Synchromesh gearbox assembly procedure

Synchromesh gearbox assembly procedure

One of the main advantages of a manual transmission over an automatic transmission, beyond the more-involved driving experience, is that they are very simple to use, fix, and rebuild.

There generally are very few things you can do to make them better other than make them stronger if you intend to race them. I highlight important areas that need to be given some extra attention when rebuilding such a tranny, in this case the Toploader that was available for our GT. I show some of the major steps involved in taking this transmission apart and putting it back together again.

We again relied on Big 4 Transmissions of Paramount, California, to share some of their expertise with working on this type of transmission. One of the most useful tools needed when rebuilding a manual transmission is a pencil magnet, such as this one. As you remove these small parts, make a note of where they came from, so they go back in the right place.

Many of the larger external parts of the transmission can be removed at the beginning of the process. These will include the shift linkage, the tranny mount, the top cover, and the input bearing collar, as is shown here.

Inspect it for excessive wear or damage on the surface where the throughout bearing slides. Remove minor scratches with emery cloth, but any significant flaws mean replacement of the part. The shaft seal on the inside of the collar will be replaced; these have a tendency to harden with time and can thus develop a leak. During the disassembly of a manual transmission, many small parts, such as detent pins and so on, need to be removed for access to other parts.

There are also situations in which parts such as shafts need to be oriented to a certain position before they can be removed. The factory service manual generally describes these procedures in detail. Look for of any pins or retaining rings that may have to come out before it can be removed.

synchromesh gearbox assembly procedure

Also try rotating the part to different positions to see if that solves the problem. Lots of force should not be needed to remove the vast majority of components except for bearings. Look for any signs of wear or surface damage when removing the various support shafts. While it is rare, pitting or galling has occurred under some circumstances.

Minor imperfections can be removed with a fine emery cloth or pad, and the parts can then be rinsed in the parts washer to remove any residue.Sst — —, —, —, —, —, —— — Sst — —, —, —, —, —— — Remove bearing retainer rear mtm.

Hint : using a waste to prevent the snap ring from being scattered. Remove input shaft assy. Sst — —, — Remove front transaxle case oil seal. Sst — —, — Sst — —— — Remove fr differential case rear tapered roller bearing. Inspect synchronizer ring no. If the braking effect is insufficient, apply a small amount of the fine lapping compound between the synchronizer ring and gear cone.

Lightly rub the synchronizer ring and gear cone together. Notice : ensure the file lapping compound is completely washed off after rubbing. Minimum clearance: 0. If the clearance is less than minimum, replace the synchronizer ring and gear cone by applying a small amount of the fine lapping compound on gear cone. Notice : ensure the fine lapping compound is completely washed off after rubbing. Standard clearance: 0. If the clearance is out of specification, replace the transmission hub sleeve no.

Notice : install the output shaft mtm cover projection into the case side hollow. Sst — —— — Notice : be sure to install a new bearing in the correct direction, as shown in the illustration. When replacing the output shaft front bearing, replace the output shaft front bearing inner race along with it.

Sst — —— — drive in depth: Install input shaft front bearing. Sst — —— — drive in depth: 0 — 0. Install fr differential case front tapered roller bearing. Sst — —— — Install fr differential case rear tapered roller bearing.

Sst —, — —— — Hint : use a shim of the same thickness with the removed one. Torque: Sst — Sst — preload at starting : new bearing: 0. Vlbf If the preload is out of specification, select another shim. Hint : the preload will change by about 0. Vlbf corresponding to a change of 0.Before decoding synchromesh and dog gearboxes, it is critical to understand the beast. Most modern cars are fitted with a synchronized engagement gearbox from the factory to deliver smooth, reliable, and quiet operation, which is paramount for a daily driven vehicle.

Synchromesh transmissions operate using a collar that applies force to a cone-shaped clutch attached to the gear. Synchromesh gear engagement is best at lower engine speeds and requires a bit more time compared to a dog box, to facilitate shifts. Limitations of synchromesh gearboxes in high-performance applications include slow upshifting at very high engine speeds—e. Dog engagement is normally used in racing applications where fast, precise shifting is needed.

Dog gear engagement is facilitated by numerous large teeth dogs that mate into matching openings machined into the opposite surface of the drive gear. Unlike the synchro engagement, there is no synchronizing mechanism to assist in equalizing speed. Ideal gear selection—e. There is no depressing the clutch in the conventional sense like with the synchromesh transmission.

A momentary break in engine load until the shift is achieved by a quick throttle blip or clutch depression.

Gearbox Beatdown - Synchromesh vs. Dog Box

The driver will then experience the dog ring engaging with the next gear and the throttle can be reapplied. With practice this can be done in milliseconds.

In fact, a driver can preload the stick shift in the direction of the next shift, and then when he either blips the throttle or clutch the shifter will quickly click in the desired gear. With all else equal, dog-engagement gears are much stronger than synchro-engagement gears because without needing to make space for synchro rings, the gears themselves can be made thicker.

