Octania

"Hydra-Matic" embossed in the pan, I hear
the tag code obviously
VIN stamp

any internal differences to make note of?

Friend is seeking a genuine 1968 TH400 for his genuuine 1968 442. I have an OH core... it turns out to NOT be for a Hurst... Just a turnpike cruiser I guess. I assume it is like the OG type but with economy calibrated governor, etc.

Experts' input appreciated.

BlackGold

The tailshaft housing will have a date code cast in it, if you want to get ****. year and month. At least they did by the 1970 model year.

Octania

well, you know, I like to get **** as much as the next guy, but not sure where to look for this date thing on a tranny. Maybe where the shaft protrudes from the hole. Surely someone has a photo?

Oh my goodness why does everything garage related have to sound so naughty?

Rcktman442

It may be your lucky day, I have a TH 400 that I pulled from my real 1968 442 in favor of an OD trans, it was rebuilt as part of my original build and still has the OG tag. It has unfortunately been sitting for a while (13 years or so) but it has been stored inside, full of fluid and at the very least will need to be cleaned up and gone through just to be sure but it is what you are looking for and it worked great until it was replaced. I have no idea on a price but "make me an offer I cannot refuse!" LOL

Octania

The man needing it is in Lansing MI
Would prefer to do a pickup, not shipping

location of trans?

Rcktman442

Well that might be a long drive, i am in Enumclaw, WA which is just SE of Seattle.

BlackGold

Just a hunch, but I bet it'll be easier to find a '68 TH400 in the Lansing area than to drive to Washington .....
Even today, it's amazing how many Oldsmobiles you see parked in driveways in Lansing.

Chris, The casting number and date code for the TH400 tailshaft housing is on its right-hand side, upside-down. If in '68 they did it like my 1970 TH400 built in '69, look for a wagon wheel. In the center of the wheel you'll see the year it was cast, 69 in my case. You'll also see one or more dots punched between some of the spokes of the wagon wheel, designating how many months of the year has passed, 10 in my case for October.

I'll let you make your own 69 jokes.

Octania

this is like Jeopardy
One of us knows ANY question/ answer
Thanks!

joe_padavano

OK, this isn't directly related to Chris' questions, but why do GM date codes always sound like a puzzle from the movie National Treasure? Geeze, would it have killed them to just stamp "OCT 1969" or something equally easy to understand?

BlackGold

I think you're on to something. The wagon wheel which I described is actually a code for pizza. The dots were used to communicate pepperoni vs. sausage. What we think is a date code is actually one line worker telling the next what he's ordering for dinner.

Lots of GM parts used the dots-in-a-wagon-wheel method for a date code. Sometimes the dots only designated the month; there might be one or many dots in each slice of the pie. Other times each dot designated a week. So during the first week of October there would be one dot in the tenth slice of pie; during the next week, two dots; etc.

Since the "69" only had to be changed out once per year, using a center punch to make dots was certainly a lot simpler than keeping a complete set of letters and expecting the line workers to know how to spell.

But then there's the aluminum intake manifolds for the W-cars. A nice, simple, MM-DD-YY date code -- and then they go and hide it where no one can see it without removing the manifold from the engine.

Octania

My favorite: the Julian Day!
Easy enough to figure out... but for say C heads, used '67-69 model years and therefore cast '66 thru '69.... the year is only guesswork. Meaning, it does not matter, evidently.