3899621 Bellhousing ID Help

[Dereck S.]

All
I'm looking for some help identifying if the attached 621 bellhousing is the early version as well as what the casting date decodes to. I believe it's early since the GM raised letters are on the side along with the part number and casting info. My guess is it is a 1969 casting date but I'm not clear how to decode it properly. Any help is appreciated.
Dereck

[David L.]

Re: 3899621 Bellhousing ID Help

I believe that the 67-72 3899621 bellhousings have the "GM" on the side. Years ago I had a 3899621 bellhousing from a 1970 Chevelle. According to my notes the casting numbers were very similar to your photo.
a. the large number "5" (exactly like yours)
b. the left circle: the number "5" with 4 dots over the number "9"
c. the right circle" the number "9" over a black space (exactly like yours)
d. "3899621" (exactly like yours)
e. "GM" (exactly like yours)

Dave

[Dereck S.]

Re: 3899621 Bellhousing ID Help

I believe that the 67-72 3899621 bellhousings have the "GM" on the side. Years ago I had a 3899621 bellhousing from a 1970 Chevelle. According to my notes the casting numbers were very similar to your photo.
a. the large number "5" (exactly like yours)
b. the left circle: the number "5" with 4 dots over the number "9"
c. the right circle" the number "9" over a black space (exactly like yours)
d. "3899621" (exactly like yours)
e. "GM" (exactly like yours)

Dave

Dave
Thanks for the response. I've since found other threads that confirms your feedback that the GM logo was on the side of the housing up until 72. The best I could find regarding casting date decode is the 9 means the month or September and the number of dots, 4, means the week or 4th week. Nothing I've read indicates the year of the casting is present. Others might chime in on that conclusion. I thought there was an article in the Driveline years ago. I've not been able to find that.
thanks
Dereck

[Joe L.]

Re: 3899621 Bellhousing ID Help

Dave
Thanks for the response. I've since found other threads that confirms your feedback that the GM logo was on the side of the housing up until 72. The best I could find regarding casting date decode is the 9 means the month or September and the number of dots, 4, means the week or 4th week. Nothing I've read indicates the year of the casting is present. Others might chime in on that conclusion. I thought there was an article in the Driveline years ago. I've not been able to find that.
thanks
Dereck

Dereck------


A reference to year was not provided on these "bisected circle" casting dates. This makes the rest of the information fairly useless for restorers. Keep in mind that the purpose of the date information was for quality control purposes and had nothing to do with accommodating future restorers.

Addendum:

I have observed that, for some unknown reason, GM aluminum die castings rarely include a date with reference to year. Often, there is no date of any kind. On the other hand, cast iron castings, if they include a date at all, usually do include a date with reference to year.All GM foundries were then operated by the Central Foundry Division so I've never understood why there was no standardization on this.