I started a thread some time ago, asking for some advice on how to disassemble the tumbler from the chrome button on my 560 SL, which was missing the stainless cap and 'door' on the end http://www.peachparts.com/shopforum/tech-help/211492-any-lock-tumbler-knowledgeable-guys-here-post1753949.html?posted=1#post1753949

As it happened, I got the advice I needed and logged in after I had already completed the job. Sigh.

Anyway, here's a how-to for anyone with a similar problem, or need to remove the lock tumbler from the button:

1. The button assembly is accessed from inside the trunk, visible after removing the latch assembly (3 screws) and the carpeting. Remove the screw attaching the plastic end piece to the vacuum pull rod, then the 2 8mm bolts holding the button housing to the trunk trim piece. Be very careful not to drop any of these into the recess at the back of the trunk.

2. On the workbench, use circlip pliers to spread the clip holding the black plastic piece to the lock tumbler. Then, using a sharp tool like a dental pick, work around and remove the large clip holding the lock tumbler barrel spring retainer in the casing (spring and clip just visible in pic 1 on the left).

3. Now for the trick part, removing the tumbler from the chrome button housing (shown in pic 1). Insert the key fully, and turn it (right, I think) a bit while pushing on the end of the tumbler and pulling with the key. You will feel it start to move out. After it is out about 1/8" or so, the pictured little ball bearing will fly out of the hole in the button casing, from the pressure of the little spring (pic 1, just below the button barrel).
Mine went somewhere, so I used the one from the donor tumbler I had. If you are aware of this, you'll put your finger over the hole while pulling the tumbler out!

4. I removed the stainless cap with the keyslot, the little flap 'door' that covers the slot when not in use, and the rod with the 2 little springs that keep the flap door tight against the inside of the cap, from my donor tumbler/button (from a W126 380SE trunk incidentally, which also shares the door handle with the 560SL).
The procedure to insert these pieces is quite tricky, took me about 6 tries and 3/4 hour, including time to locate flying pieces. The spring and rod go in first, then you have to position the flap door in its recesses under the spring's pressure, and then the cap to hold it all in place. I used a steel rule to hold the flap in, then a screwdriver through the cap slot, exchanging pressure from the rule to the screwdriver as I slid the rule out and the cap into place.

5. The donor cap was held on to the tumbler with 2 tabs. I suspect the cap on my SL tumbler was peened into place around the edge, judging by the 4 tiny indentations around the rim. So, I cut the tabs off and ground the edge down a bit to nearly match the tumbler rim depth, then with the whole affair in the vice, peened 4 new dents to secure the new cap in place. Pic 4 is blurry, but you can just make out the indentations.

6. I should mention that I left the key in for most of the work. When it needed to be out, I taped over the tumbler to keep the pins in place. The tumbler goes back in by inserting the key, aligning the 2 holes, inserting the spring and ballbearing, then push the ball in the hole while pushing/turning the tumbler into the button barrel.

7. Installation is the reverse of removal, of course. The end result was worth all the effort, as I can continue to use the same key as the doors and ignition, and no longer have an unsightly 'capless' button (which looked just like pic 2 sans flap piece). Now if I could just locate a nicer, not-so-pitted trim strip.....for a reasonable price....

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1986 560SL
2002 Toyota Camry
1993 Lexus