All transmission jobs begin with a thorough diagnostic so as to know what direction to go. Unfortunately most transmission repairs are done with the transmission removed. When that time comes we are more then ready to tackle the project. With over 36 years of building experience alone we are well versed in the proper repair procedures. Transmissions come with a 1 year unlimited mileage warranty.
Incoming transmissions are torn down in the tear down room. Components are cleaned and Moved to the "Clean" room for assembly.
In the clean room new components are pulled from the shelves and the long process of reassembly begins and transmissions are delivered out to shop when complete.
The need for a transmission in an automobile is a consequence of the characteristics of the internal combustion engine. Engines typically operate over a range of 600 to about 7000 rpm (though this varies, and is typically less for diesel engines), while the car's wheels rotate between 0 rpm and around 1800 rpm.
Furthermore, the engine provides its highest torque and power outputs unevenly across the rev range resulting in a torque band and a power band. Often the greatest torque is required when the vehicle is moving from rest or traveling slowly, while maximum power is needed at high speed. Therefore, a system is required that transforms the engine's output so that it can supply high torque at low speeds, but also operate at highway speeds with the motor still operating within its limits. Transmissions perform this transformation.
The dynamics of a car vary with speed: at low speeds, acceleration is limited by the inertia of vehicular gross mass; while at cruising or maximum speeds wind resistance is the dominant barrier.
Many transmissions and gears used in automotive and truck applications are contained in a cast iron case, though more frequently aluminium is used for lower weight especially in cars. There are usually three shafts: a mainshaft, a countershaft, and an idler shaft.
The mainshaft extends outside the case in both directions: the input shaft towards the engine, and the output shaft towards the rear axle (on rear wheel drive cars. Front wheel drives generally have the engine and transmission mounted transversely, the differential being part of the transmission assembly.) The shaft is suspended by the main bearings, and is split towards the input end. At the point of the split, a pilot bearing holds the shafts together. The gears and clutches ride on the mainshaft, the gears being free to turn relative to the mainshaft except when engaged by the clutches.
Manual transmissions come in two basic types:
- A simple but rugged sliding-mesh or unsynchronized/non-synchronous system, where straight-cut spur gear sets spin freely, and must be synchronized by the operator matching engine revs to road speed, to avoid noisy and damaging clashing of the gears
- The now ubiquitous constant-mesh gearboxes, which can include non-synchronised, or synchronized/synchromesh systems, where typically diagonal cut helical (or sometimes either straight-cut, or double-helical) gear sets are constantly "meshed" together, and a dog clutch is used for changing gears. On synchromesh boxes, friction cones or "synchro-rings" are used in addition to the dog clutch to closely match the rotational speeds of the two sides of the (declutched) transmission before making a full mechanical engagement.
The former type was standard in many vintage cars (alongside e.g. epicyclic and multi-clutch systems) before the development of constant-mesh manuals and hydraulic-epicyclic automatics, older heavy-duty trucks, and can still be found in use in some agricultural equipment. The latter is the modern standard for on- and off-road transport manual and semi-automatic transmission, although it may be found in many forms; e.g., non-synchronised straight-cut in racetrack or super-heavy-duty applications, non-synchro helical in the majority of heavy trucks and motorcycles and in certain classic cars (e.g. the Fiat 500), and partly or fully synchronised helical in almost all modern manual-shift passenger cars and light trucks.
Manual transmissions are the most common type outside North America and Australia. They are cheaper, lighter, usually give better performance, but the newest automatic transmissions and CVTs give better fuel economy. It is customary for new drivers to learn, and be tested, on a car with a manual gear change. In Malaysia and Denmark all cars used for testing (and because of that, virtually all those used for instruction as well) have a manual transmission. In Japan, the Philippines, Germany, Poland, Italy, Israel, the Netherlands, Belgium, New Zealand, Austria, Bulgaria, the UK, Ireland, Sweden, Norway, Estonia, France, Spain, Switzerland, the Australian states of Victoria, Western Australia and Queensland, Finland, Latvia, Lithuania and the Czech Republic, a test pass using an automatic car does not entitle the driver to use a manual car on the public road; a test with a manual car is required. Manual transmissions are much more common than automatic transmissions in Asia, Africa, South America and Europe.
Manual transmissions can include both synchronized and unsynchronized gearing. For example, reverse gear is usually unsynchronised, as the driver is only expected to engage it when the vehicle is at a standstill. Many older (up to 1970s) cars also lacked synchronisation on first gear (for various reasons—cost, typically "shorter" overall gearing, engines typically having more low-end torque, the extreme wear on a frequently used first gear synchroniser ...), meaning it also could only be used for moving away from a stop unless the driver became adept at double-declutching and had a particular need to regularly downshift into the lowest gear.
Some manual transmissions have an extremely low ratio for first gear, called a creeper gear or granny gear. Such gears are usually not synchronized. This feature is common on pick-up trucks tailored to trailer-towing, farming, or construction-site work. During normal on-road use, the truck is usually driven without using the creeper gear at all, and second gear is used from a standing start. Some off-road vehicles, most particularly the Willy's Jeep and its descendants, also had transmissions with "granny first's" either as standard or an option, but this function is now more often provided for by a low-range transfer gearbox attached to a normal fully synchronized transmission.