The number of dogs teeth and the size of the openings determine the window of opportunity that the dogs have to engage during the shift event.

Rings with a smaller number of teeth provide a more efficient, smoother shift quality. The downsides to this easier engagement are increased noise and abruptness on the shift.

synchromesh gearbox assembly procedure

This involves slow shifting and use of the clutch—i. The belief that dog boxes inherently feature straight-cut gears is a long-standing misconception. In fact, either type of gearset can be fitted with straight cut—also known as spur—gears as well as conventional helical-cut gears. The cut of the drive gear is a separate characteristic of the gearbox and does not affect the engagement of the gears.

Dog engagement can be introduced to a stock gearbox by swapping gearsets. Aftermarket dog sets are usually made of higher-grade material and feature bigger, stronger teeth, and better profiles. Albins Gear, located in Australia, has moved to the forefront of the dog-box revolution, offering a wide range of dog-engagement gearsets as well as fortified synchro sets for Honda, Porsche, Nissan, Subaru, Mazda, VW, and Mitsubishi applications.

Albins dog gears are verified using a robotic CMM coordinate measuring machine to assure perfection with tolerances better than 0. Furthermore, Albins has been able to produce its own proprietary steel alloy with a consistency far superior to mass-produced, low-cost sets.

Notice the thicker gears and teeth of the Albins unit below and the cuff that replaces Fifth gear unneeded in the quarter-mile and ties the two shafts together for added strength. Here is the big difference between synchro and dog boxes. The synchromesh ring left uses a cone that a brass clutch ring pushes against to equalize the speed between the gear and the input shaft to ease gear engagement. Once this happens, the small pointed teeth around the perimeter deflect off the engagement ring and allow the slider to engage the gear.Home Capabilities Overhaul and Repair Procedures.

All speed reducers or assemblies will be: Completely disassembled. Hot Tank Stripped. Cleaned, wire brushed of all rust and grease. Cases, housings, etc. Summary of required procedures to return reusable parts to print specification. Summary of price for labor and all materials to complete the job. You must approve repair prior to any work proceeding. QRS will give a one-year warranty when we have replaced all parts, bearings, and seals as recommended in our quote.

If the job is not awarded to QRS, compensation for disassembly labor, cleaning, inspection, and freight will be made to Quality Reducer Service, Inc. QRS Repair Specifications: 1. Shafting Repair may be made by plating and grinding, or machining and sleeving. Will be straight and finished in accordance with tolerances and finish specifications as indicated on appropriate drawings. New shafting provided will match the specifications and dimensions of the original part as per customer print. Exposed threads, shaft ends and couplings will be protected with an anti-rust protection coating prior to shipping your Gear Box.

Gearing Will be dimensionally inspected to customer prints, manufacturers' prints, or reverse engineered. See attached literature from our gear manufacturing facility, Circle Gear, Inc. New gearing provided will meet or exceed the specifications and dimensions of the original parts as per customer print. Cases, Housing, etc. Bolts, studs, and pipe fittings may be reused if in good condition.

Replacement bolts, studs, and pipe fittings will be of equivalent grade and material unless otherwise specified. Customer must approve any print modifications prior to implementation. Assembly and Test Procedures All seals, shims, and gaskets will be replaced All bearings will be replaced. All hardware will be reused or replaced depending upon condition. All repaired and overhauled units will be run tested to check contact patterns, clearances, backlash, and freedom of movement.

When pressure lubricated units are involved, QRS will pressure test the unit when applicable. Painting and Identification All speed reducers will have: Exterior surfaces cleaned of all loose scale and rust. Entire Housing surfaces cleaned of all dirt and oil. One coat of light blue enamel applied on the exterior, unless otherwise specified by the customer. A new identification tag will be installed to each overhauled speed reducer with the following information: Date overhauled Our job number Your purchase order number 7.

Shipment All openings are properly protected with plugs or cover. All units are shipped dry from QRS The unit shall be marked to indicate that lubricant must be added prior to operation. Run Test Procedure Firmly mount gearbox to be tested to run test stand. Fill the unit with QRS Company run test lubricant. Attach the oil pumping station to the unit if required. Hook up all run test equipment. Check and document temperature.When selecting reverse, the direction of rotation of the output shaft is changed This is achieved by using an idler gear.

Full Notes on Synchromesh Gearbox

The idler gear is meshed between a counter shaft gear layshaft or 2 nd motion shaft and an output shaft gear mainshaft or 3 rd motion shaft. Design of Transmission Systems. Search this site. Author Davis Hans S J. Feedback and Suggestions. Flat Belt. V Belt.

Manual Transmission, How it works ?

Chain Drive. Wire Rope.

How Does A Synchromesh Work?

