This transmission is a basic carry-over from the '64 model year. Like the '63 Muncie close ratio, the original '65 input shaft should have one identification groove. 1964 and later Muncies used a first gear sleeve on the mainshaft for better lubrication. Early Muncie characteristics (1963-65) are as follows: 71/48-inch cluster gear pin, 51/416-inch coarse thread studs to attach shifting rods, speedometer gear on left side, thin blocking rings.
1965 Rear Axles
All '65 Corvette rear axles are stamped with an alpha-numeric identification code. The 7-digit code contains the axle code prefix, the month and day build code, an axle plant letter suffix code, and, on positraction axles, a letter code stamped below the axle code to provide source information. The plant code was first used in 1965.
On the '65 Corvette IRS rear suspension the differential code is stamped on the bottom of the differential carrier housing just forward of the rear end cover. The axle code reads from left to right. The two-letter prefix designates the gear ratio and any other specific information about the axle. The calendar month is designated by a two number code from January (01) through December (12).
From Corvette by the Numbers by Alan Colvin, used with permission of Robert Bentley Publishers.