I am working on the 1977 Gran Fury 2 door, my drivers door will not open or unlock if the manual lock button is used to lock the door. It takes 10 or so minutes of using the key, wiggling the latch handle, and pulling up repeatedly on the lock rod before the door will open again. This has happened to me twice, the first time I was lucky enough to be in the car. And with my limited mobility, and fluffyness, I am not Dukes of Hazzarding out the window. So it was a 5 or so minute ordeal getting myself out the passenger side while holding a dog leash in one hand.

SO... I have been searching for a 2dr latch to clean and work over on a bench before taking the car in to have it replaced. But the only latch in me price range was a used front drivers door latch, which has a slightly different lockrod actuator location, I figured I could either transfer from my existing if it was serviceable, or modify/fab a lockrod.

But the other option here is to just not have an interior door lock. Just delete the lock rod from the equation. As that is the only item that has caused an issue.

I can use the door key to lock and unlock the door. It works flawlessly as long as no one touches the inside door lock.

Is there any reason why removing the interior lock option would be an issue?

Can't think of one. but removing the door panel may expose the problem with the rod

You can test everything on the door locks and latch with the door open. Makes things a lot easier when you can watch it function, or not function. All you have to do is slide the lever that locks around the door post toward the outside of the door. The biggest issues with old door locks and latches is old dried latch lube. Mopar used the old white lithium grease on the older door latches. Over time the lube dries out and becomes contaminated with dust & dirt. Cleaning them out and re-greasing them often solves many problems with the latches. You may have to pull the latch out of the door to clean and lube it.

Both outside handle and the inside handle should be able to release the latch. Sometimes you need to use a screwdriver where the post would be and pull the lever open. If the lever moves hard with both handles, the latch might simply need to be lubed.

If the outside door handle doesn't fully release the latch, the rod that goes from the latch to the handle has an adjustment. There is a joint on that rod with an Alan head set screw holding the rod in place that would often get out of adjustment. There is a small slotted hole you put the Alan wrench into to loosen the screw to adjust the rod. Usually the rod slides outward making it too long and the handle doesn't lift the3 rod enough to fully release the latch. if that is the case, you loosen the Alan set screw slightly, push the door handle fully down, and tighten the set screw. Then test again. If the inside handle doesn't open the door, the rods between the handle and the latch is probably bent more straight. I will need to be re-bent, the inside panel needs to come off to do that.

With the door open, the latch closed, and the door locked with the inside rod, the inside door handle should be able to open the latch (on the drivers door, might not work on the passenger door, I'm not sure what year the passenger door latch changed). Does the inside handle unlatch the locked door latch?
If you adjusted the outside handle, the outside door key lock may work as well. The key locks are a bit more tricky. The key has to lift the rod up past the movement inside the lever. Any wear on either end of the rod, or any wear on the handle rod hole or the latch rod holes can be the problem. There are also plastic pieces that hold the rods to the lever pieces with the holes, those too can be the problem. Then there is always the possibility the rod that has several bends in it could have been pulled straight at any of the 3 or4 bends. Either of the levers could also be damaged, or the latch itself could be defective.

This will really help, I have a FSM but I didn't see information of the adjustment you mention, But I have not yet studied it in detail, but skimmed and looked at pictures to try and figure out what part does what.

The only thing I have to double check is this... With the door open, the latch closed, and the door locked with the inside rod, the inside door handle should be able to open the latch

I do not recall any of my vehicles doing this prior to the 80's

My 76 Fury (B body), 68 Polara, 75 W250, that didn't work. If the drivers door is manually locked, the inside handle doesn't open the door.I dont think I ever recall trying in my 78 Fury wagon. But the others I would have locked the door placing my arm on the window ledge in warm weather, Get to the place I was going, and look like an idiot for a few seconds until I realized the lock button had been pushed.

I plan to have the latch assembly removed and sonic tank cleaned, then re-lube.

Hopefully it will just be a clean and put it back procedure, but if not I wanted some ideas to fall back on while I wait until a good 2 door latch surfaces that hasn't been priced like gold.

