4K gearbox

What type of gears are used for forward and reverse in a manual gearbox? Give an explanantion for your choice.
In a manual gearbox, there are two main types of gears used to transmit power, from the input shaft from the engine to the output shaft to the diff or axle. Forward gears e.g 1st, 2nd, 3rd, 4th, 5th; use helical or constant mesh gears as there is more contact surface available and they are alot quieter than straight cut gears. Reverse gear, however uses spur or straight cut gears as the gears can slot easier into place, but, are not as strong as helical cut gears. The reverse driver, driven and the reverse idler are all straight cut gear.

What is the purpose of a bualk (synchro) ring.
A baulk ring is a gold coloured, dog toothed ring that is pushed against a free spinning gear to speed up or slow down the corresponding gear before it is engaged. For example, when driving in 3rd gear, and want to change to 4th, the baulk ring will engage and speed up the 4th gear, so when the change is made, it is done smoothly as opposed to being forced into gear, which can cause real damage.

What is the purpose of a synchromesh unit? Explain the operation of a synchromesh unit.
A synchromesh unit includes the hub, slider, bearings and baulk ring. When changing gears, this unit slides either left or right depending on the gear needed. The selector fork pushes or pulls the slider, to allow the baulk ring to match the speed of the gears. When the gears are moving at the same speed, the slider will engage the corresponding gear while being limited by the synchro hub and detent system.


What type of bearings do we find in gearboxes?
Different gearboxes use different bearings, but the most common types found in a car gearbox include roller needle, caged roller and main shaft bearings. The reason gearboxes have different types of bearings is because of the amount of load each component goes through when in use. 

Give an explanation of a gear ratio.
In a gearbox, each gear has a corresponding gear of a different size. When a gear is selected e.g 4th, the ratio would be 1:1 as the gears are the same size and turning the same speed. Where as with other gears, one gear will be smaller and turn alot faster than the bigger corresponding gear.  The different gear ratio's allow different speeds to be achieved as you change through the gears.