A slipping transmission is frequently caused by a problem with the vehicle's transmission fluid. Additionally, important components of the transmission, particularly the bands, may be worn or broken. Transmission slippage can also be instigated by clutch malfunction in both automatic and standard vehicles.
There are a number of fluid-related problems that can induce transmission slippage. For example, fluid levels in the vehicle may be too low, or even burnt. To diagnose the latter, one should check if the fluid has the smell of burnt toast, or is blackish in color. One should also check to see for leaking transmission fluid, as this can be the root of the difficulty.
If bands are the issue, it may simply be a case of switching out the old product with new ones or having them readjusted. However, the problem could also extend to the transmission gears themselves, which may be worn and not linking properly during operation. With manual transmissions, clutch problems are the cause of slippage approximately 90 percent of the time, as they are usually thinned out from use.
Additional possibilities include the solenoid or torque converter. It may be that damage or an electrical problem has caused the solenoid to release incorrect fluid levels into the transmission. Similarly, the torque converter may be affecting fluid flow, thus causing the transmission to misbehave; slippage is a common symptom.