not sure if the two plugs were installed when the axle housings were painted. BTW, were u all aware of why the 57 axle housings had a drain plug and the 56's did not? apparently, there were quite a few 55 and 56 differentials that made excessive howling noise when new and chevy's fix included replacing numerous ring and pinions in the 55 and 56 pass cars under warranty. . the noise peaked at 55 mph on power glide pass cars. to eliminate the problem in 1957, chevy used a special break in oil that was to be drained at 1000 miles. that is why the 57 up axle housings had a drain plug. i got this info from an elderly chevy mechanic whose opinions i take to the bank. anyway, what u all think about finish on 57 fill and drain plugs. mike
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Re: finish of 57 differential fill and drain plugs
Mike, I see the '56-'57 JM has no info re plugs, but are there any photos of the underside/axles in Noland's book that might help, albeit B&W photos? Mine's not handy at the moment.
My WAG is painted so the paint wouldn't get inside the plug threads or deep inside. But maybe they did coat the threads for better seal?
Interesting info re the warranty work and the '57 drain plugs.
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Re: finish of 57 differential fill and drain plugs
good idea rich, but no lands photos are definitive re finish of plugs. regards, mikeComment
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Re: finish of 57 differential fill and drain plugs
Mike, I just looked in Noland's book(RIP Noland and thank you).
Page 135 has a '57 chassis shot after driving on the proving grounds, but not really showing enough detail. I scanned it in hi-resolution then cropped it, below. Can't tell if it's mud, or bare, or rust or paint, sorry.
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Re: finish of 57 differential fill and drain plugs
Rear axle housing print (10-16-62) shows plug 3686529/344829 (optional part #s) as part of an assembly that was to be welded to housing at point of fabrication. One could assume plug would go along for a ride with the complete Rear Axle Housing.Comment
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Re: finish of 57 differential fill and drain plugs
both plugs dave? thanks, mikeComment
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Re: finish of 57 differential fill and drain plugs
Sometime prior to body drop, the assembled chassis was painted chassis black, right?
If so, it would seem to follow that everything on the rear axle assembly would be black.
Also, it would seem to follow that the plugs would have been installed and received whatever finish was applied after complete assembly at the Detroit Gear and Axle plant prior to shipping to St. Louis.
Now, back to drain plugs. Does anyone know why the drain plug was no longer installed in 62-later models? Remember, the same type rear was continued in pass cars up through 64, and 62-64 pass cars no longer had the drain plug and the housings were still built at the same plant.
On every car I own, when I build a rear, I install my own (magnetic) drain plug----------------------to heck with what's correct!!!
The 56-62 housings (55-64 pass cars) are merely stamped steel. Thus, there is precious little metal for threads and it is somewhat common for the drain hole threads to eventually become weakened to the point that zealous tightening of the drain plug will produce a continual leak. Whenever I have one of these type axle housings apart, I tack weld a nut to the INSIDE of the housing to provide plenty of threads for the drain plug. Then I drill 2-3 holes in the flats of the nut to enhance drainage. No one can see it!
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Re: finish of 57 differential fill and drain plugs
thanks much tom and dave. mikeComment
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