GM part #'s; change from 7 to 6 digits

[Wayne M.]

When did this practice begin ? I suspect early '70's [my "newest" P&A is Jan 1970, and all that I look at are 7-digit]. Where does one find the parts # cross reference ?

Example: an eBay 10_13/32" dia clutch disc , NOS in box # 458629; my books show two possibilities in Gr 0.886, #3927128 and 3886059.

[Duke W.]

Re: GM part #'s; change from 7 to 6 digits

In the early seventies GM realized that they were running out of 7-digit part numbers. To buy a little more time before the 8-digit system came into being, they gathered up all the unused 6-digit numbers that had been allocated to various divisions going back to probably the pre-WW II time frame.

So a lot of parts released in the early to mid-seventies have 6-digit numbers. This is the case with many Cosworth Vega specific parts since these were all released in this time frame.

At this point, I expect most of these 6-digit numbers have been discontinued or superseded by 8-digit part numbers.

I think there are some commercial cross reference books out there, but I don't think GM produced them.

Joe L. can usually provide a complete part number history for a specific part - the original released part number, subsequent numbers, and whether the last part number is current or discontinued.

Duke

[William C.]

Re: GM part #'s; change from 7 to 6 digits

We were using 7 digit numbers in the early 60's at my facility, and I started in 1963. They had been around for a while at that time... 6 digit #'s were early-mid 50's and before. We still made some of the old parts using the original numbers. 458629 does not show in my'72 price book for Chevrolet nor my '51 Chevy parts master catalog. all the disks in the chev line were 836 or 837 startin numbers in the early 50's and prior, although some of the parts had been superceeded by seven digit replacements by '53, so the seven digit numbers were being used in early '50 .

[Joe L.]

Re: GM part #'s; change from 7 to 6 digits

In the early seventies GM realized that they were running out of 7-digit part numbers. To buy a little more time before the 8-digit system came into being, they gathered up all the unused 6-digit numbers that had been allocated to various divisions going back to probably the pre-WW II time frame.

So a lot of parts released in the early to mid-seventies have 6-digit numbers. This is the case with many Cosworth Vega specific parts since these were all released in this time frame.

At this point, I expect most of these 6-digit numbers have been discontinued or superseded by 8-digit part numbers.

I think there are some commercial cross reference books out there, but I don't think GM produced them.

Joe L. can usually provide a complete part number history for a specific part - the original released part number, subsequent numbers, and whether the last part number is current or discontinued.

Duke

Duke and Wayne------


Yes, this is pretty much how it was. Most 6 digit part numbers date back to a "prehistoric" GM period. However, beginning in late 1972 GM salvaged several blocks of un-used 6 digit numbers and assigned them to parts released in the 1972-78 time period for the reasons Duke described. As far as Chevrolet goes, these part numbers were in the 3xxxxx and 4xxxxx series. I believe that Chevrolet was the primary "needy" division, though, because I don't think the others had run out of their 7 digit part numbers. As a matter of fact, Cadillac was still assigning part numbers from their 35xxxxx 7 digit series' well into the 90's.

I think that Rochester was the first GM division to start using the 8 digit part numbers and that began about 1974 or 1975. Chevrolet 8 digit part numbers began in the 1978-79 time period with the series 14xxxxxx.