Decoding my muncie
Thread Starter
Racer
Joined: Feb 2013
Posts: 477
Likes: 15
From: Long Beach Ca
Decoding my muncie
I'm trying to figure out if I have a close or wide ratio muncie. Ive been under the impression it was a close ratio but I just figured out I have a 355 rear gear ratio, (AN stamped on case). I was under the impression it was a 370 ratio. 
From what I've read, the M21 wasn't available with 355 gears in a 66 L79. The car was built in late April 66. Here's the numbers on the main case 6S120592 , (matches vin #) and 3885010. The side cover is 3884585. Thanks Mac
Pic is of the differential.
From what I've read, the M21 wasn't available with 355 gears in a 66 L79. The car was built in late April 66. Here's the numbers on the main case 6S120592 , (matches vin #) and 3885010. The side cover is 3884585. Thanks MacPic is of the differential.
Burning Brakes
Joined: May 2011
Posts: 1,138
Likes: 39
From: Florida
The case numbers match for a 66/67. Input should be 26 and 27 for the cluster for 21. Either pull the tranny, for input verification, as evindenced by one line or pull the side cover and count the teeth on the input/cluster. 21 input and 25 cluster are 20 or two lines on input. Hope this helps!!
Drifting
Joined: Dec 2006
Posts: 1,946
Likes: 407
From: Bronx New York
[QUOTE=SS409;1585012981]I'm trying to figure out if I have a close or wide ratio muncie. Ive been under the impression it was a close ratio but I just figured out I have a 355 rear gear ratio, (AN stamped on case). I was under the impression it was a 370 ratio. From what I've read, the M21 wasn't available with 355 gears in a 66 L79. The car was built in late April 66. Here's the numbers on the main case 6S120592 , (matches vin #) and 3885010. The side cover is 3884585. Thanks Mac
QUOTE]
What i've seen in Nolands book and the ncrs guide agrees with your conclusion in a small block. 3.55= L79 and M20.
From what I've read, the M21 wasn't available with 355 gears in a 66 L79. The car was built in late April 66. Here's the numbers on the main case 6S120592 , (matches vin #) and 3885010. The side cover is 3884585. Thanks MacQUOTE]
What i've seen in Nolands book and the ncrs guide agrees with your conclusion in a small block. 3.55= L79 and M20.
