I HAVE A S AND W 39-2 73-74 MFG THE DECOCKER IS INTERMITTANT. INTERNAL PARTS LOOK OK SEEMS LIKE THE SEAR RELEASE LEVER IS TOO LOW, NEED TO KNOW WHAT TO LOOK FOR. ANY IDEAS? THANX JW

You are probably correct. Wear can occur on both the top of the sear release lever, and on the bottom angled face where the lever interfaces with the sear. Barring any other mechanical issues, fitting a new sear release lever will usually solve the problem.
The new lever will need to be fit to the gun as this is not a "drop in" replacement.

Wear on the slide rails can also be a factor. As wear on these rail surfaces increases with use, the slide rides " higher" on the frame. This can effect the interface between the top of the release lever and the safety lever/decocker body.

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Ret. LE, FA Instr, S&W Armorer

Is there a thread on how to fit one?

Perhaps....I haven't actually searched here for info on that specific topic.

If you can find a S&W pistol armorer in your area, they could install the part for you. Or perhaps S&W Customer Service could help out. 1 800 331 0852

Lsg in texas......lsgmfg.com, is an authorized S&W warranty station, and may be able to help.
I believe Frank Smith is still the owner.

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Ret. LE, FA Instr, S&W Armorer

Is there anyone in the phoenix area to recommend? jw

You might try Frank Glenn at glenncustom.com. I believe he still works on the early S&W pistols.

If not perhaps he could recommend someone in the area.

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Ret. LE, FA Instr, S&W Armorer

I found out pressing down on the slide corrects the problem. the movement down is just a few thou. but is just enough to make it work.