6. TRANSMISSION ASSEMBLY
In continuation of inspection of components that we studied in the previous lesson, we will learn how to assemble the countershaft and install the gear shifting and gear selector mechanisms in the transmission. After assembly, the backlash between the mating gears is to be checked and ascertained that it is within limits. If it is not so, the gears have to be replaced. If the assembly is done carefully, taking due precautions, the transmission will provide noiseless and trouble-free service.
6.0 Objectives After going through this lesson you will be able to: Assemble the countershaft Install the shifting mechanism in the transmission case Install the gear selector mechanism in the transmission case Assemble the transmission
i. ii. iii. iv.
6.1 Assembly of Countershaft • •
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Check the straight roller bearing. Apply oil on the journal of the straight roller bearing and slide it on the countershaft, keeping the groove of the C-ring away from the differential pinion side. Fix the lock pin in the hole and then slide the washer so that the cut in the washer comes over the pin. This prevents rotation of the washer. Apply oil on the second journal and slide the needle roller bearing over the shaft in place. Apply oil in the bore of the top gear and slide it over the needle bearing keeping the cone away from the pinion side. Put the synchronizer ring with its dog teeth towards the pinion side so that internal cone of the ring fits over the external cone of the top gear. Take the hub and fit the two synchronizer springs on either side in the hub. Do not deform or otherwise damage the synchronizer springs. Insert the hook end of the spring in the spring setting hole in the synchronizer hub to install the springs.
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Fig. 6.1: (a) Three keys in the hub. (b) Hub fitted in sleeve.
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Direct the 2 springs in opposite direction to each other so that the load is applied evenly on the synchronizer keys. Hold the three keys in the hub in the slots provided and fit the hub along with the keys into the sleeve as shown in the figure. Slide the hub and sleeve assembly over the countershaft so that the fork groove is towards the pinion. See that the three keys mounted on the hub fit snugly into the slots provided in the ring. Slide the washer over the countershaft so that the match marks on the hub and the washer face each other. Put the second synchronizer ring so that its three slots fit on the keys of the hub and sleeve assembly inserted earlier. Slide the splined bush on the countershaft so that the cut mark is towards the pinion side. Apply oil on the bush. Assemble the third gear over the needle roller bearing and slide them together over the splined bush keeping the gear cone towards the pinion side.
The outer surface of the splined bush acts as a journal for the needle roller bearing, so that the gear is free to rotate on the bearing independent of the counter shaft. • • • • • • •
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Place the washer on the gear. Place the anti-rattle spring on the gear. This spring prevents noise due to play. Insert the splined bush over the counter shaft so that its cut mark is away from the pinion side. Insert the needle bearing over the bush and then slide the second gear over the bearing so that its cone side is away form the pinion side. Place the synchronizer ring over the gear so that their cones match with each other. Install the spring between the low gear synchronizer ring and the synchronizer hub. Assemble the low speed synchronizer and slide over the counter shaft so that the chamfered end of the reverse gear points away form the pinion end.
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Insert the splined washer. Place the synchronizer ring matching the key slots with the keys in the sleeve. Slide a plain bush over the counter shaft. Apply oil to the outer surface of the bush and place a needle roller bearing over it. Place the first gear on the bearing and insert the steel ball in the hole provided in the shaft. Place the washer with the slot over the ball. Fit the ball bearing on the counter shaft keeping its groove end away from the pinion side. Insert the speedometer drive gear over the splines of the counter shaft and screw in the nut. Tighten the countershaft nut by fitting the special tool on the low speed synchronizer sleeve and fix it securely in a vice. Tighten the nut to the specified tightening torque of 6.0 to 8.0 mkg. Caulk the nut with a chisel over the groove in the countershaft to lock the countershaft nut firmly. A nut that has been used once should not be reused.
Fig. 6.2: Countershaft assembly.
The assembled countershaft will be placed in the transmission gearbox when the transmission is assembled, as we will see later.
Self-check Questions 1. 2. 3. 4. 5.
How is the gear on the countershaft free to rotate on the splined shaft? How is the countershaft nut tightened? What is the tightening torque of the countershaft nut? How is the countershaft nut prevented from loosening? How many times can the countershaft nut be reused?
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6.2 •
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6.3
Assembly of Idle Gear in Upper Case Wipe the idle gear shaft with a clean cloth and smear some oil on it, before pushing it in the case. Install the reverse idle gear in the upper case, placing the chamfered edges of the teeth towards the inside. Push the shaft so that the lock pinhole in the shaft matches the lock pinhole in the upper case. Insert the lock pin in the hole after applying grease so that the lock pin does not come out until the gear Fig. 6.3: Idle gear and shaft. case is assembled. Fix the end plug of the idle gear shaft. Check for free movement of the idle gear, both rotary and sliding.
