97 dodge dakota driver door sag, repair.

lubricate all door latches and hinges (GENEROUSLY) with WD 40, repeatedly open and close doors until latches are working good.
After doors are closing as they should respray all latches and hinges with lithium grease. If this does not work replace latches and have door hinge pins checked.
2009 Hyundai Accent grease and lube all latches
How To Fix Sagging Door Replace Hinge Pin Bushings Monte Carlo Grand Prix

If you are lucky, you can adjust at the hinge

you have to mach it up its a maybe

Check for wear on door hinge pins.

The door may be sagging.

May need to repalce the door hinge pins

Removal & Installation

1. Matchmark the hinge-to-body and hinge-to-door locations. Support the door either on jackstands or have somebody hold it for you.
   

2. Remove the lower hinge-to-door bolts.
   

3. Remove the upper hinge-to-door bolts and lift the door off the hinges.
   

Details of a common door assembly-Dakota shown
Click to Enlarge

To install:

1. If the hinges are being replaced, remove them from the door pillar.
   

2. Install the door and hinges with the bolts finger-tight.
   

View of the door hinges-1994-96 Pick-ups

If the door is not latching properly, a torx drive bit will fit into the latch pin itself and you can move it a little further outward. If the door is sagging (don't quote me on this, i'm not real familiar with the model), you may be able to loosen the hinges and lift the door, you may have to replace the hinge pins, or the hinge altogether.

usually the door latch will go bad when the door hinge bushings are very worn. Inspect the door hinge by holding the door a grab the outside door handle and the door shell firmly. Now lift the door up vertically and see if there is any play in the hinges. If the slightest movement is found replace the door hinge pins and bushings. your door latch may work great again If not replace that too

The door hinges have pins in them. The pins have bushings in the hinge. If you go down to your local parts parts store you will be able to purchase them. They are brass colored. You will need to unbolt the doors and use a punch to hammer out the bushings and use a hammer to replace them.

Remember that there is a little play in the hinges, even new ones, enough that just a slight degree of play at the hinge axis will result in several fractions of an inch movement at the latching end of the door. The key here (assuming the lower hinge is still mounted at factory height with respect to latch) is to adjust the angle of the hinge's axis such that the latching mechanism is 1/2 inch higher than the stiker plate BEFORE tightening down the hinge's mounting bolts, then when you remove your support holding up the latch end of the door it should sag back down approx 1/2 inch and line up perfectly with the latch plate. I used to do this on an old '79 Monte Carlo I used to have and even being the smallest of the Monte's, it still had fairly long, heavy doors for back then even and could get the doors to shut/latch perfectly. I own a VUE now-a-days and its door's are featherweights by comparison so they should be fairly easy to adjust and you shouldn't have to tighten the @#$% out of the mounting bolts during the adjustment, just make sure you tighten them good when the alignment turns out correct upon final inspection.
If your adjustment sags again after shutting the door a few times, then you didn't tighten down the hinge mounting bolts enough and will have to go through the adjust procedure again making sure to tighten things up better the 2nd time around.

I don't think the problem is the door latches. Sounds more likely that the hinge pins are gone. You say you have to lift the door and slam it. When the hinge pins go the door will sag and you will need to lift it up to align with the striker pin on the door frame. Get a new set of hinges for your truck.

Hope this helps

Mike