amsoil trans fluid?
Melting Slicks
Joined: Apr 2009
Posts: 2,479
Likes: 36
Your 6-speed tranny is designed to use Dexron III ATF. So, yes you are supposed to use automatic tranny fluid. Using anything else is at your own risk. However, there are several members who use other alternatives with good results.
Instructor
Joined: Aug 2012
Posts: 122
Likes: 1
I use Amsoil in the trans on my daily driver, it is awesome stuff. I did extensive research on their products before buying, and from what I read they are the bar none best manufacturer of oils, period. I really want to use Amsoil products in the trans and diff on my C5, however I hear that the 1997-2000 six speeds used paper blocker rings and are prone to failure if you do not use the correct fluid. With that being said, I'm hesitant to switch at the moment until I look into it more. To the OP, you might want to consider this too if your car is a 1997-2000.
Drifting
Joined: Jul 2011
Posts: 1,509
Likes: 10
From: Bay Point California
I don't think you would want to put a quart of additive in your trans. That is a lot. We're usually talking ounces of this stuff. The people that produce the trans fluid you use are not going to back their product if you go and pour a quart of somebody elses stuff in with their stuff. If you buy quality products you don't need these things Sorry to run off at the mouth again but I can't help it.
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Drifting
Joined: Mar 2011
Posts: 1,807
Likes: 331
From: Ocala FL
Some other members on here highly recommend that same fluid for the later model year manuals. I too have an earlier model, '99, so I've been just topping off with the "recommended" stuff every oil change since I have a slow drip/weep with my trans. Eventually I'm going to have to drop the trannie and replace the gaskets but I'm putting it off for as long as I can.
Race Director
Joined: Mar 2003
Posts: 10,789
Likes: 894
From: Northern Illinois
Oldtimer
I've used Amsoil products in my '98 and daily driver for several years. I replaced the transmission and differential fluid in my car before I put it away for the winter last October. You do have to put an additive in the differential, but not the transmission. 
Drifting
Joined: Oct 2010
Posts: 1,873
Likes: 134
From: Bushkill Twp. PA
St. Jude Donor '17
I recently replaced my trans fluid with the Amsoil Torque Drive because I just bought this car and am planning a couple track days this summer. I seem to be in the minority, however my transmission is notchier and chunkier shifting than it was with the stock fluid. I think in the near future I will change it out for something else. My car is a 17k mile Z06, 2002.