The Borg-Warner 35 transmission (BW-35) is an automatic transmission produced by the BorgWarner company. This article also applies to variations—the M-36 and M-37. When this article refers to "M-3x" it refers to all models. When model number specific it will use the exact model number. The "3" in the number refers to the specific series of transmission. The M-3x, 4x, 5x and 6x transmissions are all aluminum cased transmissions that are related to the M-35 (the first of the aluminum Borg-Warner automatics). In this case the rising series number is relative to transmission strength—a larger number will withstand more power than a smaller number. This isn't, however, a general rule with Borg-Warner automatics. The earlier M-8 and M-1x cast iron case transmissions are much stronger than the aluminum models, although the M-6x may handle as much power as the M-1x series. The second number refers to a specific variation. This usually indicates a higher torque load capability, but may refer to other variations that may not increase torque rating. The M-3x has three forward and one reverse gears. The selector lever varies depending on years and car models the transmission is used in. All models follow a quadrant which has six stations. Early models have two drive positions marked with a "2" and a "1" (P-R-N-D2-D1-L; Park, Reverse, Neutral, D2, D1 and Lock). These models start off in Second gear when in the D2 position. This is useful for economy in relatively flat terrain and for starting on slippery surfaces (wet mud, snow, ice, etc.). When placed in the D1 position the transmission shifts through all three forward gears. In "Lock" the transmission can be locked to prevent upward gear changes and will provide maximum engine braking in 1st gear and moderate engine braking in 2nd gear. By selecting L from stationary, or before an upward gear change into 2nd gear, the transmission will become locked in 1st gear. By selecting L from D2 or D1 while in 2nd gear, the transmission will become locked in 2nd gear or from D2 or D1 when cruising below 55 m.p.h (88 k.p.h.) will effect an immediate downward change and lock in 2nd gear. In both these instances, the transmission will automatically change down into 1st gear when the car speed drops below 5 m.p.h. (8 k.p.h.). Should 1st gear be required earlier, reduce the car speed to below 30 m.p.h. (48 k.p.h.)