Dismantling & Assembling of Gear Box - Sliding Mesh, Constant Mesh & Synchromesh Gear Box, Transfer Case

Aim

To study, dismantle, inspect and assemble the given Gearbox assembly.

Tools and equipments:

1.Hammer 2. Tool set 3. Screw Driver 4. Sockets. 5. Spanner set 6. Pullers

Function:

A machine consists of a power source and a power transmission system, which provides controlled application of the power. The term transmission refers to the whole drive train, including clutch,

Gearbox,

Propeller shaft (for rear-wheel drive), differential, and final drive shafts In motor vehicles, the transmission generally is connected to the engine crankshaft via a flywheel and/or clutch and/or fluid coupling. The output of the transmission is transmitted via driveshaft to one or more differentials, which in turn, drive the wheels.

Study: Gear Box

Often transmission refers simply to the gearbox that uses gears and gear trains to provide speed and torque conversions from a rotating power source to another device.

Principle::

• Gear box contain gearing arrangement to get different speeds.
• Gears are used to get more than one speed ratios.
• When both mating gears have same number of teeth, both will rotate at same number speed.
• But when one gear has less teeth than other, the gear with less number of teeth will rotate aster than larger gear.
• In a typical car, there may be six gears including one reverse gear.
• First gear gives low speed but high torque.
• Higher gears give progressively increasing speeds.
• Gears are engaged and disengaged by a shift lever.

Types of gear boxes:

Manual transmission

• Sliding mesh gear box.
• Constant mesh gear box
• Synchromesh gear box without overdrive.

Dismantling:

Given- Gear box assembly (Manual- constant mesh type)

• Mount the gear box on the work stand and remove the selector assembly.
• Lock the main shaft by engaging only two gears by shifting the respective slipping sleeve on the gear.
• Remove the locking pin and driving flange kit.
• Pull out the flange by using driving flange puller.
• Remove the gear box rear.
• Remove the speedometer drive gearbox from the main shaft.
• Remove the gearbox screw rear.
• Remove the driveshaft and lay shaft end cover.
• Drive the lay shaft, place the drive shaft puller. Place distance pieces on the gear casing below the puller bolt. Ensure that the distance piece do not sit on any threaded hole of the gear casing.
• Remove the main shaft from end nut and remove the pilot bearing.
• Tighten the bolt from the main shaft rear end bearing comes out of gear housing.
• Pull out the main shaft along with the bearing.
• Remove the main shaft from the gear casing.
• Remove the main shaft gear bushes, fixed dog clutch & sliding dog clutch.
• Remove the reverse idler gear shaft lock, shaft and idler gear.
• Remove the lay shaft gear set with the thrust washer.
• Remove the circlip from the drive shaft.
• Place the drift on the bearing & press drift from top till bearing out of drive shaft.

Inspection:

• Clean all the components.
• Check the parts visually for damages due to wear. - Measure the clearance between the bushes, & their respective gears are placed by bush gears.
• If the clearance found is more than specific limit, measure the clearance found more than projection of the bush & above the gear.

Assembling:

• Place the oil seal in the rear end cover & place the drift on the oil seal.
• Press the oil seal in the cover by the drift & fix it.
• Mount the gear box casing on the stand & lower down the lay shaft gears in the gear casing.
• Clamp the lay shaft in its position temporarily.
• Fix the lever idler gears along with the shaft & level it. Clean all tools and return them to

Result:

Thus the dismantling and assembling of Gear box have been performed.

Viva Questions:

1. Explain clearly the necessity of a transmission in a vehicle
2. Discuss the advantages of a constant mesh gear box over the sliding mesh type gear box
3. Describe the working of a synchromesh gear box with the help of a neat sketch
4. What is transfer box ? where it is used ?
5. What are the merits and demerits of synchromesh gear box compared to a sliding mesh on constant mesh type
6. Explain the common troubles encountered in gear boxes and suggest suitable remedies
7. What is a synchronizer
8. Why is synchromesh device usually not employed for the reverse gear
9. What may be the possible reason when the gear slips out of engagement
10. What should be the cause when the vehicle is running with excessive noise in the gear box