Overview
Casting numbers are an important starting point for Muncie identification, but they are not a stand-alone proof of model. Use them with serial/date codes and case feature checks.
Common Casting Number Examples
| Casting Number | Likely Association | Approx. Years | Notes |
|---|---|---|---|
| 3925660 | Often associated with M22 | 1969-1974 | Commonly cited; verify codes and internals |
| 3925661 | Often associated with M20 | 1966-1970 | May appear in mixed listings; verify details |
| 3925664 | Often associated with M21 | 1969-1974 | Use with date/serial confirmation |
| 3885010 | Early Muncie usage | 1965-1967 | Check exact application and stamping consistency |
How to Read a Casting Number
Clean the case carefully and photograph the number in good light. Dirt, paint, and wear often cause digit misreads that lead to incorrect model claims.
Normalize the number by removing spaces and punctuation before comparing it against a decoder list.
Limits of Casting Data
- Casting numbers can overlap across variants or years.
- Cases and components may be mixed during rebuilds.
- A correct casting number does not prove matching numbers status.
Best Practice
Use the casting number decoder first, then confirm serial/date code alignment and physical traits. Finish with a road-test noise/behavior check when possible.
Frequently Asked Questions
Can a casting number confirm an M22 by itself?
No. It is a strong clue in some cases, but authenticity requires additional verification.
What is the next step after decoding a casting number?
Check serial and date codes, inspect case features, and compare with model-specific identification guides.
Why do sellers list the same casting number for different models?
Some listings are mistaken, incomplete, or based on assumptions; always verify with multiple data points.
Next Steps
Use the Identification Tool to score your transmission, then run the Value Estimator and compare rebuild options on the Parts Comparison page.