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Hi, Everyone
Could anyone tell me if this would be the correct casting and date of the 3840383 bellhousing for a February 28, 1964 corvette.
Jaime-----
Yes, it's a correct casting and correct bellhousing for a 1964 Corvette. As far as the date goes, the date on this casting as represented by the dots in the right hand bisected circle MAY BE February, 1st week. Or, it might mean something else. There's quite a bit of uncertainty with these bisected circle dates. I don't think they are judged.
I believe that the 3840383 was a one year bellhousing, 1964, but I am not 100% sure. According to my notes I have (or maybe had) 3840383 bellhousings with different Casting information formats:
1. Large "GM" on the top, then "3840383", then 2 bisected circles with the number "12" on the top left circle (for December???), then a large number "1".
2. Large "GM" on top, then "3840383" with a molding line surrounding this number. There are no bisected circles. Bosses on both sides, threaded hole on driver's side, no holes on passenger side.
Your bellhousing is different because the "3840383" casting number is below the bisected circles.
Dave
Last edited by David L.; February 1, 2011, 02:39 AM.
I believe that the 3840383 was a one year bellhousing, 1964, but I am not 100% sure. According to my notes I have (or maybe had) 3840383 bellhousings with different Casting information formats:
1. Large "GM" on the top, then "3840383", then 2 bisected circles with the number "12" on the top left circle (for December???), then a large number "1".
2. Large "GM" on top, then "3840383" with a molding line surrounding this number. There are no bisected circles.
Your bellhousing is different because the "3840383" casting number is below the bisected circles.
Dave
David and Jaime-----
I think the 3840383 was primarily a 1964 piece although I believe its use could have carried over into 1965, too. The 3840383 casting was machined into the bellhousing known as GM PART #3840381 and, possibly, other bellhousings. The GM #3840381 was discontinued from SERVICE in January, 1965 and replaced by the GM #3858401. I do not know what casting number the 3858401 used but it must have been either the 3840383 or the 3858403.
In any event, the 3858401 was replaced by the 3858403 in June, 1966 and, obviously, the 3858403 casting was used for the 3858403 casting. So, under any set of circumstances, the 3840383 casting did not live a very long life.
As far as the configuration of the various casting numbers, marks, etc. are concerned, keep in mind that these bellhousings are a permanent mold casting. Given the number of these pieces that were required during the 1964-65 period, there must have been a large number of molds used. It's very possible that these molds varied with respect to features like the casting numbers and marks. Which mold served as the "progenitor" of the bellhousing used on any particular car would have been strictly the "luck of the draw".
By the way, Jaime, what is the configuration of the bellhousing with respect to bosses or lack thereof on the sides of the upper portion of the bellhousing? If present on one or both sides, these bosses may or may not be drilled and tapped for 7/16-14 which were used for clutch cross-shaft ball studs for some non-Corvette applications.
I will post some examples of what I'm talking about in the next post.
Here are the variations I described. You will note that the 3840383 has no bosses on the upper portion of the bellhousing and this is what I would expect for an original bellhousing used on your 64. However, it is possible that a 3840383 could have been used which had a left side only boss. I have seen 3840383 bellhousings with the left side only boss and I believe these could actually have been used on original 1964 model year cars, although, if so, likely later build cars.
I have never seen a 3840383 with bosses on both sides but I do not rule out the possibility they exist.
The bosses are seen just below the second row from the top of the bellhousing mounting holes.
My 1965 Chevrolet Parts Catalog (effective Oct. 1964) lists GM # 3840381 for 64 PASS., CORVETTE (exc. 409) and 64 TAXI (230)(1st design) and is described as "HOUSING ASSY., clutch (Ident. No. 3840383)". GM # 3858401 is listed for 65 PASS., CORVETTE (283,327) and 65 PASS (230)(exc. TAXI, H.D. Clutch) and is described as "HOUSING ASSY., clutch".
My 1965 Chevrolet Parts Catalog (effective Jan. 1965) lists GM # 3858401 for 64-65 PASS., CORVETTE (exc. 409) and 64-65 TAXI (230) and is described "HOUSING ASSY., clutch (Ident. No. 3840383)". Also listed is GM # 3841551 for 64-65 G10 with the same description as above. GM # 3841551 has the same "3840383" but must be machined differently to fit the truck application.
I believe the reason why these 3840383 bellhousings are so common at the swap meets is that they were also used on 6 cylinder M.T. Chevrolet passenger cars in 1964 and probably 1965. I remember that there were a lot of 64 & 65 Chevrolet 6 cyl. models w/M.T. and that the 64 & 65 Chevrolet 8 cyl. models w/M.T. were quite rare.
