Removing passenger side door latch

[Mertz]

I have everything loose trying to get the door latch out to repair a broken or missing spring but it is being held up by the key assembly. I have removed to chrome cover and tried to unscrew it. Not budging and very hard to get a grip on it. I have a key and thought it might release with the key in the correct position but that doesn’t work. There is access to a square shaft in the inside of the door. 1940 Plymouth truck. 
 

Any help would be greatly appreciated. Thanks 

[9 foot box]

   There is a 7/16” hole in the door jamb, below the latch. There is a set screw accessible through that hole that holds the door lock cylinder in. 

[Mertz]

So what looks to be a square shaft is the set screw?

[9 foot box]

   No, but this is where the set screw is. 

[Mertz]

I found the hole but my truck has a much smaller hole and I can’t get a screwdriver on the set screw. I will try to enlarge the hole so I have better access. I tried pounding on the shaft with a punch and moved it out about a 1/4” but that didn’t loosen things up so I pushed it back in. I spayed WD on it and will try again tomorrow. 

[Fiddy B2C]

I had the same problem…I ended up having to drill out the set screw, re-tapped the hole. I fixed the door and got a new set screw.  Now everything works as it should… the only bad thing now is the fact that there is no friggin external key lock on the drivers side and every time you want to lock the truck, you have to slide over and exit via the passenger side…

[Mertz]

Mine being a Montana farm truck I don’t think the lock was ever used. I think I’ll get some reverse drill bit to try to get it out if nothing else works. 

[tonybiel]

The small hole where you see the square shaft is only to aid you with the reinstallation of the square shaft/lock back into the door latch.

 

The larger hole on the end of the door is where you will find the set screw.  The set screw likely requires a hex allen wrench to remove it.  Sometimes, but seldom does a set screw have a screwdriver slot as you mentioned.

 

Because of rusted threads in the door, the set screw on my truck also would not screw out.  My door lock was already not useable and I had found another used one.  So I drilled out the lock from the outside, taking it out in pieces.  Then my set screw easily screwed into the lock chamber.  The threads are less likely to be rusted on the back side.  I was then able to clean out the door threads nicely with a tap.

[Mertz]

Unfortunately mine does have the small slotted screw. I have filed down a screw driver to get a good fit but it is still at an angle because the hole is off center of the screw. I’m going to enlarge the hole and try again. If that doesn’t work I’m off to Harbor freight to get some reverse drill bits. Hopefully the screw will come out without retapping. My lock works with the ignition key and is in very good condition since it was hardly used. I will be replacing the screw with an Allen head to make getting it in much easier. Wish me luck!

[Mertz]

WD40 overnight and drilling out the access hole was a success but I can’t get the latch out because of the window track attachment to the door. It had to go in so has to come out that is if the track was added before the latch mechanism. I’m stumped.