Me too.
Best T56 fluid?
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
I think you will likely get multiple answers on what's best, I am using Amsoil and it has been shifting fine with it so I don't plan to change anytime soon. Some are running the Redline MTL, I am unsure of how well that works. There is also the question of when the paper blocking rings were replaced and the impact of that change on what oil you can safely use.
Le Mans Master
Joined: Feb 2002
Posts: 6,937
Likes: 21
From: Waldorf MD
Amsoil ATF or ATD works great. I personally now run Amsoil ATD. I previously ran Mobil 1 ATF, after 50,000 miles it was grinding when going into 6th gear, a change to Amsoil ATD stopped that. I am not necessarly blaming Mobil 1, these transmissions are sensitive to dirty oil, I think they need changed every 50,000 miles. And the service manual says you never have to change it !!!
Last edited by Oldvetter; Nov 13, 2007 at 03:43 PM.
Race Director
Joined: Sep 2004
Posts: 17,786
Likes: 4
From: Redsox, Pats, Celts & Bruins !!! Redsox Nation !!!
St. Jude Donor '06-'07-'08-'09-'10-'11-'12
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Safety Car
Joined: Nov 2000
Posts: 4,419
Likes: 6
From: Arroyo Grande CA
According to this: http://corvettemechanic.com/forum/sh...ghlight=dexron Dexron VI is not for the manual tranny.
Former Vendor
Joined: May 2006
Posts: 718
Likes: 1
From: Riviera Beach FL
Your transmission has paper blocker rings unless it has been rebuilt. This limits the brand of transmission fluids you can use. Search C5 tech for "paper blocker rings" for brands that will work.
Le Mans Master
Joined: Jun 2002
Posts: 8,352
Likes: 103
From: In the pit, trying to love someone.
Former Vendor
Joined: May 2003
Posts: 1,313
Likes: 4
From: Livermore CA
I found that in some cases the Redline MTL can be too slick. The D4ATF is better in the long run. Another good fluid is GM's really expensive bottle of syncromesh fluid. They have two versions, the not so cheap version is pretty cool.
Rick
Rick
Melting Slicks
Joined: Sep 2003
Posts: 2,458
Likes: 105
From: Northville Michigan
I just switched from Castrol SynTec LT to Royal Purple Syncromesh.
The Castrol Syntec LT worked fine once it was warmed up. With it I never had a high temperature warning during track days.
The Royal Purple Syncromesh shifts much easier cold.
I have the Carbon Fiber blocker rings.
The Castrol Syntec LT worked fine once it was warmed up. With it I never had a high temperature warning during track days.
The Royal Purple Syncromesh shifts much easier cold.
I have the Carbon Fiber blocker rings.
Racer
Joined: Jan 2006
Posts: 479
Likes: 2
From: Hollywood Maryland
Beware of Ruining the Paper (Celulose) Blockers
After extensive reading on this forum, it looks as if AMSoil Synthetic ATF is the way to go on a '99 MN6. As stated above, you can damage the internal blockers of the T56 by not using the right transmission fluid. I replaced the factory transmission oil with AMSOil Synthetic ATF 11,000 miles ago and have had absolutely no issues and nothing but smooth shifting despite the 'mickey mouse' factory shifter. Be safe, go with AMSOil Synthetic ATF.
