Steel tag part # 3857573 on '65 Muncies

[Wayne M.]

A couple of days ago, Jim R. asked about the tag stamped (debossed ?) with 3857579 bolted to the sidecover of his L76. As usual John H. correctly responded that it was the Chev part # for the complete transmission assembly. This info is not (yet) flight judged; not sure about the higher (as in "on a lift") judging categories.

(link) https://www.forums.ncrs.org/showthre...73561&uid=6640

Carrying this topic a little further, (IMHO) this number means that Jim has either a 3.70 or 4.11 differential factory installed in his L76. The close ratio tranny gearset was obligatory with L79, L76, L78 and L84 in the 1965 model year.

Here's the question: Why does the '65 AIM (UPC M20/22, Sheet 1, Item 1) show 3857579 as being for UPC M20 with L79 only ? And why does the same sheet show 3857573 as being for L76 / L84 ? The power train charts all show the "general purpose" ie. standard axle ratio for these 3 engines as being 3.70.

AFAIK, there's nothing internally different in a trans with L79, compared to L76 or L84 (or even L78 with a 3.70 or 4.11 ratio), ie. they all have the same steel speedo drive gear on the mainshaft tail to accept the green 22 tooth or yellow 24 tooth plastic speedo driven gears, and, based on cars I've owned, would all have tag 3857579 with the 3.70 or 4.11 rear gears.

Has anyone ever had or seen an original tag 3857573 ? (no repops please, as LIC and CC reproduce this number for those that believe they need it to confirm L76 / L84, irregardless of rear end ratio, based on mention in the AIM). On eBay you can get any # your heart desires.

Well, enough for now -- there's a whole chapter for the two other axle groups (3.08, 3.36 and 3.55) and 4.56. And then there's the three M22 possibilities.....

[Jack H.]

Re: Steel tag part # 3857573 on '65 Muncies

Since there wasn't a physical distinction between M20 and M21 (close vs. wide ratio), my hunch is the different PN's are what makes the distinction...

[Jody B.]

Re: Steel tag part # 3857573 on '65 Muncies

Here's a picture of the transmission tag on my 1965-396 coupe that has a 3.70 rear and the original drive train.

[Wayne M.]

Re: Steel tag part # 3857573 on '65 Muncies

Here's a picture of the transmission tag on my 1965-396 coupe that has a 3.70 rear and the original drive train.

EXCELLENT STUFF, Jody. Precisely my point. (hey, my 396 has same rear FA 7_15_65 , but tag and orig. trans long gone).

Now the AIM and the re-pop catalogs show # 3857581 for L78 (396), which is CORRECT, but only for the "general purpose" standard 3.36 (or 3.08 or 3.55) axle gears, per the powertrain chart.