Just wondering where the gearbox filter is located on a 2000 Honda Accord Coupe 3.0l V6?
The gears do not change very smoothly when engine cold, get a bit better when warmed up, any ideas?

 

The filter is inside the transmission. The only way to change that is to split the case open.

 

Not really sure about your gearbox/trasmission.. but to avoid having to open up the entire trans, I just added an inline magnetic filter to the transmission cooler line coming from the radiator..

Definitely much more effective and much easier to service..
Search for a product called magnefine 3/8"

 

A fluid change should help too. Although it sounds like you might have done that.