Wanted to share some recent off-line discussions I had with JohnZ regarding a part number change, in this case a 67 RS grille, which I feel is relevant to this thread. I cited a specific example to him but as you will see in the end what essentially came out of the exchange is when the AIM shows a part number change then a part has been removed from service and another new part put in its place with a new part number. That in itself seems straight forward and simple enough, but what is more interesting and what came out of the discussion is if there is a “minor” change made to a part then the drawing is revised and the drawing revision block has a date put in for that change. Below are the exchanges (I’ve shortened and paraphrased my questions to save space):Steve - That's a revision record of a "running change", where one part was cancelled and replaced by another one; there were hundreds of these through the model year. The date in the revision record was the date of the change at Engineering, but the actual effective date in production (on the line) could have been a month or two either before or after the date in the revision block - the effective date was tracked in a different system with an NPC (Notice of Production Change).
Question: So that part number change would mean that there would have actually been a change in the part and not simply the same part but with a different part number assigned to it?
Steve - When a part number changed, it was because the part actually changed to a different part; the previous part was cancelled, and replaced by the new part. Very minor changes in a part were handled with drawing changes, but those never changed the part number.
Question: What about drawing-only changes?
The only way to confirm a drawing-only change is to have the GM part drawing and look at the change history in the revision block; usually the only folks that have the original drawing are manufacturers of GM-licensed reproduction parts.
As those of you that have been following this thread already know the 68 RS center grille (part # 3919060) started the 68 production run with the chrome/silver horizontal bars. No part number change has ever taken place with the grille although the chrome/silver horizontal bars were dropped at some point. Was this a “minor” drawing change? Don’t know, but I intend to pursue this as best I can (I have a GM lead) at the same time we continue to collect actual car data.
We have been successful in obtaining some additional info from one of the other persons that Rich put us in contact with. He actually has two cars and the data he supplied for now supports the theory. His 05 car also had the lower grille to valance screw/u-nut attachments found on Ed’s, Mark’s, and my car which, again if you have been following the thread, is an anomaly to the AIM.
Rich, I'm ready for more contacts if you have some.
Note: See post 154 if you want to add your RS data.