Diagnosing: Transmission Shudder vs. Engine Performance

– Diagnosing a Shudder – Diagnosing a Shudder can be a bit tricky at times and can be often be caused by different problems, namely: Engine Misfire, An Engine Performance Problem, A Calibration issue with the computer, a slipping clutch or a Torque Converter Condition. First and foremost the diagnosis should start by checking the computer system for engine performance or gearbox-related trouble codes. One should always first repair all engine related troubles codes before attempting to diagnose a transmission shudder as the transmission computer receives all of its calculating variables from the engine computer. The easiest way to diagnose whether the transmission is causing a shudder is to monitor the TCC Slip with your diagnostic scanning computer. If the TCC Slip increases during the shudder, it is most likely that the shudder is coming from your transmission. If the TCC Slip doesn’t increase during the shudder, it is most likely that your shudder isn’t related to the transmission and may be caused by an engine performance problem.

– Transmission shudder – The clutch component or TCC slipping is usually the cause of a Transmission Shudder. This is caused by a low pressure in the clutch circuit or a worn clutch. One should monitor the TCC Slip in order to determine if the shudder is transmission related.

– Engine Performance Shudder – Most commonly, a non-transmission related condition that could cause a shudder are: Engine Misfires, Engine Performance Problems or computer calibration issues. Engine misfires being the most common cause. Engine performance problems can and will interfere with transmission operation. Specific load input faults, namely, mass air flow (MAF), Manifold absolute pressure (MAP), Throttle Position Sensor (TPS) and Intake air temperature (IAT) can cause problems with line rise and TCC duty cycle. All engine performance system needs to repaired before trying to diagnose a transmission shudder.

– Computer Programming – Manufacturers today offer computer programming updates to correct engine performance and transmission related problems. Always update the software prior to attempting to diagnose a shudder problem.

The CRS Gearbox (Controlled Rotation System)

A group of Dutch inventors has developed a gearbox they say could revolutionize the automotive and bike industries. Developed by Parts Services Holland and called the Controlled Rotation System (CRS), it does away with one of the main components of a gearbox–the gears themselves. However, the team says it cannot be compared with existing continuously variable transmission (CVT) designs.

A CVT works on the principle of two cone-shaped pulleys and a V-belt. As the belt is moved up or down one of the pulleys, the gear ratio changes–hence the name “continuously variable transmission”. No gears are changed, no steps between ratios are required. The CRS is similar to a CVT in that it uses a belt mounted on two discs, but the operation is different. Here, a digitally-operated hydraulic pump increases or decreases the diameter of the discs, the difference between the two changing the transmission ratio.

The system was originally developed for bicycles, to eradicate the issue of chains jumping off the gear teeth during changes. The video above demonstrates the principle–a large-diameter rear sprocket (or disc, in this case) means a low ratio; the smaller the sprocket (/disc), the higher the ratio, used at higher speeds.

The team of four then developed the bicycle system into a prototype for cars. Interestingly, they say it could work best with electric vehicles, as the electric motor could run at a constant rpm with the gearing adjusted to suit. With electric cars becoming more prevalent, it could well be a system we’ll see appearing in future road vehicles.

Manual vs Automatic Gearboxes

Mechanically speaking, when comparing an Automatic Transmission with a Manual Transmission their concepts and purposes is very similar. An engine is limited to producing a “drive” from 0 rpm to approximately 7000 rpm (this may vary from car to car). In order for a vehicle to achieve higher speeds a gearbox is required in order to change the engine’s output into different ratios/speeds. The gearbox must therefore have an input (equal to the engine output speed) and an output (varies according to the selected gear).

Continue reading “Manual vs Automatic Gearboxes”

Audi’s DSG Gearbox

Audi’s DIRECT SHIFT GEARBOX or also known as the DSG is controlled electronically with its dual clutch and multiple shafts it has not clutch pedal and is full automatic with semi manual control. In basic terms this gearbox contains 2 manual gearboxes in 1 casing. This allows the gearbox to have much quicker shifts and due to the fact that it has a dual clutch system, there is no use for a torque converter which is found in the conventional automatic gearbox.
How does it shift quicker? – As explained previously, the DSG gearbox has multiple shafts (2 manual gearboxes in 1 casing)… The gearbox will pre-select the next gear and the previous gear so that the gear is preloaded to take the next/previous gear and release the current gear simultaneously.

Audi’s CVT Gearbox

Audi’s CONTINUOSLY VARIABLE TRANSMISSION or also known as the CVT or Multitronic is controlled electronically giving the driver a stepless automatic transmission. Still working with a torque converter this gearbox can continuously vary the ratio between the input shaft and output shaft, providing an infinite number of gear ratios. It is chain driven allowing the gear ratio’s to grow or shrink as you drive giving you either fuel efficiency or maximum performance, depending on the drivers inputs, driving conditions and engine load.

Gearbox Do’s and Don’ts

Maintaining your transmission is just as important as getting your regular engine oil changes. Below are a few standard tips to help you avoid future transmission damage:

  • Do scheduled maintenance according to vehicle owner’s manual.
    Do have transmission fluid checked when having oil changed.
    Do not drive a vehicle with low or no transmission fluid.
    Do not change gear ranges from drive to reverse when your vehicle is moving.
    Do not spin tires on turns with front wheel drive vehicle’s.
    Do not drive your vehicle when there are transmission problems, this may cause further damage.
    Do not drag race your vehicle as it puts unnecessary strain on your transmission.
    Do not drive in 4×4 range on dry pavement unless vehicle is all wheel or automatic 4×4.
    Do make sure you come to a complete stop before moving gear into another range.
    Do not drive on spare tires or mismatched tire sizes with front wheel or all wheel drive vehicles for extended periods of time.

Automatic Gearbox Maintenance

Maintenance

Transmission fluid should be changed periodically.  Your owner’s manual should give you the recommended intervals which could be anywhere from 15,000 miles to 100,000 miles.  Most transmission experts recommend changing the fluid and filter  every 25,000 miles.

Few transmissions have drain plugs to drain the old fluid.  In order to get the fluid out, the technician removes the transmission oil pan.  This is quite a messy job and generally not recommended for the casual do-it-yourself er.  Even if the transmission has a drain plug, the only way to also change the transmission filter is to remove the pan. When the pan is down, the technician can check for metal shavings and other debris which are indicators of impending transmission problems.

In most cases during these transmission services, only about half the oil is able to be removed from the unit. This is because much of the oil is in the torque converter and cooler lines and cannot be drained without major disassembly.  The fluid change intervals are based on the fact that some old fluid remains in the system.

When the transmission is serviced, make sure that the correct fluid is used to re-fill it.  Each transmission manufacturer has their own recommendation for the proper fluid to use and the internal components are designed for that specific formula.   A transmission will not work properly or may even slip or shudder with the incorrect fluid, so make sure that you double check.  Your owner’s manual will tell you which fluid is required.  Naturally, the owner’s manual will try to convince you to only use the manufacturer’s branded fluid, but they will also provide you with the specs for the oil.  If the aftermarket product indicates on its container that they meet or exceed the specs for a particular type of transmission fluid, it is generally ok to use that product.