Here is some background information from the most recent GM DealerWorld on-line order guide that includes the 2006 GTO.
Quote:
Pontiac GTO
MANUAL TRANSMISSION SPECIFICATIONS
Transmission model: MANUAL 6 -SPEED w/OVERDRIVE TremecT56
RPO Code MN6
GEAR RATIOS
First 2.66
Second 1.78
Third 1.30
Fourth 1.00
Fifth 0.74
Sixth 0.50
Reverse 2.90
TORQUE CONVERTER
Maximum Engine Torque (lb-ft/N-m) 385/519.75
LUBRICANT CAPACITY (pints/litre)
Fluid Capacity 4/1.8928
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INFORMATION POSTED ON SITE
Any GM Solstice Service Manual and Service Bulletin information found here on site, or Sales and Product information should be thought of as correct and accurate as of the date posted. After that any information or procedure should be confirmed as still correct with your dealership.