Hi Jeepplr ... Did you have the trailer loaded?  If it was empty, (most likely) 1300 odd pounds to the rear axle isn't much stuff to load into the trailer... Forget about hauling four 1000# horses at the same time.

MHO based on:

Full load of 3 horses and stuff for three people in my 4 foot short wall 3H steel/alum trailer (no LQ) totaled 17,800 pounds.

It was empty.  I have my trucks owners manual and the 2500HD 8.1 or 6.6 diesel can have a max GCWR of 22,000lbs, so I am engine or transmission limited both are upgreaded but that is still a lot of weight to pull.

You are UNDER TRUCKED...

Jeeplr : I agree with Paul.  While you have upgraded your engine and transmission to some specification (You haven't said), your rear axle rating is the next weak link.  (not just the axle, includes the tires,springs, etc) You only have 1300 pounds of capacity left.  Unless you want to haul an empty trailer around, two horses alone will overwhelm the weight carrying rating of the truck. 

Under trucked yes, the trailer was too good of a deal to pass up. 

The engine has a supercharger for about 450hp and the tranny has a computer upgrade and I take it very easy on the truck,  sometimes.  The carrying capacity of the rear end I am not worried too much.  My longest pulls, Ohio to Colorado, will be with a 3700lbs Jeep sitting in the trailer backward with the trailer carring most of the weight.  I don't know the axle weights of that set up but once my Honey Do list gets shorter I will get that done.

Here is the other shoe that is about to drop...is your rear axle a semi-float or a full float??

http://www.off-roadweb.com/tech/0112or_semi_floating_and_full_floating_axles/index.html

Also, have you checked with Exiss about hauling a VEHICLE in a horse trailer?

Some trailer manufacturers will void their warranty for such an exercise...

The axle is a full floater and the trailer is a Lakota.  I think by loading the Jeep tail front and the engine hanging far aft I will not load my truck too much and not cause the trailer to pull poorly.  If for pulling reasosns I have to load the Jeep frontwards I will have to get airbags or make my wife take less stuff.  What do you thing will happen, airbags or less stuff?

The Jeep puts less pressure on the floor than a full size horse.  The Jeeps tires are 12.5 inches wide and the contact patch is about 6 inches long with a tread void pattern of 50%.  Now I am just a weather guesser but this is how I figured it, 12.5 inches times 6 inches divided by 2 for the 50% tire void times 4, that is about 25psi for a 3700lbs Jeep.  Now I have no idea how to figure out a horses psi but from having my foot run over by my Jeep, missunderstanding between the driver and me and having my foot steeped on by a 1200lbs horse that did not put all his weight on me, the Jeep hurt far less. I know that is very scientific but that is just the way I am.

 I spoke with one of the owners of Lakota and told him about my plans to use the trailer to move my Jeep around, he did not say anything about that.  I was told that Lakota is entering the toy hauler market so I hope they would stand behind their product. 

I am most concerned about my transmission, I hope it can withstand the HP and the weight, I hope it is not a one or the other kind of thing. 

Using the tire contact patch for a pressure calculation is only good for determining if the tire will pierce the floor.  You are still concentrating 3700 pounds in about a two horse space.  Even two draft horses would be hard pressed to equal the concentrations.  ie... four tires versue eight hooves.

You might want to consider switching your factory transmission fluid to a synthetic based fluid. It will dramatically decrease the opperating temps and increase the longevity of your transmission. You will also be able to drive more miles between your oil service changes.

The synthetic fluid costs are higher than normal fluids, but the payoffs are a longer service life, reduced maintenance and increased transmission reliability.

Synthetics are especially favorable in mountainous driving where your torque converters are unlocked for longer periods of time. When your torque converter slips, the shearing action on the transmission fluid causes an immediate increase in oil temperature. In normal fluids the increased temperature can lead to a pressure and lubrication failure, with your transmission giving up shortly afterward.

The synthetics will all but eliiminate this problem without the added expense of an aux oil cooler.

BOL   Gard

Full synthetic on everything for the last 15 years or so.  It works great.

I will have to ponder on that but my flatbed trailer has a 2"X4"X16' wood deck and has angle iron every 3 feet I know the horse trailer deck is far stronger looking that the flatbed.