GEARBOX REPAIR: what it involves, the cost and how to prevent it


Introduction     

  1. GEARBOX – INTRODUCTION
  2. CAUSES OF GEARBOX WEAR
  3. GEARBOX DIAGNOSIS
  4. GEARBOX REPAIR – WHAT DOES IT INVOLVE?
  5. GEARBOX REPAIR – A GARAGE OR DIY?
  6. WHAT IS THE COST OF GEARBOX REPAIR?
  7. ARE THERE ANY ALTERNATIVE SOLUTIONS?
    A) Replacing the gearbox with a second-hand one
    B) Application of Ceramizer® - transmission oil additive
  8. PREVENTATIVE MAINTENANCE

    


 

Introduction

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This guide refers to wear of the manual gearbox. Its purpose is to describe step by step, all of the operations involved in the repair (described precisely in your car owner’s manual). The guide presents the most important information on gearbox wear in a clear and simple way including:

  • Causes of gearbox wear.
  • Diagnosis of a faulty gearbox.
  • Steps involved in gearbox repair.
  • Gearbox repair costs.
  • Alternative solutions.
  • Preventative maintenance.

 

1. GEARBOX – INTRODUCTION

Gearbox – Principles of Operation

A transmission is also used on pedal bicycles and fixed machines, where rotational speed and torque needs to be adapted. A transmission often has multiple gear ratios (or simply “gears”) and offers the function of switching between them as the speed varies. Bicycles are usually provided with multiple-gear transmissions and switching  is done manually. Using chains and chain wheels that are smaller than the tires, many more revolutions can be attained with much less exertion from the cyclist. For example, the chain wheels might have 20 teeth, compared to the tires which are 25-inches in diameter. The rear gear might have 28 teeth. This creates a ratio that allows the tires to turn much more often, than would be possible with a single turn of the pedal.

A similar principle applies in case of an automotive manual transmission. Thanks to the proper arrangement of cogs, five or six gears and a reverse gear are available. The driver may also make use of the idle gear, when the car is not moving,  although the engine is operating.

The drive train includes the gearbox, clutch, prop shaft (for rear-wheel drive), differential and final drive shafts. In case of a car, you need a clutch because the engine spins all the time.  However, the car's wheels do not spin. That is why in order to stop a car without killing the engine, the wheels need to be somehow disconnected from the engine. The clutch allows us to smoothly engage a spinning engine to a non-spinning transmission, by controlling the slippage between them. The clutch is the mechanism for transmitting rotation, which can be engaged and disengaged.

 


2.    CAUSES OF GEARBOX WEAR CAUSES

What is the reason for gearbox wear?

The most common causes involve:

  1. Aggressive driving and improper shifting.
  2. Old oil or insufficient gearbox oil level.
  3. Driver errors –shifting into the wrong gear for the rate of speed and engine load.

 

Ad.1 Aggressive driving and improper shifting.

Transmission component wear is very often caused by driver’s errors, including improper shifting. This results in the striking of cogs against each other with a force that causes their premature wear.  

Because they are vulnerable, synchronizers suffer the most. It may also result in premature teeth abrasive wear or gear tooth pitting.

 manual transmission synchronizer, gear grinding fix
Figure  1.  Gear rack with synchronizer.

 

Ad. 2. Old oil or insufficient gearbox oil level.

One of the most overlooked parts of car maintenance is keeping your gearbox oil fresh and filled. The more the clutch and transmission works, the more the oil is subject to "shear". It loses its viscosity and results in the overheating of some components and their premature wear. Dirty or poor quality oil first results in synchronizer wear that initially very often goes unnoticed.

As heat destroys the fluid's lubricating qualities and friction characteristics, the “worn out” oil does not transfer heat away from the working componentsThis is particularly evident in the winter, when you need to use more force during shifting. The old oil is quickly subjected to solidification at low temperatures and  thins excessively at high temperatures.

How often should the oil be changed with a manual transmission? The oil should be changed at least as often as recommended by the manufacturer. For some cars, the oil change should be changed after reaching 60 thousand km. This type of maintenance is very simple. Some vehicles are provided oil that is intended for multi-year operation.   The manual for these vehicles does not recommend any more frequent change.  However, in practice, it is worthwhile to change the oil more often. This is especially true for vehicles which are between ten and twenty years old. The more frequent oil changes help to enhance transmission life.

Insufficient oil level in the gearbox is another reason for its premature wear. It is most often caused by gearbox leakage. Gearbox capacity is on average ~ 2l, and even a minor leakage can cause the gearbox to totally empty.

Do you remember the last time that you checked the gearbox oil level?


Ad. 3. Driver errors –shifting into the wrong gear for the rate of speed and engine load.

