Page 1

3. GEARSHIFT CONTROL MECHANISM

Having studied the clutch in the previous lesson, the next component in the power train is the transmission gearbox. Before dismantling the transmission gearbox, however, it is instructive to see first how the gearshift control mechanism in the car is removed, dismantled, inspected, installed and adjusted. The adjustment of the gearshift control mechanism is important for proper meshing of the gears. The maintenance and overhaul of the transmission gearbox will be studied in two steps – first, the gearshift mechanism and then, the transmission.

3.0

Objectives After going through this lesson you will be able to: Remove, dismantle, and re-assemble the gearshift control mechanism. Adjust the gearshift control mechanism for proper meshing of gears.

i. ii.

3.1

Removal and Dismantling

The removal of the gearshift control mechanism from the car starts with the removal of the gearshift control lever.

Fig. 3.1: Gearshift control lever.

• •

Remove the four gearshift control lever housing nuts with the help of a No 12 socket and handle. Lift off the front strip and the clamping ring.


Fig. 3.2: (a) Removal of lever cover. (b) Removal of boot from gear lever.

The clamping ring is also known as the lever cover. • • • • • •

Unscrew the gear lever knob. Remove the boot from the gear lever. Remove the two bolts of No 10 size that hold the lever housing to the guide plate. Lift the car with the help of hydraulic jack and support it on safety stands. Remove the shaft joint bolt connecting the control shaft and the gearshift shaft on the transmission side, in order to remove the gearshift control shaft. Remove the control shaft rear bolt that joins the control shaft with the gearshift lever.

The movement of the gearshift lever is transmitted to the transmission case by the control shaft. The transmission case has three fork shafts, which are actuated selectively to shift the gear.

Fig. 3.3: Control shaft.

Remove the control shaft and place it aside.


Fig. 3.4: (a) Extension rod. (b) Removal of extension rod from bracket bolt.

• • • • •

Open the four bolts holding the extension rod plate to the guide plate. Unscrew the nut holding the other end of the extension rod to the bracket. Push the extension rod out from the bracket bolt and remove the extension rod. Pull out the gearshift lever downwards along with the guide plate. Remove the lever housing.

Fig. 3.5: (a) Gear shift lever and guide plate. (b) Lever housing.

Fig. 3.6: (a) Control shaft rear boot. (b) Extension rod bush.


Fig. 3.7: (a) Control shaft joint. (b) Components of gear shifting mechanism.

• • • • •

Remove the control shaft rear boot from the gearshift lever. Remove the dust seal from the gearshift lever. Remove the extension rod bush from the extension rod. Unscrew the nut holding the control shaft joint to the control shaft. Remove the control shaft joint.

The various components of the gear shifting mechanism dismantled include the gearshift lever knob, gearshift lever, lever cover, lever boot, dust cover, lever housing, lever seat cover, dust seal, guide plate, extension rod, gearshift control shaft, extension rod bush, control shaft joint, control shaft rear bush and the extension rod mounting bracket.

3.2 • • •

Inspection Check that the threads on the gearshift lever and in the knob do not slip. Check the boot for cracks. Inspect the seat of the gearshift lever. It should be smooth and shiny and without any evidence of abnormal wear.

Fig. 3.8: (a) Inspection of threads on the gearshift lever and on the knob. (b) Inspection of the boot for cracks.


Fig. 3.9: (a) Seat of the gearshift lever. (b) Damaged and new lever housing.

Check the end of the gearshift lever for wear. Inspect the dust cover and replace if damaged. • Check the lever housing and replace with new if found damaged. • •

Fig. 3.10: (a) Damaged and new rear boots. (b) Guide plate.

• • •

Inspect the rear boot and replace it with a new one if required. Inspect the lever seat cover and the dust seal for cracks or any other damage. Inspect the guide plate threaded holes. The threads should be in a good condition.

Fig. 3.11: (a) Extension rod bush. (b) Control shaft joint.


• • • • • • • •

3.3 • • • • • • •

Inspect the extension rod and its bush for wear and damage. Check the two control shaft rear bushes and replace if damaged. Check the control shaft bolt for damage or wear. Check the gearshift control shaft fork ends for wear. Inspect the control shaft joint for wear. Fit new O-rings on the control shaft joint. Inspect the joint bolt and replace with a new one if needed. Check the extension rod bracket bolt and replace if worn or damaged.

Assembly Apply SERVOGEM-3 grease to the seat and seat cover of the gearshift lever. Slide the seat cover over the lever onto the seat. Place the lever housing over the seat cover. Place the dust seal from the bottom end of the lever after applying grease. Place the guide plate over the dust seal and hold it by two bolts screwed in the lever housing. Tighten the bolts of No 14 size using a socket and ratchet handle. Mount the control shaft rear boot over the lever end and mount it properly over the guide plate.

Fig. 3.12: (a) Sliding the seat cover over the lever. (b) Sliding lever housing over the seat cover.

Fig. 3.13: (a) Placing dust seal. (b) Placing guide plate over dust seal.


Fix the extension rod plate to the guide plate by four bolts of No 10 size and tighten them with a ring spanner.

Fig. 3.14: (a) Mounted control shaft rear boot. (b) Fixing extension rod plate to guide plate.

The oval slots in the extension rod plate help to set the gearshift lever in the correct position for proper meshing of the gears.

