If it's what I'm thinking just remove it, clean the screw, put some Permatex #2 on the threads, and reinstall.

If there is oil behind it put your shop vac on the axle vent while performing the procedure, keeps the oil from running out.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-