Shifting into the wrong gear for the rate of speed and engine load, also results in the premature wear of the gearbox bearings, due to their operation under extreme loads.
As a result, there is wearing of the metal balls and bearing cones that causes excessive play on the gearbox shaft and at the same time noisy operation. Continual operation of such a gearbox, may cause poor teeth alignment and gearbox damage.


3. GEARBOX DIAGNOSIS

Driving gives drivers much joy, provided that the car is in a good shape. That is why proper diagnosis is essential.

Some symptoms or minor defects that go unnoticed for a long time, may cause serious failure and put the car out of operation. It is possible for you to personally notice or hear some gearbox irregularities, if extra caution is given.  

The main irregularities that may indicate improper gearbox operation include:

  1. Oil leakage.
  2. Noisy operation of the gearbox.
  3. Grinding noise during shifting.
  4. Difficult or impossible shifting.

1. Oil leakage

At the beginning of the diagnosis, it is worthwhile to check the oil level. Even minor leakage, such as with the gearbox housing, half-shafts sealing or drain plug, may result in gearbox wear or put the car out of operation while traveling, which can cause expensive problems. Check for any leakage near the gearbox and engine, as well as half-shafts.

Regularly check your parking space for leaks when you pull away. If you see any leaks, get it fixed before lack of oil or fluids can cause expensive problems.

 gearbox transmission oil leak
Figure  2.  Visible gearbox oil leakage.

 

2. Noisy Gearbox operation

Another symptom that requires your attention is noisy gearbox operation.

Noisy gearbox operation is mainly caused by worn out bearings. In this case, noise is evident and noticeable when driving in any gear.

Sometimes noise or irregularities evident during driving in any gear, may indicate wear of the differential gear of the rear axle (rear drive and four-wheel-drive vehicles have a rear axle).

If noise follows at that particular gear, it may be caused by gear tooth pitting.

Sometimes noise may be evident when pressing on the clutch. This may be caused by worn clutch bearings. The bearing operation actually follows after pressing down on the clutch pedal.  This is why the noise does not follow after the release of the clutch.

 

3. Grinding noise and resistance during shifting

A grinding noise or resistance during shifting, very often indicates worn gear synchronizers. They are used to match up the speed of the two moving cogs inside your box. When you move the shift, it pushes/slides a cog onto another cog, and the gears engage. To make this a smooth transition, one cog which is usually cone shaped (tapered) and the other will slide on to it, like putting the cap on a pen, with both of them rotating.

During quick shifting (in particular at high revolution speeds), the worn gear synchronizer fails to synchronize the shaft and cog rotation. Grinding follows as a result.
Since each gear is provided with own synchronizer, a synchronizer failure usually relates to the particular gear ( such as grinding during shifting from one to two gear indicates two gear synchronizer failure).

 worn synchronizer, cause of gears grinding
Figure 3.  Worn gear synchronizer, which often results in grinding noise

 

Application of Ceramizer oil additive, in many cases, provides for the regeneration of synchronizers, prevents grinding and provides for smooth shifting.

In addition to grinding, resistance may also follow during shifting.

If this irregularity follows in any gear and only at low temperatures (with the hot oil grinding disappears), the reason might be improper gearbox oil. Sometimes, the solution might be to change the oil to the one recommended by the manufacturer ( usually a synthetic oil).

In the case of the gearbox oil change, the previously applied oil type is not a concern,  in contrast to the engine oil change. That is why you may apply any mineral or  synthetic oil. However, please note that applying synthetic oil may increase the leakage in the case of gearbox leakage.

However in any other case – if cost does not matter (synthetic oils are more expensive) – a synthetic oil is recommended. Mineral oils, at the beginning of operation, feature performance similar to the synthetic ones.  However, in the long run, they cannot compete with their performance. Synthetic oil ages very slowly and features better viscosity parameters.  It also has better quality and resistance to temperature fluctuations. As a result, the gearbox performance improves in winter and you can obtain fuel savings of up to 1-2%.

Difficult shifting in any gear may indicate a worn drive plate. As a result,  the clutch pedal disconnects from clutch disc at the very end, near the floor, or fails to provide for a total disconnection.

 

 gears shift hardly
Figure 4.  Difficult shifting may indicate a worn drive plate.

 

4. Difficult or impossible shifting

In the case of difficult or impossible shifting, it is worthwhile to check the engine/gearbox mountings (with possible transfer of vibrations to the car body) or the play.

 Gear shift problems
Figure 5.  Impossible shifting may be caused by damaged mountings of the engine or gearbox.

 

Difficult shifting during driving may also be a sign of significant wear or damage of (pitting) the given gear cog, or the guide “latch” responsible for sliding to the given gear. This failure is often due to a low oil level or its poor lubricating properties.
 

 Transmission rebuild cost
Figure 6.  Marked area indicates a possible cause of difficult shifting – damaged 4 gear cog.

