Why Does My Automatic Car Shift Hard?

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Hard shifting in an automatic vehicle is typically the result of a faulty or failing transmission. An automatic transmission is comprised of gears, fluid, bell housing and a filter. Problems arising in any of these areas can result in hard or clunky shifting. The most common reasons for hard shifting in automatic vehicles are incorrect fluid levels, transmission leaks, clogged filters or a complete system failure.

It is crucial to check the vehicle’s transmission fluid at least twice a year. Low fluid levels can result in hard shifting that eventually leads to transmission damage. Check for leaks at the filter tube base, speed sensor mounting point, between the engine and the transmission, and at the selector shaft if fluid levels are low or a leak is noticed.

Low fluid levels in the transmission typically stem from leaks. Leaks occur most commonly in the input or output shafts on the transmission. These moving parts possess rubber seals that wear or break over time. Worn seals lead to hard shifting by causing the input and output shafts to stall. A transmission sealer provides a suitable fix to restore the seals and improve shifting.

Transmission fluid is also susceptible to contamination. If the transmission overheats, the fluid oxidizes and fails to lubricate and cool the transaxle’s components. Old, dirty and oxidized transmission fluid cause the same symptoms of low or leaking transmission fluid and filter clogs. The filter is also vital to the transmission’s performance. Clogged filters do not properly expel dirt, grime or other pollutants that can cause hard shifting.