TegTypeR:Having owned a V8 with the same gearbox (all be it with a fair bit less power), I wondered then as I do now why they haven't refined it yet?
From the GM Performance website...
Enhanced TR6060 Transmission
Another factor in the performance and durability of the ZR1 drivetrain is of course the transmission, which is an evolved version of the T56 we know and love. "The TR6060 launched with the 2008 model year, and that was just one more step in taking a transmission that 10 years ago was capable of 350 lb-ft and getting it up into the torque ranges of today," says Kline. Features like increased gear widths and a new synchronizer package all carry over into the 2009 ZR1, but the new car also gets high-strength materials, like an SAE 9310 input shaft and SAE 4615 mainshaft.
Additionally, fifth and sixth gear now sport higher-strength SAE 8822 material. Surely one of the reasons for this is that they'll be used to their full ability. Thanks to its application-specific close-ratio gearset, the ZR1 will make better use of its overdrive ratios and will actually top out in top gear--a first for six-speed Corvettes. Rpm drop during gear changes will be minimized--and first gear (by carrying a taller 2.29 ratio) also allows better traction at low speed, including during a launch. Other slight changes, like alterations to the gear helix angles were made for the ZR1, but despite all of its strength-enhancing features, GM says there's no driver-perceptible difference between this car's tranny and the other TR6060s in the lineup. "It's a very nice performance package, with the same type of no-noise operation that you expect out of the Tremec products--but with the strength to handle the torque of the LS9," says Kline.
The TR6060 Transmission is an improved version of the T-56 which was also used in the following cars...
Aston Martin DB7 Vantage, 1999–2003
Aston Martin V12 Vanquish, 2001–2006
I guess Aston didn't know what they were doing either.
Another test with slightly different results.
"The pump dont work cause the vandals took the handles." (Robert Allen Zimmerman)