[alfa] Duetto differential

["John Hertzman" <johnhertzman@xxxxxxxxxxxxx>]

 (This is an edited rerun of a post sent previously which disappeared; if it now shows up twice in two versions please accept my apologies.)
 
Alex Swaim, having found a single brass washer after having removed both the fill plug and drain plug from the differential of his Duetto, guessed that the washer went with the fill plug rather than with the drain plug but asked the list whether that was correct. Brian Shorey replied that he thought Alex chose wrong, and believes the washer goes on the drain plug. Russ Neely said it could be either, depending on the designs of the drain and fill plugs, with or without a shoulder, and that some drain plugs have a taper and require no gasket.
 
In the purely English and/or American language parts books these parts are usually called washers, as both Swaim and Shorey did, but in the polylingual or purely Italian parts books they are guarnizione, gaskets, rather than rondelle, washers, a distinction which may help explain apparent discrepancies. Washers and circular gaskets may appear similar, but gaskets normally serve sealing functions only and washers normally serve mechanical fastening functions, which can affect form, proportion, section, surface treatment,and material choices. Different things entirely.
 
Alfa Romeo parts books say that on all 1900, 750, 101, 102, 105, and 106 cars through the 1750 and 2600 there are two different shouldered plugs, (one magnetic and one not) of the same size but with any of four different part numbers, on both the drain and fill plugs on both the rear axles and the transmissions. They all have one or another of four different gaskets sharing a 22.2 mm inside diameter. They all are used in enough different combinations on the various housings that it seems safe to say that all used the same threads, presumably NOT tapered pipe plug threads, which may well have been used occasionally as kludges by mechanics to replace mislaid parts at some time post-production.
 
I can't say what might have been used on later cars, or when, but if at some point new cars came out of Arese (or Turin, etc) with taper-threaded steel pipe plugs in aluminum castings that would be, for me, one more big data-point in the ongoing last-of-the-real-Alfas discussion.
 
Enjoy yours, 

John H.
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