 

4. GEARBOX REPAIR – WHAT IS INVOLVED?


Gearbox repair is complicated and may vary significantly for each gearbox (due to different engineering solutions utilized by manufacturers). That is why this guide will not focus on this process (there is further information in the car owner’s manual).

Repair of the gearbox includes the following activities:

  1. Identification of faulty gearbox components on the basis of shifting and gearbox operation.
  2. Removal of the gearbox.
  3. Disassembly of the gearbox (required for the repair).
  4. Determination of particular component wear.
  5. Replacement of damaged and non-repairable parts, or their regeneration.
  6. Assembly of all the components using new gaskets and sealing.
  7. Installation of the gearbox on the vehicle and filling it with fresh oil.

 

 how much to rebuild a transmission
Figure 7.  Disassembled gearbox for inspection and dismantling.

 

In general, all of the worn parts of the gearbox shall be replaced.  This refers primarily to synchronizers and bearings. During repair, it is recommended that you consider the replacement of all bearings.  It does not significantly increase  the total repair costs (usually disassembly, repair and installation of the gearbox account for the majority of the costs).

Gear cogs, differential gears, gearbox bodies, selector forks or shafts (driven and driving ones)  also sometime require repair.

If the gearbox has been disassembled, it is recommended to also replace the gearbox sealing, as a half-shaft seal or jackshaft seal.


5. GEARBOX REPAIR – A GARAGE OR DIY?

As with any car repair, you may always choose the DIY method, provided that you possess the required skills and know-how.

If you do not have required skills, knowledge and necessary tools or devices, the best option will be to have the repairs made in the repair shop. Transmission mechanisms have been precisely synchronized.  Therefore, unskilful handling (any error during assembly) may result in serious gearbox damage.

 Transmission problems
Figure 8.  Gearbox repair is very complicated and should be carried out by a mechanic with the required expertise and experience

 

That is why it is recommended to visit the repair shop to have any repairs and adjustments made by professionals.

It is worthwhile to find a repair shop or professional with expertise and experience in this field. Some websites and social networks, as well as references of your acquaintances may be very helpful. The best solution is to have the repair or adjustment made by the authorized service station or the repair shop having expertise for specific car type ( such as repairs of Japanese or BMW cars only).

This approach ensures professional repairs and prevents any extra unplanned expenditures resulting from services performed by incompetent and inexperienced mechanics. Some service stations have the required spare parts available in stock.  This allows the repairs to be made relatively quickly and saves you time and trouble.

There still are some maintenance operations that you can perform on your own,  such as checking the gearbox oil level and refilling it, if necessary. If you have the required facilities for these maintenance operations available,  for manual transmissions, you can change the oil on your own. It is actually very simple to change the gearbox oil for those who do not have any expertise in this field, if it is done with care and precision. It is essential to fill the gearbox with the recommended oil (preferably a new and synthetic one).

 

6. REPAIR COSTS

Total repair costs depend on the following factors:
1. Repair method and supplier.
2. Spare parts and consumable type.
3. Type, model and age of the car.
4. Repair scope.

The costs will actually be higher for repairs made by  an authorized service station, which will charge you on the basis of its pricelist. That is why it is worthwhile to do some searching to find an independent repair shop that has expertise in gearbox repair in the given car brand.  The cost for the service, including disassembly, repair and assembly (excluding spare parts)  is between 350 PLN and 1500 PLN – depending on labour and the service supplier.

Spare parts also significantly affect the total repair costs.  You will usually be consulted by the service supplier on the choice of spare parts (cheap or expensive ones). If the repair is necessary, it is worth spending more  in order to be sure of the final results.   Since gearbox repairs result in a significant expenditure, it is recommended to use exclusively original spare parts that are more expensive than substitutes.  The substitution of unknown origin spare parts may later result in significant unplanned expenditures.

 We will now analyse the costs that are related to gearbox repair.

The younger and more expensive the car is, the greater the need for the gearbox repair.

For example, if you choose gearbox repair for a 20 year old Alfa Romeo, with 350 thousand km, gearbox repair will cost as much as or will exceed the value of the car.
essential to fill the gearbox with the recommended oil (preferably a new and synthetic one).

transmission repair cost
 
Figure 9.  Gearbox repair may require several spare parts, including  synchronizers, bearings and selector forks.

 

What is the cost of gearbox repair?
Repair costs depend on many factors,  such as car make, model, engine type, spare parts and service supplier, as well as the scope of the repair.

 As an example, we will analyse the costs for a 2003 Honda Civic with an odometer reading of around 180 thousand km.

Gearbox repair - Honda Civic 2003.

