Should you have your transmission flushed or just change the fluid & filter?First always change the filter.If you have under a 100K on your vehicle and have never done any heavy towing and the fluid looks not great but OK then it is a toss up fluid and filter is slightly cheaper.If the fluid looks bad or you have towed then flush it and replace the filter.Over a 100K and never touched the trans then only change the filter and fluid the particles in the fluid may be all that is keeping it working if the fluid looks really burnt then you have to chance a flush but you dont need to use a machine. remove the return hose to the cooling system and pump out the fluid replace the hose change the filter and refill messy but cheaper Also I recommend adding Lube Gard after any trans service