Generally speaking, a transmission flush should be performed every 30, 000 miles or about every 2 years.  Yet, sometimes, a transmission flush is required much sooner.  Below is a list of signs you may need to get your transmission fluid changed before that 30, 000 miles or that 2 years.

⦁    Your transmission is grinding or making strange noises.  These two things could mean you have contaminated your fluid with dirt, grease or sludge.  Check your transmission fluid level when the car is running.  The transmission fluid should be bright red.  If it is brown or black, you need your transmission fluid changed.

⦁    You have problems shifting gears.  Contaminated transmission fluid can cause your vehicle to become sluggish in shifting gears.  A manual vehicle will find it very difficult to change gears at all. 

⦁    You find your gears slipping.  Contaminated transmission fluid will cause a lack of hydraulic power, restricting its ability to keep you in the appropriate gear.

⦁    Your vehicle surges forward or falls backwards.  Contaminated transmission fluid creates an inconsistent flow of clean transmission fluid that is required for smooth operation.  This contaminated transmission fluid will cause your vehicle to jump forward or fall backwards for no reason.

⦁    Your vehicle stalls for a few seconds.  If you find your vehicle stalls for a moment after you have put it in gear, your transmission fluid may be contaminated and me need to be changed.





Source:
Cars Direct (May 29, 2013).  5 Signs That Your Car Needs a Transmission Flush.  Retrieved from http://www.carsdirect.com/car-repair/5-most-common-signs-that-your-car-needs-a-transmission-flush