M Series Door Latch Repair

majortom

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Aniwa, Wisconsin
The following information is how to repair the common failure of the door latch mechanism used on M series 2 1/2 , 5 & 10 ton trucks is also applicable to M37 Dodge.

We get many calls for door latches due to internal failure causing the outside handle not to function. The left latch is very hard to find and is not interchangeable with the right hand latch. The latch is the same for all of the above mentioned units except for the length of the arm to the inside handle.
Yesterday the latch failed on my truck. But I couldn't just replace it I had to know why. After disassembling the latch, the failure was obvious. The quick fix was also obvious.
How the latch works: After you rotate the outside handle it rotates a cam, that pushes a lever attached to the striker. What happens with use is the clearances increase enough so that the cam will slide under the lever and the outside handle does nothing. To repair the problem you must remove the latch from the door. With a firm tap on a specific spot with a punch and hammer on the striker lever the latch will work just like new.

Pic 1: Shows Left Hand Latch

Pic 2: Shows The Exploded View From Left To Right Latch, Cam, Cam Retainer & Cover.

Pic 3: Shows a that the cam has slide under the lever (Broke).

Pic 4: Shows the striker held in the open position with a vicegrip to gain access for the bending operation.

Pic 5: Has the cover removed so the part striker lever being bent

Pic 6: Bending the lever using a punch or chisel with a hammer. Give the punch several good raps then insert outside handle in latch checking for proper function, repeat as necessary.

Pic 7: Shows the cam resting against the striker arm in the proper position with the cover removed.

Pic 8: Shows the cam rotated to the open position.

In short you do not have to take the cover off the latch to repair it we did that to give a better understanding of the inner workings of the latch. One of the easiest things I have ever fixed on a Deuce.

Time to complete Procedure: Half Hour
Materials: 0
Beer: 2
 

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chris10980

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Stony Point, New York
While on the subject of door latches, has any one replaced the door handle with one of the locking versions found in the Grainger or McMaster Carr catalogs? If so which one did you use?
 

Amer-team

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Centralia/WA
Thank you for the excellent pictures in this thread. The repair did not take long, but I did not anticipate taking the door handle assembly out of the inside too. Once it was figured out that it all came out together, it did not take five minutes to do the repair outlined in the pictures. Liberally lube the whole mechanism up and put it back in place.
I had previously moved the exterior door handle to the horizontal position, that made it easier to grasp, as opposed to the vertical hanging down position. What I wonder is if this did not make the mechanism more susceptible to higher force when being pulled down. This could have aided the problem of the interior piece being bent and not functioning. Anyway, moved the handle back to the vertical position. Thanks again for the help.
 

olly69

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Location
Cuba, New York
Thank you for the excellent pictures in this thread. The repair did not take long, but I did not anticipate taking the door handle assembly out of the inside too. Once it was figured out that it all came out together, it did not take five minutes to do the repair outlined in the pictures. Liberally lube the whole mechanism up and put it back in place.
I had previously moved the exterior door handle to the horizontal position, that made it easier to grasp, as opposed to the vertical hanging down position. What I wonder is if this did not make the mechanism more susceptible to higher force when being pulled down. This could have aided the problem of the interior piece being bent and not functioning. Anyway, moved the handle back to the vertical position. Thanks again for the help.
OK, great write up, but can you help this newbie? How so you get the whole mechanism out to start with? Do you reach up thru the access window on the bottom of the inner door? Help!
 

blisters13

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Beaumont in SoCal
I had to do this job; I bought a new (probably Chinese) latch and it only lasted about 25 - 30 operations before the outside handle would not operate the latch.

Took me about fifty minutes from walking outside to the truck to having all the tools put away.

My assembly had no lube on the two middle parts shown in the second picture in the OP; taking the cover off allowed adding some grease, as well as getting a better angle on the tip to punch it down. Also, I bent the index tab of the cover (up by the square hole, which indexes into the main frame) to tighten-up that whole part of the assembly as the three moving parts were pretty loose.

No beer this time.

Works flawlessly now.

THANKS MajorTom :goodjob:

-Ken
 
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