So, this probably won't help, and may add to the confusion, so feel free to ignore this post completely.

A 78 "C: body may not have had the handle adjustment. I've had so many of these out of cars, I forget what had what. Open your door and look at the area the post enters the door. If your door has a handle adjustment, there should be an oval shaped hole at an angle to straight up and down, just above the post area, and towards the outer edge of the door. That oval shaped hole is about 3/16" across and maybe 3/8" long. It may be very close to the outer edge of the door (like 1/2" away from the outer edge.) If you post a picture showing about 6" of height and full width of your door where the post cutout is, I can tell you by looking if you have a outer handle rod adjustment or not.

This is a driver door latch from an 88-96 Dakota. Your latch assembly probably doesn't look the same, there was a lot more space for a latch on a "C" body. I don't have a picture of the rods and they are now inside of the door.
4 pictures.
1) So this is the Dakota door latch out of the door. Its hard to read the writing, but each lever with its color coded rod lock is marked as to what it does. The top of the pic is the top of the latch assembly as positioned in the door, this picture would be taken from inside of the driver side door, looking towards the rear of the vehicle. The right side is towards the outside, and the left is towards the inside of the vehicle. The "rod locks" are the plastic pieces that hold the rods to the levers.

The 1st two listed rod locks would be towards the outside of the door.
The white plastic (lower) rod lock is the outside door handle, it would move up to unlatch the door. If you have the adjustable rod, it would connect between this white clip and the door handle.
The yellow plastic (upper) rod lock would be for the outside door lock. It would move upward to unlock the door, and downwards to lock the door.

These next two listed rod locks would be towards the inside of the door.
The red plastic rod lock is for the inside door handle. As the picture sits, this rod would pull towards you to open the door.
The green plastic would be the inside door lock, As the picture sits, this rod moves down to lock the door, and up to unlock the door.

picture 2) This is the latch in the same positions, just more clear but without the wording.
picture 3) This is the latch as it would sit attached to the door, if you were looking at it from inside of the vehicle, through the door panel, and the steel door frame.
Picture 4) This is a bit more complex. The reason I have these pictures is because these door latches were taken out of a 96 Dakota and put into a 49 Dodge pickup. There is a build thread on that truck in the street rod section, I do not intend on covering that all here. The donor Dakota was a 44,000 mile rust bucket. In this picture I have cut a hole in the 49 door to install the latch assembly (its bolted into place in this picture) and I have cut a hole in the outer sheet metal to mount the Dakota outside door handle (the black piece of metal I'm holding). You are looking through the original hole the Dakota outside door handle was in. As a note in point, on the Dakota, this handle hole would have been another inch higher on the outside door skin, but compromises had to be made, the 49 door is 1/2" more narrow then the Dakota door, and the latch was put in at the doors widest point. The 49 door narrows more as it gets towards the top. On the Dakota door, the outside handle would have been above the door latch.

What it does show very clearly is how the latch assembly is in the door.
The rusty channel running up and down through the door on the right side of the hole is the window track. It can not be moved. Both the Dakota and the 49 had a channel like this. The door glass slides up and down from the channel and would separate everything between inside and outside on the door, to the left of the channel.
To the right side of the window channel are the two levers for the outside door handle (lower white plastic rod lock) and the outside lock (upper yellow plastic rod lock). Both are on the outside of the window. The lever in the Dakota handle would have been connected to the white (lower) rod lock, and lifts that lever up to open the door (I had to bend a new rod). The door lock on the Dakota it inside of the handle, it would lift the rod and lift the yellow plastic rod lock lever to unlock the door and would have had to push both down to lock the door. On the 49, the door lock itself didn't clear the door glass.

To the left of the rusty window channel you can see the inside door handle green plastic lock rod lever, the inside lock lever is above it and is covered by the sheet metal I'm holding. Both of these levers are inside of the glass. The green plastic rod lock lever would move towards the left to open the door.

The latch assembly in your "C" body probably doesn't share the same space as the window tracks, but the inside rods and levers and the outside rods and levers still have to be on the correct side of the glass. Hopefully this helps and doesn't add to the confusion.