[RJBaileyrn]

Hi guys,
I have a muncie 4-speed in my 69 Camaro. It has a tag with the partial VIN that seems to match up correctly, but when I count the teeth, splines, and all, it doesn't add up correctly.

I have:
26 spline input shaft 1 1/8", no rings/grooves
27 spline output shaft
21 tooth Input gear
25-22-19-17 cluster gear tooth count

Per the following website: http://www.nastyz28.com/chevy-manual...tification.php

I believe it is a 66-70 M-20 2.52:1 box that has had the input shaft replaced from the original 10 spline shaft, thus likely making it the original tranny.

Anyone concur or have other likely suggestions?
Thanks in advance. RJ

[bcm66]

What is casting number of main case? 3885010 is 66-67, 3925660 is 68-69 and sometimes into early 70.

Tag will not have a partial VIN on it. That is an application code. What are the numbers on that tag?

What is information stamped on main case? That is usually on back edge of main case. STAMPED letters about 1/4 inch in height. There will be an assembly date and a partial VIN in most cases.

Cluster gear tooth count verfies M20, and like you said, input shaft may have been changed. Output shaft goes with year being 66-70.

But main case and data on tag will tell you the most about narrowing down the year.

[RJBaileyrn]

Stamped at back edge- P9P16
Tailshaft case casting #3857534
main case says 3088336

[RJBaileyrn]

Main case #3925660
side cover #3950306

Can't find the tag right now

[bcm66]

Main case, side cover and assembly date of September 16, 1968 point to this being from a 69 vehicle. How does the assembly date compare to the assembly date of the body of your car? Partial VIN on transmission would be only way to confirm this is original to the car, even if dates are close.