I have an 03 with a 6 speed. Like others, I've had problems with the gears grinding when shifting, particularly into 2nd and 3rd gears. I tried Red Line gear oil and it was worse, so I went back to regular gear lube. Over several months, it got to be so annoying that I finally took it to the dealer, expecting to need a new transmission. Their mechanic, who related that he owns 2 Miatas (autocrossing one) said that they had many complaints like mine since the 6 speed came out and that, in his experience, the 6 speed would never shift as smoothly as the 5 speed. His disapproval, though unspoken, was obvious. After a test drive, he recommended draining the dino oil and putting in ATF! After being reassured about durability and the warranty, I said OK.
What a difference! It is like having a new transmission. Each gear "snicks" into place without having to pause in neutral to avoid gear clashing. 2nd gear is still a little "nothcier" than the others, but I'm back to having fun with my car. I'm still hesitant about durability and am keeping the invoice, but overall, I am pleased.
Has anyone else heard of anything like this? Is this the equivalent of using Red Line MTL (vs gear lube)?
Randy