Amsoil ATD here as well.
[Z06] Manual Trans Oil
Le Mans Master
Joined: May 2005
Posts: 6,366
Likes: 249
From: Fort Lauderdale, Florida
Royal Purple Synchromax. It's an oil made specifically for manual trans cars that specify ATF. I've tried several oils in my quest to get smoother shifting and this oil has been the best.
Dogface
Joined: Jul 2004
Posts: 25,974
Likes: 120
From: At the Beach, FL
St. Jude Donor '15, '17
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Melting Slicks
Joined: Oct 2001
Posts: 2,786
Likes: 22
From: Cary NC
I also use their oil, ps fluid, and diff fluid. No complaints.
My little Celica commuter car has 2 bad synchros. I just drained it and put the RP in there too. Doesn't fix them for sure but makes them easier to deal with.
Race Director
Joined: Jul 2007
Posts: 10,961
Likes: 2,643
From: Texas Hill Country
4 quarts. Drivers side there is the fill hole. Disconnect the electrical plug and unscrew. next, unscrew the drain plug. after it drains, redo the plug and fill with fluid until it starts seeping/flowing out of fill hole. redo fill plug, replug electrical plug and go. you will need a fluid pump (the kind that fits into the bottle and pumps fluid up because there is no room to pour down into the trans.
Pro
Joined: Nov 2005
Posts: 597
Likes: 10
From: MO
trans oil
I have an '02 with 14000 miles, just changed the fluid to Royal Purple Syncromax. Before the change it was somewhat "notchy" and would only go into reverse with some additional pressure. Reminded me of my John Deere. Now it shifts smoothly with much less effort. I bought the RP at the local speed shop for $8 per quart. Took a little over 3 quarts. Be ready when you take the drain plug out to drain your transmission, the fluid is thin and comes out fast. 
Race Director
Joined: Jul 2007
Posts: 10,961
Likes: 2,643
From: Texas Hill Country
Melting Slicks
Joined: Jan 2007
Posts: 3,107
Likes: 7
From: Sandy Ego Ca.