In my Chevrolet Parts History manual the part number change you refer to is shown as "3858401 MIX 3858403 06-66". I believe the word "MIX" means simply a part number change without any physical change to the part. On the first page of the Chevrolet Parts History manual "MIX" means "Parts transferred" and "USE" means "Parts Substituted". When an actual physical change is made to a part the word "USE" is used in the Chevrolet Parts History manual as in "3840381 USE 3858401 01-65".
Do you have any thoughts on the terms "MIX" and "USE"?
I have a 3840383 bellhousing with bosses on both sides. The boss on the driver's side has a threaded hole but the boss on the passenger side does not have a hole. The casting format is "GM" and "3840383" with a molding line around this casting number and without any bisected circles.
This 3840383 bellhousing issue is more complicated then I could ever imagine.
Dave
Last edited by David L.; February 1, 2011, 02:45 AM.
My 1965 Chevrolet Parts Catalog (effective Oct. 1964) lists GM # 3840381 for 64 PASS., CORVETTE (exc. 409) and 64 TAXI (230)(1st design) and is described as "HOUSING ASSY., clutch (Ident. No. 3840383)". GM # 3858401 is listed for 65 PASS., CORVETTE (283,327) and 65 PASS (230)(exc. TAXI, H.D. Clutch) and is described as "HOUSING ASSY., clutch".
My 1965 Chevrolet Parts Catalog (effective Jan. 1965) lists GM # 3858401 for 64-65 PASS., CORVETTE (exc. 409) and 64-65 TAXI (230) and is described "HOUSING ASSY., clutch (Ident. No. 3840383)". Also listed is GM # 3841551 for 64-65 G10 with the same description as above. GM # 3841551 has the same "3840383" but must be machined differently to fit the truck application.
I believe the reason why these 3840383 bellhousings are so common at the swap meets is that they were also used on 6 cylinder M.T. Chevrolet passenger cars in 1964 and probably 1965. I remember that there were a lot of 64 & 65 Chevrolet 6 cyl. models w/M.T. and that the 64 & 65 Chevrolet 8 cyl. models w/M.T. were quite rare.
In my Chevrolet Parts History manual the part number change you refer to is shown as "3858401 MIX 3858403 06-66". I believe the word "MIX" means simply a part number change without any physical change to the part. On the first page of the Chevrolet Parts History manual "MIX" means "Parts transferred" and "USE" means "Parts Substituted". When an actual physical change is made to a part the word "USE" is used in the Chevrolet Parts History manual as in "3840381 USE 3858401 01-65".
Do you have any thoughts on the terms "MIX" and "USE"?
I have a 3840383 bellhousing with bosses on both sides. The boss on the driver's side has a threaded hole but the boss on the passenger side does not have a hole. The casting format is "GM" and "3840383" with a molding line around this casting number and without any bisected circles.
This 3840383 bellhousing issue is more complicated then I could ever imagine.
Dave
Dave-----
Yes, I do have some information regarding the connotations of the terms "MIX" and "USE". I believe that what was actually originally intended by the term "part transferred" as applied to the definition of "MIX" relates to the transfer of a part from one GM division of old to another. In this regard a part might have two part numbers. For example, a part might have a Delco Remy part number of, say, 1937241 and a Chevrolet part number of, say, 3793412 (neither are real part numbers, just used for the example). These parts are absolutely identical but are just known as two different part numbers. At some point, GMSPO decides that they only want to carry the part under one part number. So, the 1937241 is "transferred" to become the 3793412 (or vice-versa)and the term "MIX" is used.
Over time I believe the use of the term "MIX" came to be more loosely used for parts that had both FORWARD and REARWARD compatibility even if they were not actually identical. When the term "USE" or "TO" is applied to a part it only indicates that the part has REARWARD compatibility. It does not mean that the replaced part necessarily has FORWARD compatibility. In this sort of situation if the term "MIX" was used, an older part number might get sold for use on a later application and it might not work for that application. In fact, at times I think that the term "MIX" was occasionally applied to replaced parts that did not have FORWARD compatibility and this caused problems.
I think GM finally realized that using the term "MIX" could cause problems in some situations and so the practice of using that term for certain replaced parts was abandoned. I think that the last used of the term "MIX" applied to replaced parts was about 1971. After that time, only the terms "USE" or "TO" and "DISCONTINUED" were used.
This is the configuration 3840383 that I would expect to find on original 1964's. However, as I mentioned, I don't rule out that some used the version with the left side upper boss.
Thanks Everyone
Alan thanks for the pictures, Everyone has been a great help. I have had my 64 for about 23 years know. I have been slowly trying to confirm all the parts that are on the car for originality. I have the Judge Guide, Assembly manual, shop manuals, corvette resto. buy Noland Adams, Fact book buy M.F. Nobbins and etc,. Some things you just cant find in the books. It's great to know there is a bunch Guys with the same love for the Vett as I have.
Jaime
3840383 bellhousing Question
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