[John V.]

In this linked thread, in response to MUSLCAH's question, I outlined the standard axle ratio for the '64 Auto Trans Tripower GTOs, including the mid year change.

https://forums.maxperformanceinc.com...d.php?t=852172

I don't know if this is of interest to anybody else, but while looking for info about another '64 GTO, I came across some PHS records that prompted me to start this thread. It has some bearing on my earlier post.

I noted earlier that PMD announced the revised Tripower standard axle ratio and stated that the change was effective with production starting Jan 27, 1964.

My source was the Service Craftsman News although IIRC, there was also a Flash Bulletin that provided the same information.

But I have a couple PHS Production Manifest records from the Pontiac Plant that would indicate the change did NOT occur as early as Jan 27.

Up til now, I have believed that the axle ratio change occurred on Jan 27. At the same time, I have researched various records and concluded that PMD had been including the HD Radiator on Tripower builds at no extra cost (it would not be listed on the Window Sticker) until some time around March.

Knowing that the HD Radiator was required for the 3.55 axle, it was no surprise that PMD chose to include the HD Rad but bury the cost in the Tripower option price.

But when the change was made to the 3.23 axle, it surprised me to see that the HD Rad continued to be included for the Tripower. I surmised this from KC & Balt PHS records that reflect the Rad Code. The HD Rad codes were found on some builds at no extra cost after Jan 27 so I concluded PMD had changed the standard axle ratio but for a time failed to discontinue the HD Rad as standard.

I now believe I was mistaken in this conclusion based on a couple Pontiac Plant records I have just reviewed.

One record is for a Tripower GTO with a Production Date of Feb 3. It includes the 3.55 axle ratio but does not show a Special Order axle approval. Whenever a Special Order axle ratio was included the Manifest always shows the requested gear combination and notes the Approval.

Since no approval is noted, it means the 3.55 axle was the standard release.

The HD Rad was required with the 3.55 but it is not marked as an option on the Manifest, so it was included at no extra cost on this build.

The 2nd record is for a Tripower GTO with a Production Date of Feb 6. It also includes the 3.55 but no Special Order axle approval so again, this build got the 3.55 as the standard release.

And same as the previous one, the HD Rad wasn't marked as an option, so it was included at no extra cost on this build.

I also reviewed two other Pontiac Plant Manifest records that show that the HD Rad had become an extra cost option for the Tripower.

The first has a Production Date of Mar 2, the 2nd has a Production Date of Mar 6.

Both got the Special Order 3.90 axle ratio and both show the Sales Code 432 HD Rad as an extra cost option.

So I now conclude that the HD Rad became an extra cost option for the Tripower AFTER Feb 6.

Since the two March records have the Special Order 3.90 axles, I can't be certain that the 3.23 had finally become the standard release but since the HD Rad was now an extra cost option, I believe that the 3.23 was the standard release by then.

I haven't thoroughly checked my records from KC, Balt, and Fremont but it looks like the change to the 3.23 and the elimination of the HD Rad as a no cost option on Tripower '64 GTOs occurred after Feb 6 but prior to Mar 2 and appears to have been the case at each Plant on or about the same date.

I do have records of Tripower builds produced in March that show the 3.23 axle without the HD Rad.

I would welcome anybody that has a Tripower build that would further narrow the time line or contradict my new conclusion.

I can't explain why the revision to the 3.23 axle did not take place on Jan 27 as the SCN claimed and I do not know of any announcement that revised the effective date of the change. But the Manifest records make it certain that the Tripower builds continued to get the 3.55 axle as the standard release axle along with the no extra cost HD Rad for some period of time after Jan 27.