A few Muncie case date questions

[Dennis H.]

I have been looking at Muncie Main Cases and paying particular attention to casting vs. Assy dates and have a couple of questions.

Example #1 – 3851325, has a 5 to the left of the status marker, status marker has 2 dots on top and J on bottom, date marker is blank. Assy date is P0914. My guess is this is a 1965 case that was built Sept 14 1965???

Example #2 – 3851325 has lines but no circle around them, no dots or numbers that you can make out. Maybe the letter I or J under what would a status marker line. This case has no VIN or Assy date stamp. Any idea on cast date based on the letter I or J?

Both cases have what looks like a larger letter I cast or scratched into the case on the right side in different locations. What is this?

Was it common to not have numbers and dots in the casting date circle?

[Joe L.]

Re: A few Muncie case date questions

Dennis-----

Yes, quite common. In fact, even in cases where there are characters or "dots" within the bi-sected circle, there is no YEAR information----just month, shift, pattern number, etc. This makes the information on the castings near useless for anything that's of import now.

A case with no VIN derivative usually means a transmission with a SERVICE origin. A case with no VIN derivative OR manufacturing code usually means a case with a SERVICE origin.

Muncie main cases were sand-cast aluminum. Except for intake manifolds and cylinder heads, aluminum sand castings were fairly unusual in Chevrolet cars of the 60's and 70's. The intake manifolds and cylinder heads of the period were all cast by an outside supplier, Winters Foundry of Canton, OH. However, Winters did not manufacture the Muncie main cases. I've never been able to confirm where they were cast. It may have been the GM aluminum foundry at Bedford, IN. However, I think that Bedford does mostly permanent mold-type castings. So, I'm still wondering about the Muncie main cases. Does anyone know? Any GM Powertrain-Bedford employees out there?

[Dennis H.]

Re: A few Muncie case date questions

Thanks Joe. I have been in search of a main cast to match up with a tail housing, this helps.

[William C.]

Re: A few Muncie case date questions

Just keep in mind there were detail changes to the boss for the top bolt on the 64 case as opposed to the '65, the '64 used a boss shaped like a fingertip while the later version used a rectangular shape (more "meat" for the threads)

[Wayne M.]

Several Possibilities

Too bad you don't have close-up pics; there are so many visual variables on these cases.

Your Example #1: The 5 is probably the mould #. What you refer to as status and date circle positions are the order found on (shifter lever) side covers. For main cases, I have always seen the date on the left and the status on the right. Don't know what the "J" could be, other than a badly cast numeral. The 3 dots would normally mean the 3rd week of the month. Latest 325's Ive seen are about P0815 (mid-August 1965), as big Chev EOP was up to 3rd week of August.

P0914 -- don't believe Muncie was assembling "325" transmissions as late as 14th Sept 1965; they would have been the "010"s for 1966 production. Where is the P0914 stamped ? If on the left side lower right corner of the shifter cover flange, then it's 14th Sept 1963 (ie. '64 production). But the letters Pat. Pending would be immediately under the "325" cast # in this time frame. If the P0914 is on the passenger side, is the edge of the maincase ground out in a crude circular spot prior to the stamp being applied ? If so, then the date refers to 14th Sept 1964 (early '65 MY production). This grinding procedure started at beginning of production for 1965 muncie transmissions (earliest I've seen is P0812; latest is about P0920) At that point they probably realized that they could get a good imprint on the raw casting, without grinding.

Another feature [as already mentioned]: the top rear bolt boss (maincase-to-tail) casting has a round forward shape (like the one at the bottom) up until about the first few days of December 1964 (assembly); after that, the boss is square at the front.

Your Example #2: Are these lines a single horizontal line with 5 vertical lines equally spaced intersecting ? This is representative of a "661" case [does it have a bottom drain plug ?]. Both the "660" ['68-69] and "661" case moulds ['70+] may have been used to replenish the service supply of "325" needs (ie. with the 3/4" dia. countershaft). In this instance, the "325" casting number is more faint than regular '64-5 production. Also, these service maincases have a wide(r) VIN and assembly date stamp pad surface, which is the first give-away on a "325" service casting. In your case, that may also explain the lack of P-number and VIN derivative. You'd have to email a pic of that I or J for me to even guess.

The casting circle (numbers especially) and dots are not always easy to read (casting flash), and sometimes do not jive with the "P" assy. date, probably due to inventory FILO, etc.

The crudely scratched "I" [letter or Roman numeral] is often seen, but this tends to vary with the mold #.

[Dennis H.]

Re: Several Possibilities

I have a 325 case with P0914 stamped in it along with some other chevy VIN stamped along the top of the case. It is my understanding the 325 case was only used through the 65 model year reguardless of what car it went in. If this is so than I'm guessing what I have is a 14 Sept 64 assy case.

I will post some pictures of what I have been looking at tomorrow. What started this whole thing was that we re-stamp blocks, why not a transmission main case.