T90A1 Casting Codes

radtech · Post by **radtech** » Fri Mar 16, 2018 10:30 pm

I have a T90A1 transmission originally out of a 55 CJ5 with 7-5 cast where the date is cast on my M38.Anyone know what this code is?And another marked 5-21.

I split your unrelated post from the lift shackle post so it will be more noticeable here on it's own merits and more likely draw a few answers for you.
Wes K

dpcd67 · Post by **dpcd67** » Sat Mar 17, 2018 6:36 pm

The T90 out of my M38 is also cast in, 5-21. I have no idea what that means but it was paired with an RMC engine in the 58K range. Must be a spare transmission from the supply system.

Post by **wesk** » Sun Mar 18, 2018 1:13 am

I will guess it is only month & day. The year must be indicated elsewhere on these later trannies.

Then there are these earlier units with the full date code.

4x4M38 · Post by **4x4M38** » Sun Mar 18, 2018 5:13 am

I have seen a decode somewhere on the Internet but am
having no luck in scraping it up.

radtech · Post by **radtech** » Sun Mar 18, 2018 10:01 am

Studebaker,Checker and GM also used the T90A1.It may be a manufacture code.

dpcd67 · Post by **dpcd67** » Sun Mar 18, 2018 2:33 pm

On the top machined surface of mine it has stamped L5 2-3. Isn't that usually the assembly date? 1955?
And cast in, 5-21 on the side.

kenperkins · Post by **kenperkins** » Sun Mar 18, 2018 6:52 pm

the side casting on mine appears to be 7-57 and is cast upside down to the top of case ( I saw other examples of this while surfing Google).
The stamping in the machined surface is H197-2 so, if H=8 and 19 is the day, 7=1957...but cant find any info about the - 2. Looks like case was cast in july and built in aug.

Mike_B · Post by **Mike_B** » Sun Mar 18, 2018 9:14 pm

I'm guessing the -2 could be second shift...

Mike B

radtech · Post by **radtech** » Sun Mar 18, 2018 9:16 pm

There are many theories though most don't fit but no one knows exactly what the numbers mean.

kenperkins · Post by **kenperkins** » Sun Mar 18, 2018 9:33 pm

one site I found, see casting #s

http://www.crankshaftcoalition.com/wiki ... ation#T-90

dpcd67 · Post by **dpcd67** » Mon Mar 19, 2018 11:28 am

Ok, according to that rule, my T90 (L5 2-3), was made in December 5th, 1952. Or 1953; they weren't sure so stamped both. Or the 3 is the shift?
Clear now; no one on earth knows.

Post by **wesk** » Mon Mar 19, 2018 11:34 am

It's only an issue on the 54 or so and newer T90's. The earlier have the old fashion plain jane 3 set of numbers dates.

I doubt very seriously that there is one cast date code that fits all brands.

The most common casting screwup on the M38 was the test run of the new 804380 blocks in Jan 1952. Although the block blueprint at Willys was already changed from 641087 to 804380 the news never made it to the foundry and the test run blocks all had 641087 cast on them.

This block was suppose to be an 804380 block!

dpcd67 · Post by **dpcd67** » Mon Mar 19, 2018 12:40 pm

It is an issue for me, as I have a 51 jeep with a replacement transmission for which i want to know the manufacture date.

Post by **wesk** » Mon Mar 19, 2018 1:03 pm

If you have a tranny in your 51 M38 that does not have a date code like this then you have a later incorrect tranny.

You will need to find a correct dated tranny the one you have is much newer than 1951.

Here's a 1952 unit from a 52 M38A1

4x4M38 · Post by **4x4M38** » Mon Mar 19, 2018 1:08 pm

Or he has a motor pool jeep...