A manual transmission can be quite sturdy if operated and maintained properly. This is one component that should last the life of the vehicle without any major breakdowns.
Although modern units with cases made from aluminum are not as strong as the “Rock Crushers” that Chevy put out in the late 60’s they are less then half the weight.
This of course increases fuel economy by reducing weight. But also can reduce the tolerance of being run low on fluid. Case damage on a newer trans will usually call for replacement.
These modern day manual units are designed so the internal working parts will operate in a bath of oil circulated by the motion of the gears and the shafts inside.
Some of these units will use oil slinging technology to through oil were it is needed most. This is similar to splash lubrication used in modern automotive engines.
Some manufacturers use a pump and tubes to circulate oil to critical areas that require more lubrication than the natural circulation would offer.
Manual transmission fluids
Providing good internal lubrication is the key to the longevity of the transmissions life. If the amount of lubrication falls below the minimum levels or if the trans fluid becomes too dirty major problems can result.
Note that most car makers do not offer fluid filtering on a manual trans. But instead may have magnets inside to pull metal shavings out of the fluid. These magnets can aid in trouble diagnosis as they will hold the worn material for inspection. I have more information about the insides and how to learn manual transmissions.
Different car manufacturers will often use different transmission fluids in their units. The internal assembly procedure and tolerances are specifically designed to operate with this specific fluid installed from the factory.
Installing the wrong kind of manual transmission lubricant can affect the overall protection of the internal moving parts.
An example would be if the transaxle were designed to use automatic transmission fluid. If 75W90 gear oil is installed in replacement of the transmission fluid, inadequate lubrication is most often the result.
Manual transmission service
Prior to beginning any service or repair work, be sure, you know exactly which transmission you will be working on. This will ensure that you are following the correct procedures and specifications.
Sometimes proper identification of the manual trans-axle can be difficult. Application model numbers can be contained within part number codes.
The overall external appearance of the unit cannot be used for sole identification purposes as in the old days. Several model transmissions may share external housing configurations on newer cars.
In most cases, manual transmission identification numbers are found stamped on the case or on a metal tag held by a housing bolt.
If you find this service tag you can use your online car service manual to decipher the identification numbers.
Most ID numbers include the model, gear ratios, assembly date, and the manufacturer of the unit.
Whenever you work with a transmission with a metal ID tag make sure the tag is put back on the transmission so the next auto mechanic will be able to identify the transmission properly.
If the transmission does not have an ID tag at all comparing it with those in the vehicle service manual can often identify it.
Also your local dealership may be able to help you by identifying the RPO code, which is located on a factory-installed tag. The location of your RPO code tag can be obtained from the manufacturers dealership network.
Overhauling manual transmissions is not as popular as it once was. Also finding a repair center that specializes in performing the service is also becoming harder to locate.
In many cases, special tools will be required to remove and install shafts and gears. In the inverse some will require no special tools and are easier to re manufacture. Practicing by purchasing junk yard units and tearing them down is also highly recommended.
Another benefit is you can sell these completed rebuilt manual transmissions on either e-bay, craigs list or other internet portals. You can even specialize in specific sport models and become the go to guy for this vital component. You can build a monster motor but you need to apply that power to the street.
Learning about how a manual transmission works would be considered a valuable skill in almost any repair shop environment. Becoming certified in manual drive trains can push even new auto mechanics to the front of the line when its time to hire.