Constant Mesh Gear Box. Sliding Mesh Gear Box. Bevel Gears. Helical Gears. Spur Gears. Worm Gears. An obsolete type of transmission or gearbox in which the gears on the layshaft are fixed to the shaft rigidly, whereas the gears on the main shaft can slide on it by means of splines but are otherwise in permanent rotational mesh with the shaft.

The figure below shows the arrangement of sliding mesh gear box. Sliding mesh gear boxes are made with spur gear. The gears in the layshaft is rigidly fixed shaft. A idler gear is provided for reverse gearing. Second gear. Construction and working of sliding mesh gear box Sliding mesh gear boxes are made with spur gear.

First gear In the first gear, the gearbox provides maximum torque at low speed. Reverse gear When selecting reverse, the direction of rotation of the output shaft is changed This is achieved by using an idler gear.Gearboxes are crazily complicated wonders of mechanical engineering that have allowed petrolheads to continually accelerate their vehicles by using a bunch of varying diameter cogs. Problems then arise from the fact that these gears all have teeth which protrude around their outer circumference which are essential for transmitting the power from the engine to the wheels through the transmission.

If these teeth are not aligned perfectly, the gears on the output shaft will crunch with the gears on the layshaft, which could potentially lead to broken teeth and an expensive bill. The alignment between the gears within the transmission all depends upon the speed they are spinning at; if you get gears spinning at the right speed, the teeth will mesh together and be capable of transmitting power through to the driveshafts and the wheels.

Back in the day, the art of rev-matching and double declutching were used to change gear efficiently, but the invention of the synchromesh changed the manual transmission as an entity forever, simplifying the gear-changing process. There are three main parts to the synchromesh action — the gear that is asked for, a bulk ring and a synchromesh unit.

The bulk ring has outer teeth that mesh with the synchromesh teeth, but it also has an inner groove pattern that meshes with the gear that is required to be engaged. The synchromesh has an inner spline that coincides with the output shaft and then an outer spline that allows an inner ring to move internally within the gear.

This outer ring is designed to only mesh with the bulk ring once their speeds are matched, meshing the teeth together. So, as you begin to select a gear with the gear linkage, the selector forks initiate pressure on the bulk ring, which then begins to close in on the main selected gear. Luckily the gear has a cone-like shoulder on it which causes friction with the bulk ring which also contains a sleeve perfectly shaped to accept the shoulder, slowing the gear down.

Soon, the bulk ring and gear are moving at the same speed and in perfect harmony. With added force applied as the physical shift is performed through the linkage, the synchromesh unit is slid over the bulk ring, with both rotating at the same speed.

The inner ring of the synchromesh then allows the outer radius of the synchromesh to meet up fully with the main gear, synchronising their motion together and completing the gear change smoothly. A synchromesh effectively allows a gear change to be completed with one actuation of the clutch through the clutch pedal, essentially forcing the rev-matching through its efficient teeth-meshing.

Instead of having to match the speed of the clutch plate and fly-wheel, the synchromesh does all the work slightly further down the line and has made manual gear-shifting far easier than it once was.

We take for granted how well car transmissions do their job these days, especially with the levels of engine power now being forced through modern gearboxes. But synchromeshes are like the ligaments of a car, connecting the transmission of power smoothly from one muscle to the rest of the body seamlessly. So next time you slam a last-minute shift just below the red-line and the gear slots into place smoothly, remember that some genius engineering was key to that enjoyable shift action.

Please confirm you agree to the use of tracking cookies as outlined in the Cookies Policy. Sign in or register. Michael Fernie 4 years ago Remind me later. Share Tweet Email Whatsapp. A gear synchroniser from a Jeep, showing the inner and outer splines.

Back in the day, having to depress the clutch twice - known as double declutching- was the norm. Sort by Best Sort by Latest. Show Comments.

synchromesh gearbox assembly procedure

Sign in to your Car Throttle account Before you sign in Please confirm you agree to the use of tracking cookies as outlined in the Cookies Policy. I agree.The gearbox assembly is kept on a workbench and the oil inside it is completely drained. The front cover, rear cover and end cover are removed.

Then the. The clutch shaft top gear shaft is removed along with the bearing. The pilot bearing is removed by removing the nut from the front end of the main shaft and then the gear units and synchromesh are removed in order. At last the main shaft is removed from the top. After removing both the bearings of the lay shaft, the shaft is removed. Then the reverse gear shaft is removed followed by the idler gears.

Cleaning: The components of the synchromesh gear box are thoroughly cleaned with kerosene. Inspect the front cover, rear cover, gearbox case and top cover clutch housing. The gears, bearings. Main shaft splines. Loading comments. Video is uploading Hari Haran 14 Oct More action Follow Hari Haran 0 Report. Add Comment. Share Recommended Posts Knowledge apps Artificial intelligence. Carrier in Forensic science. The upcoming Nasa space mission. Some interesting facts about Stephen Hawking.

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