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All SX's used the TH400 3-spd automatic transmission, which was the mandatory M40 option for the Y-79 SX performance package. The only notable difference is the use of a 442-specification "OG"-code transmission with the W-32 engine option. This transmission produced firmer shifts than the standard "OD"-code TH400 transmission used on all other SX's.
The Y-79 SX option did not include a console shifter as part of the package, though one could order either the D-55 sports console shifter, or the W-26 Hurst Dual-Gate console shifter, with the SX package.
| 1970 | 1971 | ||
| Engine Option | L-31/ L-33 |
W-32 | L-32 |
| Transmission Code |
OD | OG | OD |
The 1970 SX used an "O"-type 8.5" rear differential with a 12-bolt cover. This is not the same as, and parts are not interchangeable with, the better-known "C"-type 12-bolt rear differential. The standard-equipment final-drive ratio differed, depending on the engine that the SX was equipped with: the L-33/L-31 equipped cars came with a 2.56:1 ratio standard, while the W-32 equipped cars came with a 3.08:1 ratio standard. The G80 Anti-Spin differential was not a part of the Y-79 or W-32 option, but was a mandatory option with the G92 3.42:1 axle ratio available on the W-32 equipped SX's.
The factory 1970 W-machines brochure, which includes the announcement of the availability of the W-32 option on the Cutlass Supreme lineup, also announces that the W-27 aluminum-housing rear differential was available on the W-30, W-31 and W-32 equipped cars. Olds also issued a memo early in the 1970 model year listing the availability of this option on the W-32 equipped SX.. All W-27 axles were equipped with an Anti-Spin differential.
In 1971 and following years, Oldsmobile turned to the use of the 8.5" "C"-type rear 10-bolt rear differential. With the loss of the W-32 option, the 2.56:1 ratio became the standard axle ratio for all SX's, and a 3.08:1 ratio was as low as one could go in gear ratios. There was a "W27-style" aluminum cover available over the parts counter for the "C"-type 10-bolt rear axle, but this was not a true aluminum center-housing axle as with the 1970 W-27 axle.
