'65-70 4-sp Extensions (Tail Housings) cast # size

[Wayne M.]

Is there any significance to the part number character size on the tail housing (3857584GM). Out of 5 examples I have, 4 are the large (shown in bottom of pic) and one has the small font, with the space between the # and 'GM'.

I'm thinking that the small font is later production, or even service, but have nothing to back it up, other than a couple of known originals ['65-66] have the large.

Any thoughts appreciated.

PS: check out the bolt markings on the speedo bullet retainer; B&H on one; anchor head on the other.

[Joe L.]

Re: '65-70 4-sp Extensions (Tail Housings) cast # size

Is there any significance to the part number character size on the tail housing (3857584GM). Out of 5 examples I have, 4 are the large (shown in bottom of pic) and one has the small font, with the space between the # and 'GM'.

I'm thinking that the small font is later production, or even service, but have nothing to back it up, other than a couple of known originals ['65-66] have the large.

Any thoughts appreciated.

PS: check out the bolt markings on the speedo bullet retainer; B&H on one; anchor head on the other.

Wayne-----

As you know, the GM casting #3857584 extension housings were used from 1965 to 1970. During this period, they were widely used across all GM car lines using the Muncie transmission. This included most Chevrolet models, Pontiacs, Buicks, and Oldsmobiles. So, wherever these things were being cast (likely at Bedford, IN if they were all manufactured internally by GM) they were making a LOT of them. This piece is a permanent mold casting so there were undoubtedly many molds. I expect the difference in the configurations of the casting numbers may have been a feature of different molds. Of course, molds using one or the other font styles may have predominated during certain periods of time.

In any event, attached find a photo of the extension housing of the known-original from my late 1969. You will note that it has the large font style as well as an "anchor" head-marked speedometer fitting retainer bolt.

I can also tell you that later SERVICE examples of the 3857584 that I have and have seen all have font style IDENTICAL to that on my 1969 as seen below.

[Wayne M.]

Re: '65-70 4-sp Extensions (Tail Housings) cast # size

... So, wherever these things were being cast (likely at Bedford, IN if they were all manufactured internally by GM) they were making a LOT of them... .

Thanks, Joe -- your original owner late '69 answers a lot on my original query.

I see that Bedford IN is about 140 miles from Muncie (see pic of remaining smokestack that I took in April 2007 -- plant probably now completely demolished). Would the other aluminum components also have been cast in Bedford [main case, side cover] ?

From a previous thread, it was explained to me that Muncie was operated by Chevrolet, with shipments to Chev and BOP assembly plants, as required.

What about the gears and mainshaft ? Were these fabricated elsewhere, relegating Muncie to merely an assembly facility ? I notice that those comtemporary service items were labeled 'United Delco'.

[Joe L.]

Re: '65-70 4-sp Extensions (Tail Housings) cast # size

Thanks, Joe -- your original owner late '69 answers a lot on my original query.

I see that Bedford IN is about 140 miles from Muncie (see pic of remaining smokestack that I took in April 2007 -- plant probably now completely demolished). Would the other aluminum components also have been cast in Bedford [main case, side cover] ?

From a previous thread, it was explained to me that Muncie was operated by Chevrolet, with shipments to Chev and BOP assembly plants, as required.

What about the gears and mainshaft ? Were these fabricated elsewhere, relegating Muncie to merely an assembly facility ? I notice that those comtemporary service items were labeled 'United Delco'.

Wayne-----


The GM Bedford, IN foundry is permanent mold/die casting aluminum foundry. So, I think that the Muncie extension housings, side covers, and rear bearing retainer plate could have been manufactured there. It would have been the only GM foundry of the day with aluminum permanent mold/die casting capabilities. So, if these parts were not manufactured at Bedford, then they would have to have been cast at a supplier foundry. I have seen the "CFB" casting marks on some of these pieces and that would confirm their Bedford origin. Most don't seem to have any casting mark identifying an origin. However, that would tend to reinforce the Bedford origin inasmuch as GM usually always required outside suppliers to identify pieces with a casting mark.

The Muncie main case was an aluminum sand casting. I don't know where these were made. However, it may also have been Bedford. I don't know if Bedford ever did any sand casting since they were primarily a permanent mold/die casting foundry, but it's possible they did some sand casting. Otherwise, the only other GM aluminum foundry of the day was Massena, NY. I believe Massena did do sand castings at that time.

As far as I know, the gears, mainshaft, and most other internal parts were fabricated/machined at Muncie WHILE THE MUNCIE WAS IN PRODUCTION (i.e. until 1974). The machining of the cast aluminum parts was also done at Muncie. Sometime after 1974, I believe that manufacture of SERVICE pieces was transferred elsewhere.

For many years, most GM SERVICE transmission parts were packaged and sold under the United Delco brand. These were supplied through both the GM parts system and the Delco parts system, although not all parts were available through Delco. Nevertheless, all were branded United Delco.