Interesting stuff guys.
Couple thoughts. Rocky, why would the trans affect emissions? I thought the cam was changed for that reason, didn't realize the trans had an impact. The higher gear multiplication provided by the M20 reduction gears was better for emissions? Seems a bit counter-intuitive to me.
The Excerpt with the Fig. 3 was interesting. I knew the trans changed with the mid March EGR snafu.
So no surprise that the Chart gives the old and new trans p/ns and codes.
I thought I was on to something when I saw the new p/n 6271518 code WK was tagged as a Close Ratio.
But neither of the two "Old" Muncie 4 spds was tagged as a Close Ratio.
But when I checked p/n 332578, code FC, I found it listed in the '77 MPC and described as Close Ratio. So just another error in the documentation.
Curiously, the 6271516 and 6271518 were not listed in that '77 MPC.
But I found a forum post elsewhere that indicated the 6271516 and 6271518 were used in the '72-'74 Corvette (at least until the Muncie was discontinued and the B-W T10 superseded it). In '72, the Corvette also made use of the 6271517 which was the M22 version. Same Manifest codes as used in the late '73 TA too. So looks like at mid year, PMD was able to make use of the same Muncie 4 spds that the Corvette was employing.
So now that I know my TA would have been built with the Code FC M21 (mine was built in January), I'm only a little torn as I think I might prefer the gearing of the M20 that I have acquired anyway.
I'm pretty certain the rear axle housing is original (center casting has a Jan '73 cast date) but I'm not sure it still has the original gears in it. I'll need to check on that.
Thanks for all the info on this. I love this kind of detail even though I am not planning a very correct resto for this TA. I still like knowing what it was born with.
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