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DWC
10-10-2017, 05:54 AM
The 68 Camaro I recently bought has a Muncie that the seller said was an M21.
After looking at the casting numbers, I believe it may be an M22. The casting numbers are 3857584GM, P8S06, 3925660, 3088336. From what I've read, it's a close ratio M22. Can anyone confirm this?

Thanks,

Daniel
232_ray
10-10-2017, 09:22 AM
It's possible that it's an M22 but it can also be an M20. Only way to really be certain is in the cut of the gears. The angle that the gears are cut is the for sure way to tell. Can u post pics? What about the input shaft is it a fine spline of course (26 tooth/ 10 tooth)?? Does the input shaft have grooves/rings cut into it? If so how many? Those casting numbers are good to ID the case mostly since munchies have been around so long people have changed them around soo much hard to ID them from the cases anymore.
MCB Matt
10-10-2017, 10:07 AM
DWC, you had sent me a PM with a quote request but I am unable to reply because you have that function turned off in your User CP.

You can email me direct: [email protected] or fix the permissions and you can receive PM's.

Sorry to jack this thread..

Thanks,
Matt
DWC
11-20-2017, 07:43 PM
I wanted to follow up to this thread. I got the engine and trans pulled this weekend. It seems I have a 10 spline, 1 groove input shaft.

Not sure if we can ID it with that info or I need to crack the trans open to look at the gears.

Daniel
andrewb70
11-25-2017, 03:25 PM
I wanted to follow up to this thread. I got the engine and trans pulled this weekend. It seems I have a 10 spline, 1 groove input shaft.

Not sure if we can ID it with that info or I need to crack the trans open to look at the gears.

Daniel

I believe that all M22s were 26 spline. So that is either a M20 or M21. You can probably figure it out by turning the input shaft while the transmission is in first gear and see how many turns it take to get one turn of the output shaft.

The M21 had a 2.20 1st gear and the M20 had a 2.48 1st gear. So a little over two turns is it a M21...closer to 2.5 turns, then it is a M20...

Andrew
232_ray
11-26-2017, 02:28 AM
Single groove on the input makes it an M21. 2 grooves is M20.
DWC
11-26-2017, 04:35 PM
Great info guys. It takes about 2.2 revolutions of the input shaft to get 1 revolution at the output shaft.

So, it seems I have a close ratio M21.

Thanks again,

Daniel
HIFLYR
12-02-2017, 05:33 PM
This guy be the man for Muncie 4sps a link to his web site is also on the page.
https://www.youtube.com/channel/UCxP2351joupD-Re3KFpDTNQ