Fig. 3.15: (a) Fixing control shaft rear bush. (b) Fixing gearshift control shaft fork extension.

• • • • • •

Fix the two control shaft rear bushes. Fix one end of the gearshift control shaft to the lower end of the gearshift control lever with the help of a bolt and nut. Tighten the nut with a No 10 open end spanner by holding the bolt head by a ring spanner. Apply grease to the extension rod bush and insert it in the extension rod. Fit four new O-rings in the control shaft joint and fix the joint to the gearshift control shaft fork. Check free movement of the joint after tightening the nut.


Fig. 3.16: (a) Fitting O-rings. (b) Fixing dust cover over lever housing.

• • •

Adjust the position of the gearshift lever by moving the guide plate forward or backward, so that each shift stroke is equal. This should be done while the lever housing nuts and the guide plate bolts are loose. Fix the dust cover over the lever housing. Slide the lever cover and boot over the gearshift lever on the dust cover. Screw in the gearshift control lever knob on the gearshift control lever.

Fig. 3.17: (a) Sliding the lever cover and boot. (b) Screwing in the gearshift control lever knob.

3.4

Installation and Adjustment

The components of the gearshift control mechanism, such as the gearshift control lever housing, extension rod and the guide plate are of the suspended type so that the engine vibration does not get transmitted to the gearshift control lever. To perform the installation of the gearshift control mechanism in the car, the following sequence of steps is followed: • Fix the lever housing by inserting the four studs provided on it into the holes in the floor of the car. • Screw the two nuts on these bolts with a socket and ratchet handle and secure it to the floor of the car. • Slide the lever seat cover over the gearshift lever and place on the lever seat.


Insert the gearshift lever from the bottom into the lever housing.

Fig. 3.18: (a) Lever housing in the floor of car. (b) Gearshift lever inserted into lever housing.

• •

• •

Fix the dust seal on the lever seat. Place the guide plate on the lever housing and secure both of them with the help of two bolts tightened with No 14 socket and ratchet handle from the other side. Fix the rear end of the extension rod over the guide plate and the other end to the extension rod mounting bracket. Screw in the four bolts lightly to fix the extension rod plate to the guide plate.

These screws are tightened after the adjustment of the gearshift lever position.

Fig. 3.19: (a) Fixing front end of the extension rod to the bracket. (b) Fixing control shaft at the rear end.

• • • • • • • •

Fix the front end of the extension rod to the bracket. Fix the control shaft rear boot at the bottom end of the control lever. Insert the two control shaft rear bushes in place. Fix the control shaft at the rear end. Place new O-rings in the control shaft joint. Fix the control shaft joint to the front end of gearshift control shaft. Fix the front end of the control shaft along with the joint to the gearshift shaft on the transmission side with a No 10 bolt and nut. Tighten the two bolts of the lever housing.


Adjust the gearshift lever position by displacing it towards the front and the rear so that each shift stroke is equal.

If the position of the gearshift lever is not adjusted properly, the gears will not mesh completely. Also, when the gearshift lever is brought into the neutral position, it should be in such a position along the lever select direction that it can be directly moved in either the “third” or “fourth” gear position. This is not the case when the gearshift control shaft bushings are worn. • • • • •

Tighten the two nuts of the lever housing. Place the dust cover, lever cover and the lever boot in place and secure them by tightening the rest of the two nuts. Tighten the lever knob on the gearshift lever. Test the gear shifting mechanism for smooth operation. Tighten the bolts securing the extension rod plate to the guide plate fully, if the shifting of gears is found satisfactory. This completes the assembly of the gearshift mechanism in the car.

Self-check Questions 1. ___________grease is applied to the seat and seat cover of the gearshift lever. 2. The position of the gearshift lever is adjusted by __________________, so that ______________________________. This should be done while the __________________________________are loose. 3. Name the components of the gearshift control mechanism which are of the suspended type so that the engine vibration does not get transmitted to the gearshift control lever. 4. When the gearshift lever is brought into the neutral position, it should be in such a position along the lever select direction that it can be directly moved in either the ___________ or __________ gear position.

3.5

Activity Go to a car and practice shifting the gears.

3.6

Summing Up

In this lesson, we learnt how to dismantle and reassemble the gearshift control mechanism. For the sake of clarity, the components were assembled first and then installed in the car one by one. When the components are removed, it is advisable to inspect the boots, dust seals and bushes for damage and wear and replace them if necessary. Dust, etc. should not be let into the gearshift control mechanism components, in order to have a long life.


In the next four lessons, we will study the transmission that is the gearbox, and the differential. These are assembled in one compact unit in the case of a Maruti 800 car engine.

3.7

Possible Answers to Self-check Questions

1. Servogem-3 2. moving the guide plate forward or backward, each shift stroke is equal, lever housing nuts and the guide plate bolts 3. gearshift control lever housing, extension rod, and the guide plate 4. third, fourth

3.8

Terminal Questions

1. Give the procedure of assembly of the gearshift mechanism.

3.9

References

1. Maruti 800 Service Manual

3.10

Glossary

Gearshift control mechanism

Linkage by which the gears in an automobile transmission are engaged and disengaged

O-ring

Endless rubber ring used as a sealing ring between two mating parts

104-L-3  

3.1 Removal and Dismantling 3.0 Objectives The removal of the gearshift control mechanism from the car starts with the removal of the gearsh...

Read more
Read more
Similar to
Popular now
Just for you