Some commercial applications use non-synchronized manual transmissions that require a skilled operator. Depending on the country, many local, regional, and national laws govern operation of these types of vehicles (see Commercial Driver's License). This class may include commercial, military, agricultural, or engineering vehicles. Some of these may use combinations of types for multi-purpose functions. An example is a power take-off (PTO) gear. The non-synchronous transmission type requires an understanding of gear range, torque, engine power, and multi-functional clutch and shifter functions. Also see Double-clutching, and Clutch-brake sections of the main article. Float shifting is the process of shifting gears without using the clutch.
Most modern North American, and some European and Japanese cars have an automatic transmission that selects an appropriate gear ratio without any operator intervention. They primarily use hydraulics to select gears, depending on pressure exerted by fluid within the transmission assembly. Rather than using a clutch to engage the transmission, a fluid flywheel, or torque converter is placed in between the engine and transmission. It is possible for the driver to control the number of gears in use or select reverse, though precise control of which gear is in use may or may not be possible.
Automatic transmissions are easy to use. However, in the past, some automatic transmissions of this type have had a number of problems; they were complex and expensive, sometimes had reliability problems (which sometimes caused more expenses in repair), have often been less fuel-efficient than their manual counterparts (due to "slippage" in the torque converter), and their shift time was slower than a manual making them uncompetitive for racing. With the advancement of modern automatic transmissions this has changed.
Attempts to improve fuel efficiency of automatic transmissions include the use of torque converters that lock up beyond a certain speed or in higher gear ratios, eliminating power loss, and overdrive gears that automatically actuate above certain speeds. In older transmissions, both technologies could be intrusive, when conditions are such that they repeatedly cut in and out as speed and such load factors as grade or wind vary slightly. Current computerized transmissions possess complex programming that both maximizes fuel efficiency and eliminates intrusiveness. This is due mainly to electronic rather than mechanical advances, though improvements in CVT technology and the use of automatic clutches have also helped. A few cars, including the 2013 Subaru Impreza and the 2012 model of the Honda Jazz sold in the UK, actually claim marginally better fuel consumption for the CVT version than the manual version.
For certain applications, the slippage inherent in automatic transmissions can be advantageous. For instance, in drag racing, the automatic transmission allows the car to stop with the engine at a high rpm (the "stall speed") to allow for a very quick launch when the brakes are released. In fact, a common modification is to increase the stall speed of the transmission. This is even more advantageous for turbocharged engines, where the turbocharger must be kept spinning at high rpm by a large flow of exhaust to maintain the boost pressure and eliminate the turbo lag that occurs when the throttle suddenly opens on an idling engine.
A hybrid form of transmission where an integrated control system handles manipulation of the clutch automatically, but the driver can still—and may be required to—take manual control of gear selection. This is sometimes called a "clutchless manual", or "automated manual" transmission. Many of these transmissions allow the driver to fully delegate gear shifting choice to the control system, which then effectively acts as if it was a regular automatic transmission. They are generally designed using manual transmission "internals", and when used in passenger cars, have synchromesh operated helical constant mesh gear sets.
Early semi-automatic systems used a variety of mechanical and hydraulic systems—including centrifugal clutches, torque converters, electro-mechanical (and even electrostatic) and servo/solenoid controlled clutches—and control schemes—automatic declutching when moving the gearstick, pre-selector controls, centrifugal clutches with drum-sequential shift requiring the driver to lift the throttle for a successful shift, etc.—and some were little more than regular lock-up torque converter automatics with manual gear selection.
Most modern implementations, however, are standard or slightly modified manual transmissions (and very occasionally modified automatics—even including a few cases of CVTs with "fake" fixed gear ratios), with servo-controlled clutching and shifting under command of the central engine computer. These are intended as a combined replacement option both for more expensive and less efficient "normal" automatic systems, and for drivers who prefer manual shift but are no longer able to operate a clutch, and users are encouraged to leave the shift lever in fully automatic "drive" most of the time, only engaging manual-sequential mode for sporty driving or when otherwise strictly necessary.
Specific types of this transmission include: Easytronic, Tiptronic and Geartronic, as well as the systems used as standard in all ICE-powered Smart-MCC vehicles, and on geared step-through scooters such as the Honda Super Cub or Suzuki Address.
A dual-clutch transmission alternately uses two sets of internals, each with its own clutch, so that a "gearchange" actually only consists of one clutch engaging as the other disengages—providing a supposedly "seamless" shift with no break in (or jarring reuptake of) power transmission. Each clutch's attached shaft carries half of the total input gear complement (with a shared output shaft), including synchronised dog clutch systems that pre-select which of its set of ratios is most likely needed at the next shift, under command of a computerised control system. Specific types of this transmission include: Direct-Shift Gearbox.
There are also sequential transmissions that use the rotation of a drum to switch gears, much like those of a typical fully manual motorcycle. These can be designed with a manual or automatic clutch system, and may be found both in automobiles (particularly track and rally racing cars), motorcycles (typically light "step-thru" type city utility bikes, e.g., the Honda Super Cub) and quadbikes (often with a separately engaged reversing gear), the latter two normally using a scooter-style centrifugal clutch.