I just shift whenever I feel I could benefit from having the next gear. Downshifting for me depends on how fast I need to be at a complete stop. My winter car (Beretta), won't downshift all the way to 2 MPH like the RX-8 does.

 

I know that ^ is old post but I LOLd hard

 

I have also noticed that it seems to grind just a bit if you try to shift from 1st - 2nd above 4500 RPMs.. My Porsche 944 would let me wind up the engine out of first and go to second very smoothly, but if I wind up the -8 much above 4000 RPM, the trans wants to grind a bit into gear.. What's up with that?

 

That sounds like a syncro problem, which could be because of fluid choice, fluid age, or actually failing syncros. Also possible that it could be a motor mount problem. It certainly isn't normal.

 

Hmm.. I wonder about the fluid choice.. I don't remember the car being quite so "notchy" with the original Mazda fluid. When I go the car, I swapped the Mazda trans fluid for the Red Line fluid, as most here in the forum recommended. Although it is possible it was the same and I don't remember.. I'd have to swap back to the OEM fluid to check it out.. A minor PITA, but almost worthwhile. The fluid has only a couple thousand miles on it, as I swapped it when I bought the car back in May. I did notice that any gear whine I had disappeared when I switched to the Red Line fluid. If I shift from 1st to 2nd below 4500 RPM, smooth as silk.. between 4500-5000 RPM, I can feel a slight, but definite click into gear.. above 5000 RPM, it's a very slight grind. Seems others here have the same experience?

 

Going back to drive the car with the intention of being more conscious of what the tranny is doing, I see that's it's not really grinding into 2nd, as it is just a more a noticeable "clunk" into 2nd gear in the higher RPM's. Several more forum members have reported the same characteristics in their cars, so I know it's common in the fleet. One member reported the conditions going away after installing Honda's manual tranny fluid in their gearbox.