Disc question

72bluNblu said
We’ve had this conversation before. What you’re suggesting makes no sense from an engineering or production standpoint, because some of those parts would have needed to have been produced for only a 3 month run.

Never mind that there’s a long, fairly well documented history of Ma Mopar running the previous model years parts until they ran out if they weren’t specifically cosmetic model year changes. Hell my August built ‘72 Challenger has a whole bunch of “1971 only” original parts on it.

Still, if you want to show me a 9” spindle or 9” hub and drum assembly that uses large wheel bearings I’m game. Or even a 10x1.75” drum assembly with large wheel bearings. Until then I’m going with logic, documented past practice and the TSB.

First of all, they didn't make a 10 X 1.75 front hub and drum assembly, but that's beside the point of this discussion. As I've mentioned before, there are no before and after dates in any factory manual showing different drum brake spindles used in a '73 A-body. So, only one spindle (3402739) means only one ball joint and one set of bearings. The '71-2 9" front hub and drum is a 3580702 made by Budd and uses the small bearings (A1 and A4). the '73 9" hub and drum is a 33699574 and uses the big bearings (A2 and A17). I know this form owning two of those early '73 A-bodies with 9" front brakes. At the time I parted them out (both rubber floor mat cars with totally rusted out floors) 35 +- years ago, they were both virgins. Nothing had been messed with. At that time, there were still quite a few of them running around here as daily drivers, and those front hub and drum assemblies were gold, as most people weren't looking to convert those cars to disc at that time. Those drums were the first thing sold off those cars. It was a surprise to me when I first encountered them too. After all my research, I discovered how unique they were and that even though they were 9' brakes, all the other attaching parts were the same as the 10" drum and disc brakes. That came in handy when I sold a later disc brake setup off say a '73-4 E-body or later F body to someone putting them in an A-body and needed the upper control arms. The service bulletin I've seen posted only mentions going from 9" to 10" in December, not that they changed from the '72 and earlier parts to '73-up parts. It wouldn't be the first time that Mopar designed and made a part only to change their mind and make something different a short time later. A case in point is the early vs late '66 Barracuda grille emblem. They tooled up to make a V emblem to fit the new grille that year only to decide a couple of months later to make the fish version. There are other examples, but, this diatribe is getting long enough. In closing, just look at all the factory '73 manuals and even aftermarket ones for bearings and ball joints. You will see only one listing for both on a '73 model.