To diagnose a transmission problem, check fluid levels and inspect the transmission for leaks. Low fluid levels may result in sluggish shifting and may cause permanent damage over time. Inspect automatic transmission filters to ensure they are not clogged or in need of replacement.
Grinding or shaking emitting from the transmission suggests a problem with the gears. Grinding noises are more common with manual transmissions, and noises that occur after engaging the clutch and shifting gears may indicate that the clutch is in need of adjustment or may be overdue for a replacement. Other issues that may cause grinding noises include damaged or worn gear synchronizers. Automatic transmissions tend to shake or jerk rather than grind and may need to be disassembled in order to locate the source of the problem.
Burning smells coming from a vehicle may indicate overheated transmission fluid. Transmission fluid must be kept cool to properly lubricate transmission components, and systems that run too hot can result in increased friction and premature wear. Low fluid levels or using a type of transmission fluid that is unsuitable for a vehicle are both common causes of overheating. Inspect the clutch linkage or shift cables for transmissions that refuse to shift gears.