Might seem like an obvious question, but this is an argument older than the internet. I acquired a new, fancy beater that may have never had its transmission serviced. Fluid is mostly brown, trans doesn't slip, but does shift a little harder than it should. Due to the horror stories of people flushing their very dirty fluid and replacing it with new, only to have their trans fail quickly, I wanted to ask you guys your opinion. Let it rip.

 

If you're gonna put crappy ATF in it, don't do it.

If you're gonna put Amsoil in it, then change it.

P.S., don't forget to install a magnefine filter

 

I would change it and do the recommended flush procedure. I used Valvoline import fluid and then OEM Honda fluid for mine. Works just fine after 18k miles. When I got the car it was manually shifted between two gears.

I think RonJ has mentioned the Castrol Import stuff works well too.

OP- post your year and engine in the original post as well. Required for tech threads.

 

Op missing info.

 

Three consecutive ATF drain-refill cycles. Between each drain-refill cycle, slowly shift through all gears several times with the engine running.