you have a load equalizing hitch and when you hook that part up, you want to load the bars so your hitch goes up to within about 1/2 to 1" of where it was unloaded.  The Load equalizing hitch will spread the load equally between the front and rear axles, so the vehicle will be lower a little, but not near as much as with just a bumper hitch.

Check with Reese and Draw-Tite to start your search for this type of hitch.  it isn't really 100% necessary if you are only going to be hauling one time, same with the tranny cooler if you aren't in the heat/mountains, or the distance is say only 50 miles.  

3000 pounds is not a huge load.  if it was closer to 5000 I would say the equalizing hitch was highly recommended, and the tranny cooler very highly recommended.  

The tranny cooler will be a benefit for the life of the vehicle, just don't get a huge one, and make sure it has a valve to that it doesn't open till the tranny has some heat in it, or you could have a cold transmission in the winter!

I hope this helps.

Don