The synchromesh transmission also has gears in constant mesh. However, gears can be selected without clashing or grinding by synchronizing the speeds of the mating part before they engage.

The sliding gear transmission is generally used in farm and industrial machines; therefore, we will only look closely at the constant mesh and synchromesh transmissions.

Constant Mesh Transmission

To eliminate the noise developed by the spur-tooth gears used in the sliding gear transmission, automotive manufacturers developed the constant mesh trans- mission, also known as the collar shift transmission (fig. 4-18). The constant mesh transmission has parallel shafts with gears in constant mesh. In neutral,

Figure 4-18. - Constant mesh transmission assembly.