I read the deeper pan from the CTS prevents flares.
Parts Info:
2 Gallons AC Delco Dexron VI Automatic Transmission Fluid
AC Delco Part Number: 10-9030
GM Part Number: 88861954
$23.64 a gallon thru Amazon.com - Free Shipping
Transmission Filter from the Cadillac CTS and Many Trucks (Wide mouth)
GM / AC Delco Part Number: 24236933
$28.79 thru RockAuto.com - Bit Cheaper on Amazon.com
Transmission Pan from the Camaro/Cadillac STS (Deep Pan)
GM / AC Delco Part Number: 24250062
$22.79 thru RockAuto.com - Best price I found
Transmission Pan Gasket (can reuse old one if not to many miles on it)
GM / AC Delco Part Number: 24224781
$12.00 Thru RockAuto.com - Only $6.00 shipping for 3 items.
Info:
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Explination from Car Modder in case it gets lost, that site is going down piece by piece:
The 6L80 Automatic Transmission fitted to Holden Commodore V8 models (And export versions of this vehicle such as the Pontiac G8, Vauxhall VXR8, and Chevrolet Caprice, Chevrolet SS) features a transmission sump unique to these model vehicles.
The standard Holden fitted sump is a low profile model fitted primarily to allow for greater ground clearance than the usual sump fitted to other models with the 6L80 Transmission such as the Chevrolet Camaro.
Although this increases ground clearance, it also has the undesired effect of reducing the amount of transmission fluid capacity of the transmission.
This has the flow on effect whereby with the reduced transmission fluid level, it is more likely for the transmission to to experience transmission fluid starvation under situations such as harsh braking, acceleration, or high cornering forces.
This fluid starvation will result in transmission gear flaring on gear shifts, slow gear changes, and poor cold temperature performance.
The solution to this is to fit the larger, deeper transmission sump, and the longer (larger mouthed) transmission fluid filter from the Chevrolet Camaro model (That uses the 6L80 6 Speed Automatic Transmission).
This allows for the transmission to hold an extra 2 Litres of transmission fluid, as well as allowing the transmission fluid pick-up to sit lower in the pan. (Reducing the likelihood of transmission fluid starvation when braking, accelerating and cornering.