The Manual Gear Box Mazda 323

The manual transaxle i disassembled (pulled apart) was from a Mazda 323. It consisted of these parts, a mainshaft that houses the gears, selector fork(interlock mechanism) that are used to prevent the engagement of more than one gear at a time, an input shaft that houses the driver gears and next to this on the mainshaft are gear selectors which are the driven gears, reverse shaft also known as reverse shift rod and reverse shift sleeve and another reverse shaft but smaller, all used together to select the reverse gear, and at the bottom of the gear box is the crown wheel which is known as the final drive inside the gear box.This is a step by step of how i did the task i was given.
1) Remove all 12 bolts holding on the transmission case.
2) Remove the bolts securing the reverse gear idler shaft.
3) Remove bolt securing the interlock sleeve.
4) Remove the case.
5) Remove the reverse idler shaft and gear.
6) Remove the bolt from the reverse gear shift rod sleeve.
7) Remove the roll pin, using a pair of pliers and also remove magnet if fitted.
8) Remove the aluminun plug from the side of the transmission housing,by levering the reverse lever shaft with a flat blade screwdriver from inner end this will push the plug out.
9) Remove the reverse shift rod.
10) Remove roll pin from crank lever shaft using a hammer and a dot punch.
11) Remove crank lever shaft and lever.
12) Remove gear selectors and gears as one assembly.
13) Remove seletor forks from gear assembly.
14) Remove final drive.eg crown wheel.
Once all in pieces i counted how many teeth were on each component such as
1st gear on input shaft has 12 teeth.(driver gears)
2nd gear on input shaft has 18 teeth.
3rd gear on input shaft has 31 teeth.
4th gear on input shaft has 37 teeth.
1st gear on mainshaft has 41 teeth.(driven gears)
2nd gear on mainshaft has 37 teeth.
3rd gear on mainshaft has 40 teeth.
4th gear on mainshaft has 34 teeth.
The pinion has 29 teeth and the crown wheel has 77.
Then i had to calculate the gear ratio. Definition= the number of turns of the input to produce 1 turn of the output.Its easy and il show you.
Ratio calculation:
Formula: the number of teeth on the driven gear divided by the number of teeth on the driving gear.
Lets say the driven gear is 44 and the driver gear is 11 the driving gear must rotate 4 time to rotate the driven gear once. This ratio is said to be 4 to 1.
The torque of the larger gear is 4 times that of the smaller gear.
So after i done that i put it all back together which is basically the reverse of the disassembly.
The purpose of a manual gearbox is: To allow drive to operate the engine in its most efficient speed range.To allow driver to select a suitable gear ratio to increase engine torque(torque multiplication) to match an increased load requirement.Change down to a lower gear, a higher numerical gear ratio. Allows driver to select a suitable gear to reduce engine torque multiplication, in favor of increasing vehicle speed, as load reduces.(change up to a higher gear- a lower numerical gear ratio. Allows driver to select neutral and disconnect drive. Allows driver to select reverse gear and drive vehicle backwards.
Note:Spur toothed gears are usually used for reverse gears as it not used frequently or for long periods and it also provide a less costly sliding gear engagement.
Helical toothed gears are used in most gear boxes due to there increased strength, durability, quietness and moderate cost.
Herringbone toothed gears are seldom used in automotive application due to their high cost and complexity.