I am looking into possibly upgrading my hitch to a class 4 instead of the 3, is this even possible given our trucks have the crappy 3.0?

 

Depends what you mean. Its possible, sure. You could also put a class 4 hitch on a geo metro. You could also put one on a moped.

Is it realistic is hard to say. Number one Class 4 is 4,000 pounds, so if you are hauling that much, thats pushing not only the engine, but the suspension and brakes of the yota. Anything heavier than 3,000 I like to have a 3/4 ton.

However, it can be done. If the trailer is equipped with trailer brakes, and you are very careful, I would tow 3-4k on flat ground for short distances. However, hilly ground, or long distances, or any distance/grade without trailer brakes, would be a no-no.

Basically I wouldn't do it.

 

that would be scary on a big hill with no trailer brakes

 

Well i am not getting it solely for towing. I am simply using a dirt bike carrier to carry to bikes on my runner. the class 3 hitch only allows 500 pounds at the tongue. I need atleast 650 at the tongue, so I am thinking that a class 4 would allow more than 500 at the tongue

 

so you want to hang that much weight off the back of a vehicle that already has a reputation for saggy rear springs?
Class 4 hitches are usually limited to 600 lbs of tongue weight. Save the money and just buy yourself a small trailer from someplace and haul your bikes with. IMO in the long run it would be the better move.