Bellhousing ID

[Steve Epps]

Can anyone tell me what range of years this bellhousing was used for ?

GM 3858403

Thanks

-Steve

[Joe L.]

Re: Bellhousing ID

Steve-----

Just down on the thread list someone else asked exactly the same question.

The 3858403 bellhousing was used for a wide array of Chevrolet applications beginning in about 1964, although some may have been used for 1963 applications, too. Basically, there were 2 bellhosuing casting numbers used for most 12-3/4" flywheel applications during the 1964+ period. These were GM #3840383 and GM #3858403. The GM #3840383 casting was used for bellhousing PART number GM #3840381 and, likely, others, too. The 3858403 was used for bellhousing finished PART numbers GM #3858401 and 3858403. All of the bellhousing part numbers that I mentioned are very similar and, for the most part, are interchangeable.

The 3840383 and 3858403 are very similar castings. The differences involve the presence or absence of bosses on the upper portion of the bellhousing for use as the inner mount for the clutch cross shaft. The 3840383 has no bosses. The 3858403 is seen in a variety of configurations. Some have a boss only on the left side which may be tapped or untapped. Some have bosses on both sides. I've never seen the right side boss tapped and I have no idea why it was added to some of these castings.

The 3858403 was used widely in Camaros, Chevy IIs and Chevelles in the 64+ period. As far as Corvettes go, it was used alternately with the 3840383 for most 64-68 Corvette applications except L-36, L-72, L-68, and L-71. The vast majority of these 64-68 applications used the 3858403, but the 3840383 was used somewhat, mostly during 1964-65. For a Corvette, the cross shaft boss is unused and either bellhousing will work just as well. In fact, I don't know why they ever used the 3858403 for Corvettes since it usually involved a drilled and tapped boss that was unused and unneeded but which, presumably, represented a cost to GM to put there.

The 3858403 was used a VERY limited amount in Corvettes from 1969 to 1972. It was used in 1969 with L-88 and 1970-72 with ZR-1. That's it. It was not used in Corvettes after 1972.

[John H.]

Re: Bellhousing ID

Joe -

Here's another obscure usage for the 403, along with the answer for why they had the boss on the passenger side; they were used on right-hand-drive '65-'66 Chevy II's (with the passenger-side boss tapped for the cross shaft bracket attachment and the window cut out on that side for the clutch fork); no, you won't find that usage in the P&A - they were modified at Engineering, who supplied them to Willow Run.

If you wanted to see "Rube Goldberg" at work, you should have seen the mass of linkage rods, bellcranks, brackets, pivots, clevises (clevi? )and weird-looking hardware (hand-made parts supplied by Engineering) required to transfer "three on the tree" shift linkage motion from the levers on the right side of the lower steering column (mounted on the right side of the car), across the dash and down to the left side of the Saginaw 3-speed transmission shift levers. Never did get one to shift at the end of the line - took about an hour's work in Final Process on a lift to get it all adjusted. All were bought by the Government and went overseas to Africa somewhere with huge "Hands Across The Sea" decals on the front doors

[Joe L.]

Re: Bellhousing ID

John-----

The thought crossed my mind that the right side boss might be for a right hand drive application. Then I thought, nah, that's too crazy to even suggest as a possible reason for it.

[Steve Epps]

As always THANKS for the INFO !! *NM*