Installation of Reverse Shifting Mechanism
The installation of the reverse shifting mechanism is begun by inserting the interlocking balls in their place in the lower case. The interlocking balls prevent any other gear getting meshed when one is already in mesh. Grease is applied before inserting the balls so that when the shifter fork shafts are inserted later on, the balls stick in the holes and do not roll away. •
Insert one ball in the central hole and push it towards the right.
The ball on the right locks the low speed shifter fork shaft from sliding back or forth and from engaging the first or the second gear.
Fig. 6.4: Shifting mechanism.
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Insert the second ball and push it towards the left.
The ball on the left locks the reverse shifter fork shaft and prevents it from engaging when any other gear is engaged. •
Insert a spring and a ball in each hole from above, one by one.
The spring-loaded balls lock the shifter fork shafts in position after a gear has been engaged so that it does not slip out of engagement. • •
Fix the reverse gear shifter fork by holding it to the lower case. Tighten the bolt by a No 14 ring spanner. The gap between the face of the lever and the case should be 5 mm.
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6.4 • •
Apply oil to the reverse shifter fork shaft and insert it in the case taking care to see that the spring-loaded ball is first pushed inside and the shaft rides over it. Place the shift fork lever and reverse gear shifter block and push the shifter fork shaft inside until it enters the gear case on the other side. Lock the lever to the shaft with an 18 mm long pin by hammering the pin with an installer and hammer. Lock the shifter block to the shaft by a 20 mm pin. Insert the stopper pin in the shaft.
Assembly of Shifting Mechanism for Third & Top Gear Apply oil to the high-speed shifter fork shaft and fix the interlocking pin in the shaft groove. Insert the shaft in the gear case taking care to see that it rides over the springloaded ball.
It must be ensured that the interlocking ball is in proper position between the two shafts, that is, the reverse gear shaft and the high-speed shifter fork shaft. • • •
6.5 •
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Insert the high-speed shifter fork and push the shaft forward. Lock the fork to the shaft by fitting a 20 mm lock pin. Fit the 18 mm stopper pin on the other side.
Assembly of Shifting Mechanism for First & Second Gear Apply oil on the low speed shifter fork shaft and insert it in the hole taking care to see that the spring-loaded ball goes below the shaft and the interlocking ball is placed between the high-speed shaft and the low speed shaft. Place the shifter block and the shifter fork on the shaft. Push the shaft until it rests in the hole on the other side in the case. Fix the fork and the block to the shaft by lock pins. Fix the stopper pin in the shaft. Fix the three end plugs in the shaft holes after applying Suzuki Bond 1215.
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Self-check Questions 6. The installation of the reverse shifting mechanism is begun by inserting the ____________________ in their place in the lower case. 7. What is the function of the interlocking balls? 8. What is the function of the spring loaded balls inserted below the shifter fork shafts? 9. How are shifter forks and blocks fixed to the shafts?
6.6
Installation of Gear Selector Mechanism
The lower case is turned up to fit the gear selector mechanism. •
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Insert the boot over the gear selector shaft and push it in the case so that the lock pinhole in the shaft and the hole in the block coincide. Fit the lock pin. Apply Suzuki Bond to the selector mechanism plate and fit it in place with the help of five screws of No 10 size, taking care to see that the plate is placed properly so that the gear selector mechanism lever rests in the recess provided in the plate.
Fig. 6.5: C-ring.
This completes the lower case assembly on one side.
6.7 • • • • • • • •
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Placement of Gear Assemblies in Lower Case Fix the C-rings in place in five locations in the lower case. Place the input shaft in its proper place. Place the countershaft assembly taking care to see that the gears mesh properly. Check for free rotation of the two shafts. Place the differential unit and see that the final gear meshes with the final drive pinion on the countershaft. Check the assembly for free rotation. Check the backlash between the gears with the help of a dial gauge. Fix the clutch fork shaft in its proper place.
6.8 •
Fixing the Lower and Upper Cases Apply Suzuki Bond No 1215 over the matching faces of the lower case and the upper case before bringing them together.
It must be ensured that the clutch fork shaft is held in the lower case and the idle gear is installed in the upper case. • • •
Place the upper case over the lower case, making sure that the reverse idle gear fits properly in the reverse fork lever. Tap the upper case with a plastic hammer for proper fitment. Insert all the eighteen bolts in their proper places.
The bolts are of unequal length. Also, one bolt is of No 10 size and the remaining seventeen bolts are of No 12 size. •
6.9 • • • • • • • • • •
Tighten the bolts holding the lower case to the upper case in the prescribed sequence.
