Jermo

Can any read the attached codes and tell me what this transmission is? I do know it’s a m22

Mr D.

How do you know it's a M22?

3925661 is a 1969 - 1974 Muncie Transmission Main Case.

https://www.chevydiy.com/muncie-4-sp...ication-guide/

Jermo

When I had the clutch replaced the installer said it was a M22

Mdbirk

The last Muncie case was the 3925661, the casting was used the last quarter of 1969 for 70-74. The “661” is considered the strongest factory GM case. It's very similar to the 660 case, It was used primarily with the 26-spline and larger 32-spline output-shaft , they were beefing things up since the 454 engine was introduced for 70, although there seems to be a overlap from 1969 to 1970, with both of these cases.
But cases are often swapped rather than being repaired, the best way to determine if you have an M20, M21, or M22 is to simply look at the gears. Without removing the sidecover you can look at the input shaft and check for identification grooves cut into the spline, your cars a 71 lt1 of which 1949 were made and in 71 they only made 130 Corvettes with m22s.

62corvette

Did you ask him what he saw that caused him to say that? Over the years, I’ve probably seen 50 supposedly M22’s that weren’t.

Rescue Rogers

you can not tell a M22 RELIABLY from the outside. Unless he pulled the side cover and inspected the gears you cant tell. THe cut lines on the input shaft arent reliable for a M22 any longer. What does it sound liike when you drive it?

https://www.jalopyjournal.com/forum/...cation.375443/

Jermo

It has a high whining noise while driving

Rescue Rogers

well, thats a good reason to believe its a M22, next time its out just pop off the side cover and take a pic of the gears. Ive rebuilt and changed gears and gear ratios inside the cases before so the case numbers dont tell the story of whats currently inside them....but they will tell you about the cluster shaft size which is the important part by the build date

Rescue Rogers

https://www.chevydiy.com/muncie-4-sp...tion%20process.

68-74 case with a 1 inch cluster shaft bore...

Nowhere Man

After the assembly date stamp there will be either a letter A B or C. Which letter is stamped on it

Rescue Rogers

there MIGHT be a stamp....

dennis

Jermo

this is all I could get a photo on while still in the car

Rowdy Rat

The CC1 code indicates a service transmission built in 1971.

What year car do you have?

Regards,

Stan Falenski

Jermo

1971 LT-1 Convertible

Rowdy Rat

The CC# stamped transmissions with the five digit number accompanying it on the transmission case are typically warranty replacement transmissions.

Odds are, something happened to your car's transmission while it was still under warranty and GM replaced it. Absent any additional information, that would be my guess.

Regards,

Stan Falenski