C2 Bellhousing

[Paul G.]

I have a December build 65 365hp coupe which I'm in the process of detailing with the engine and trans out. I'm trying to follow the 65 JG but I'm a bit stumped on the appropriate bellhousing part number. I have what I believe the original bellhousing but it's part number 3840383, the JG calls for 403 only. Since I'm going to have the vehicle judged someday, should I change it? When I searched the NCRS archives, it looks as though many folks who are well respected "regulars" here on this board acknowledge the 383 being used on some 65's. Is there any hope for the JG being changed to reflect this or is it a lack of compelling evidence that this part was actually used in regular production?

[Wayne M.]

383 in '65 L76 # 014xx

and I have no reason it's not original. You may have to take the point loss until sufficient data surfaces to effect an "also accepted" notation in the '65 TIM&JG.

[Joe L.]

Re: C2 Bellhousing

Paul------

I'm a strong advocate of the notion that the GM casting #3840383 bellhousing was used for 1964 Corvettes and, likely, early 1965's, too. Wayne's car is a perfect example of the latter.

To be honest, it surprises me that any 64's are found with the 3858403, although I would not rule out that this bellhousing was used. If so, though, I would expect that such examples would be the exception, rather than the rule.

For 1965, I would expect that early cars could very likely have used the '383' and, perhaps, there would be sporadic use thereafter.

GM parts information indicates that GM PART #3840381 bellhousing (the part number for the bellhousing with casting number 3840383) was used for 1964 model Corvettes. It also indicates that the GM PART #3858401 (the original part number for the bellhousing with casting number 3858403) was used for 1965 Corvettes. However, I would expect that earlier, if not even later, 1965 Corvettes could have received the '383'. BOTH of these bellhousings are equally functional for the Corvette application and are 100% interchangeable. They are virtually identical, too, with the exception of the addition of a boss or bosses to the '403' which are completely superfluous for the Corvette application.

The GM PART #3840381 bellhousing was discontinued from SERVICE in January, 1965 and replaced by the GM PART #3858401. That implies that the bellhousing ceased to be manufactured sometime prior to that date. That's not for sure, since it could have continued to be manufactured for PRODUCTION-only purposes. I strongly doubt it, though. I expect that whatever 3840383 molds that existed were modified to become the 3858403, with the casting number also changed on the molds. However, there was likely a "phase-in/phase-out" period when both bellhousings were being produced.

The earliest that I can find SERVICE availability of the GM PART #3858401 bellhousing is October, 1964. Of course, it could have been used in PRODUCTION prior to that time, but I just really doubt it. Also, consider that the GM PART #3840383 bellhousing was released for the 1964 model year and discontinued as of January, 1965. If, as some consider, it was not used for the 1964 model year, then where did these '383' bellhousings come from? I can see no reason, at all, why the '403' would have been used for 64 Corvettes but the '383' used for other cars. As I mentioned, there was no special feature of the '403' that was EVER required for Corvette applications. And, if the '383' bellhousings were used for 1964, then I believe that they easily could have been originally used for earlier 1965's, as well.

One other thing to keep in mind: as I mentioned, the GM PART #3840381 bellhousing was discontinued in January, 1965. So, any 1964 or early 1965 Corvette that may have been originally fitted with the '383' bellhousing and requiring a replacement for any reason after that time would have received the '403' bellhousing. No one would have cared, or, likely, even noticed that the replacement bellhousing had a different casting number on it than the original. So, what's now considered "original" might not be so original.