Assembling and Remounting the Transmission Place the oil seal over the side bearing. Fit the end plugs over the countershaft and the input shaft of the transmission with a plastic hammer. Insert the oil gauge. Insert the speedometer gear bush and lock it with a bolt. Install the second oil seal over the other side bearing. Fit the end plug on the countershaft-bearing retainer at the clutch side after applying Suzuki Bond No 1215. Ride the spring over the clutch fork. Fit the input shaft bearing retainer by four screws with a Philips screwdriver. Tighten the bolts holding the upper case to the lower case to the specified torque of 7.5 mkg. Fit the clutch release fork arm along with the spring.
The clutch release arm should be fixed to the clutch release shaft in such a way that the punch mark on the clutch release arm is shifted towards the front side by one notch from the punch mark on the clutch release shaft. • • • •
Tighten the nut. Apply grease on the inside of the release-bearing retainer. Fit the release bearing along with the retainer over the fork. Check for free movement of the release bearing over the gearbox input shaft.
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Mount the transmission on the engine.
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Self-check Questions 10. ________________ is applied to the selector mechanism plate before screwing it down. 11. How many C-rings are used in the transmission case? 12. How is backlash between the gears checked? 13. The clutch fork shaft is held in the __________and the idle gear is installed in the___________. 14. ___________________ is applied over the matching faces of the lower case and the upper case before bringing them together. 15. What must be ensured before the upper and lower cases are brought together? 16. The bolts holding the upper case to the lower case are tightened to specified torque of ___________ 17. The clutch release arm should be fixed to the clutch release shaft in such a way that __________________________________________________
6.10
Summing Up
In this lesson, we studied the assembly of the countershaft and indeed the whole transmission. Before fixing the upper and lower cases we placed the differential unit in the transmission. Now in the next lesson we will dismantle the differential unit, inspect its components and re-assemble. The rest of the procedure for dismantling and re-assembling the transmission will be the same.
6.11
Possible Answers to Self-check Questions
1. The outer surface of the splined bush acts as a journal for the needle roller bearing, so that the gear is free to rotate on the bearing independent of the counter shaft. 2. Tighten the countershaft nut by fitting the special tool on the low speed synchronizer sleeve and fix it securely in a vice. 3. 6.0 to 8.0 mkg 4. Caulk the nut with a chisel over the groove in the countershaft to lock the countershaft nut firmly. 5. A nut that has been used once should not be reused. 6. interlocking balls 7. The interlocking balls prevent any other gear getting meshed when one is already in mesh. 8. The spring-loaded balls lock the shifter fork shafts in position after a gear has been engaged so that it does not slip out of engagement. 9. by lock pins 10. Suzuki Bond 11. 5 12. with the help of a dial gauge 13. lower case, upper case 14. Suzuki Bond No 1215
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15. It must be ensured that the clutch fork shaft is held in the lower case and the idle gear is installed in the upper case and that the reverse idle gear has been fit properly in the reverse fork lever 16. 7.5 mkg 17. the punch mark on the clutch release arm is shifted towards the front side by one notch from the punch mark on the clutch release shaft
6.12
Terminal Questions
1. Explain the purpose and installation procedure of interlocking balls and spring loaded balls.
6.13
References
1. Maruti 800 Manual
6.14
Glossary
Anti-rattle spring
Spring designed to eliminate unnecessary rattle. Used in some types of clutch and on many of the modern disc-brake systems.
Backlash
Clearance between the meshing teeth of two gears
Countershaft
A shaft in a manual transmission that is below the mainshaft. Also called a lay shaft or cluster shaft. The gears on the countershaft are called cluster gears or counter gears.
Dogs
Mating blocks or protrusions forming part of a dogclutch.
Idle gear
Additional gear in a train, its purpose being to reverse motion or connect shafts some distance apart without using gear wheel outside large diameter.
Journal
Part of a shaft in contact with a bearing.
Key
Small block of metal which fits into grooves cut in two components of an assembly (e.g. a gear wheel on a shaft) and locks them together.
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Pinion
Generally, the smaller of a pair of gears. Commonly used to describe the smaller of the final-drive gears (crown wheel and pinion) or the starter-motor gear that engages the flywheel to turn the engine.
Selector mechanism
Mechanism of the gearbox, operated either by hand or automatically, that selects a desired gear.
Splines
Grooves along a shaft and in a component carried on it; they can allow longitudinal movement between the two, but lock them together for rotational movement.
Synchronizer ring
Gunmetal ring with internal cone interposed between the gear and sleeve to synchronize their speeds