I tow a 24 foot 4500lbs travel trailer with my van it isn't fast but it tows it just fine. With a 3:73 rear end and a good trans cooler you can tow a rated 6000lbs with the 3:43 the vans are rated at 5000lbs the max tounge weight is 700lbs. But use a good weight distributing hitch as it will stop the van from getting the bouncies if you hit a dip in the road.
Note sure where you're getting your figures, but reading directly from the owners manual, 3.73 is 5500lbs, 3.42 is 5000lbs, and 3.23 is not recommended for towing. AWD models are approximately 500lbs lower than this.
IMPORTANT: These ratings INCLUDE passengers, luggage, fuel, etc, INSIDE THE VAN. This rating is not just the trailer.
Tongue weight limit has nothing to do with the van itself. It's a limit of your brand of hitch.
There are usually two weight limits printed on the hitch receiver itself, one rating with a WD hitch and one rating without. Basically you can have a trailer that is within the tow weight limit, but if it's tongue weight is higher than your hitch is rated, YOUR OVERLOADED.
The tow rating is only a slight part of what's involved. The wind resistance is a huge part of this limit.....meaning a 15ft flat trailer loaded with 4500lbs of bricks will tow much better than a 24ft 4500lb high standing travel trailer. Add 6 people, a tank full of fuel and a few ice chests, luggage, and a canoe on the roof into the travel trailer scenario, and you're seriously overloaded, even though the trailer is still 4500lbs.
Terrain is also another major consideration. A 4500lb trailer will tow much better through the flat lands of the south than it would through the Rockies.
Believe it or not, altitude is another major consideration if you're regularly towing at higher altitudes.
Rule of thumb is that you loose 10% of your horsepower for every 4000ft of elevation. If you're towing through the Rockies and find yourself at 12,000ft, you're going to be in trouble.
Note: Most people think that the tow limit of a vehicle is directly related to it's power and or drivetrain. While this of course is somewhat correct, a very important item that is always overlooked is BRAKING power. You can soup up the engine, add coolers, gauges, etc, to the tranny, beef up the suspension, etc... but low and behold the brakes are never thought of... until you and your trailer end up in the middle of a field, or much worse.
In summary, ALL vehicles have a rated tow capacity. ABIDE BY IT! These can be found in numerous places on the internet, in your owners manuals, etc. READ THEM CAREFULLY!!
Understand that when you hitch a trailer behind your van and don't take the time to learn what your doing, you take the lives of your family and everyone around you on the road into jeopardy.