Last year, the 6l80 transmission failed, prompting a complete overhaul with billet parts from Circle D transmissions, capable of handling up to 1000hp. Despite currently running at 701hp to the wheels, I took it for tuning after adding a 3200 converter, assuming it needed tuning I took it to the tuner. They set transmission to relearning, and I didn't think much of it at the time since they had tuned it before. However, the gas mileage has significantly worsened, now at 27L per 100kms (8.7mpg). After investing nearly $10k in the rebuild, I'm eager to ensure it's properly tuned, as I understand that a faulty tune alone can lead to transmission failure.
If anyone has any insight or knowledge that would be awesome.
