Can a transmission flush be bad?
Correspondingly, does flushing a transmission cause problems?
If you do a flush when there is damaged transmission material in the transmission fluid, you could cause a problem in the valve body at the bottom of the transmission. If the valve body gets gunked up with damaged transmission material, you could lose the ability to shift between gears.
Secondly, are transmission flushes worth it?
Under normal driving conditions, a flush is NOT necessary at 46K miles. The shops make money on flushes, that's why they recommend them. Most transmissions are good for 100,000 miles before requiring maintenance. Maintenance is debated between a flush and a fluid drain and fill.
Where a transmission fluid change will only replace some of the existing fluid for new, clean fluid, a transmission fluid flush completely removes all old fluid and replaces it with new. Mechanics recommend a complete flush approximately every 60,000 miles.