Trans Dates Research help requested by DaveP

[DaveP]

I haven't done a project like this for awhile. Let's try another one. For you guys that have 4L60/700R4's on the floor, or out of the truck, I could use some help developing enough data points to draw a conclusion:

There are two Dates on a trans. The assembly date (Assy date), and what I believe to be a date the case was machined. Ie, (Machined Date). I'm trying to establish what "year" is denoted in the Machine Date.

Here's the Assy Date: Model Year, Trans model (LHM), Julian day built (001-365), and shift (A,B,C)

Here's the Machined Date: Located on Driver's side, rear park-pawl boss: Julian Day and last digit of year.

What I'm interested in is this: Model Year is always just that. A 1992 M/Y LHM could be installed in a Ty built on October 15, 1991. So the Assy date should be 2LHM240 to 2LHM270. Those are the days in September, the preceeding month. But the case was machined in 1991. Is the machine date year,(last digit) the Model year, or the Calendar year?

I'm interested in all subject trans cases that are MD8 on the right front of bell housing.Particularly Julian days between 260-365. Please post the complete Assembly Date, and the center set of 4 digits of the Machine Date from any cases you may have. They do not have to be SyTy LHM's for this survey. Here's the MD8:

Thanks,
DaveP

 

[SY-1193]

Re: Trans Dates Research help requested by DaveP

1lhm067b
21 681 0777 << this stamping doesn't look like yours...mine 2 digits then 3 then 4 yours was 4 and 4 ???

From my '91 SY. Not the days you are looking for.

 

[DaveP]

Re: Trans Dates Research help requested by DaveP

1lhm067b
21 681 0777

From my '91 SY. Not the days you are looking for.

That's OK. I appreciate it. Because you posted the entire set of Machine Date, we can learn something else:

The set of numbers on the Park Pawl boss is comprised of three sets. The middle is the machine Date (Julian).

The first set "21" could be 'codes' for selective components based on raw measurements from the machined case. I'm thinking the servo pin length, and the Lo-Reverse piston pressure plate thickness. The cases I've inspected have all been 1,2,3 in this position.

The third set, "0777" is always 4 digits, but is a value that's all over the place. I have no clue what the third set is.

 

[SY-1193]

Re: Trans Dates Research help requested by DaveP

I also have this document that is the build date log of the truck if that helps. (I have just about every scrap of info/papers cards that came with my truck). Off of the subject of your post but maybe something you would be interested in/ maybe it ties in with the trans dates somehow?.

 

[turbodig]

Re: Trans Dates Research help requested by DaveP

Crappy picture... but this is an MD8, 3LHM. It replaced my factory trans, GM dealer replacement.

The numbers are:

33 23 8 0830

 

[DaveP]

Re: Trans Dates Research help requested by DaveP

Thanks for the reply, Dig. Interesting example. You indicate this is a replacement transmission. I've seen numerous GM replacement LHM's, and they have been the same silver paint, but the model has been stenciled on the case in black paint. This one is the first I've seen with the little data plate.

Here's what I get from the numbers:

The Machine Date 238. Probably January 23, 1988. (There were no 700s produced in 1998). An early K-case 700 has two 1/4MPT pressure ports on the passenger side, that are gone by the 1990 model year. If your case has these two extra pressure ports, it's a 1988 Case.

The Julian date on the tag is 1027. The 102nd day of 1997. Which is April 12th. Did this trans get installed after Mid April, 1997? If so, I got the correct date off the tag. The "2520"can also be made into a Julian date, but in the years 90,92,00, or 02. None of which I think "fit". 2520 is probably a job or sequence number.

Thanks for posting. Please let me know if my conclusions "fit".
DaveP

 

[phoonTy]

Re: Trans Dates Research help requested by DaveP

Great post Dave. This is going to be some great content for the Tech section and Historical Vault. And, if it's okay with you, when we get some conclusive findings, I'd like to make it a feature post at www.SyTySoGT.com.

 

[DaveP]

Re: Trans Dates Research help requested by DaveP

I'll add a few from what I have installed and laying around the shop and yard:

8TZM088B
32--828-2530

1988 case, March 28 1988 build and machine date, MD8, K-case, extra pressure ports on pass side. Original Usage unknown.


5MSD111A
33-1115-0712

Machined and Assembeled April 21, 1995.
This is a 1995 Astro Van 2WD. M30. K-case, extra bosses for external P/N switch on drivers side.

2TBM097C
22-942-3075

1992 April 07 assembly, April 04 machine. MD8, K-case, 1992 2WD Blazer trans.


3TBD356A
42-3522-2477
M30, K-Case, has ink stamp "356A" below machine date. Known 1993 Blazer 2WD.

Finally a Julian Assembly date at the end of the year. Dec 21, 1992 Assembly, (Model Year is "3") and a 352, December 17 1992 Machine date. (They used the calender year, NOT the Model year). This is what I'm looking for: A model year that was assembled the previous calendar year with a calendar year machine year.

I have a couple more that are installed. I'll add them as I get them on the lift. One 3TBA and one 1LHM.

 

[dgoodhue]

Re: Trans Dates Research help requested by DaveP

I have 2 Sy trans out. I will be swapping out the 92 Ty trans sometime this summer (hopefully June)

The number for Sy 2661 is

1lhm130c
21 1281 1525

Sy1754
1lhm087b
11 0871 1128

 

[turbodig]

Re: Trans Dates Research help requested by DaveP

Thanks for the reply, Dig. Interesting example. You indicate this is a replacement transmission. I've seen numerous GM replacement LHM's, and they have been the same silver paint, but the model has been stenciled on the case in black paint. This one is the first I've seen with the little data plate.

Here's what I get from the numbers:

The Machine Date 238. Probably January 23, 1988. (There were no 700s produced in 1998). An early K-case 700 has two 1/4MPT pressure ports on the passenger side, that are gone by the 1990 model year. If your case has these two extra pressure ports, it's a 1988 Case.

The Julian date on the tag is 1027. The 102nd day of 1997. Which is April 12th. Did this trans get installed after Mid April, 1997? If so, I got the correct date off the tag. The "2520"can also be made into a Julian date, but in the years 90,92,00, or 02. None of which I think "fit". 2520 is probably a job or sequence number.

Thanks for posting. Please let me know if my conclusions "fit".
DaveP

Affirmative on the ports. I really wondered about this... it didn't fit a 3LHM trans, since the ports went away in 91. The trans that's in it now is supposedly 92 ty... no ports.

I'm 98% sure my factory original case had the ports. Mine was an early sy (689, before the 91.5 split), so this is also plausible.

I'm fuzzy on the exact year of the replacement, but my memory says '96. It may have been early '97. I'll look back and see if I can find paperwork. It's plausible, though.

The paint is my doing... I did a mismash of aluminum paints.

I just got a bore/snake camera the other day... I'll poke it under the truck and get a snap of the trans that's in it.