Service, including disassembly, repair and assembly    – approximately 400 GBP (an independent repair shop) and approximately 800 GBP (authorised service station)
Gearbox bearings set, original parts ( approximately 200 GBP)
Synchronizers – two gear with slides ( approximately 150 GBP)
Oil, gaskets, half-shaft seal (approximately 70 GBP)

Repair costs will be much higher in the case of a seriously damaged gearbox (damaged cogs, differential gear, broken housing or gear cog) and may be unprofitable, in terms of economy and practice.

 

7. ARE THERE ANY ALTERNATIVE SOLUTIONS?


1.    Replacing the gearbox with a second-hand one

Due to the high cost of gearbox repair, it is worthwhile to consider alternative solutions.

You may also consider the purchase of a second-hand gearbox for the  replacement of your worn one. Although it may be cheaper,  this alternative have some disadvantages. You will be able to assess performance of the gearbox,  and not its assembly.

Before purchasing a second-hand gearbox, drain some gearbox oil to analyze its colour and density. If any metal filling is present, the purchase of this gearbox may not be a good idea. It should be noted that an emptied gearbox or a low oil level may indicate potentially rusty internal parts.

You may also consider the purchase of a regenerated assembly.  Some suppliers may allow you to return the old and faulty assembly in exchange for a more attractive price.  For example, the regenerated gearbox of a VW Golf 1.9 Sdi IV costs around 400 GBP. You still have to pay for the gearbox replacement,  which costs between 200 GBP  and 400 GBP.

The purchased gearbox shall have the same marking as the old one removed from the car. Gearboxes assembled in a few models (e.g. Seat Leon 1.9 TDI and Seat Leon 1.8 T) can have different gearbox ratios. That is why it is worth consulting the vendor regarding the sale terms and conditions as well as the guarantee ( preferably a three month guaran


2.    Application of  Ceramizer® - oil additive

In the case of gearbox medium wear, it is recommended to apply the additive that prevents regeneration, namely Ceramizer®.

This preparation facilitates the restoration and rebuilding of worn synchronizers (that are most often the reason for the grinding noise during shifting or difficult shifting). The application of Ceramizer®  made for gearboxes improves shifting, provides quiet operation and can extend the service life of assemblies as much as five times.

This process does not actually happen immediately.  This is because the ceramic coating is generated (the bonding of additive particles and metal particles is created) due to the high temperature of surfaces subjected to friction due to the action of the Ceramizer® additive immediately after driving at least 1500 km. This preparation also regenerates engine parts and res

 transmission additive
Figure 10.  Ceramizer® transmission additive– improves the operation of the gearbox ( such as worn synchronizers), provides regeneration and extends its service life as much as five times.

 

The ceramic-metal coating that is used protects the gearbox against further wear. This tough, durable and strong coating features a low friction ratio, perfectly transfers heat and is resistant to high temperatures/mechanic load. 

 best transmission additive treatment
Figure  11.  Ceramic coating generated by Ceramizer® additive immediately after driving at least 1500 km. 

Additive costs are very low compared to the costs of gearbox repair. Affordable Ceramizer® does not have any negative impacts and its application may improve gearbox and engine operation that has been confirmed by many of our clients (Read our clients opinions –over 140  pages – click here).


The application of Ceramizer® may not bring positive results,  if there is a failure (e.g. broken cog) or excessive gearbox wear. This kind of failure requires disassembly and repair.


8. PREVENTATIVE MAINTENANCE

It is possible to prevent costly gearbox repair by following 9 maintenance tips that enable you to EXTEND GEARBOX LIFE:

1. Change the gearbox oil as often as recommended in your owner's manual, preferably every 60 thousand km.
2. Do not shift the transmission violently and quickly, since the synchronizer fails to synchronize the shaft and cog rotation.
3. Switch the clutch off completely when shifting, by pressing the clutch pedal to the end.
4. Do not keep hands on the gear lever,  since the selector fork of the cogs may have contact with rotating parts and result in their premature wear.
5. Regularly check your parking space for leaks every 5 thousand km and examine the gearbox for any oil stains.
6. After shifting, release the clutch pedal slowly and evenly ( especially when in 1 and in reverse gear) in order to avoid jerking and violent starting.
7. Never shift into the reverse and first gear, until the car comes to a complete stop.
8. Always shift in the gear that is appropriate to the engine RPM. Remember to watch the revolution counter and consult the manufacturer guidelines on economic driving tips (check your owner’s manual – or consult the dealer).
9. Apply Ceramizer®, a preparation which provides for the preventative maintenance of the gearbox. A gearbox oil additive not only improves performance and prevents grinding noise during shifting,  it also ensures quiet operation and extends assembly life. This saves you money and provides for the regeneration of surfaces that are subjected to friction during gearbox operation.

Visit: www.ceramizer.com to find out more about Ceramizer® preparation.