The 4L60E automatic transmission in the 2003 5.3L V8 Silverado uses 5.0 quarts of fluid for the initial full, or 11.0 quarts with a total fill.
Use Dexron VI ATF fluid from GM. GM recommends using Dexron VI for all transmission services/top offs/flushes in all Dexron III applications. Dexron VI is backwards compatible with Dexron III, however Dexron III is not forwards compatible with Dexron VI.
The 4L60E transmission was the electronic transmission that replaced the GM Turbo Hydromatic 700R4 transmission. It fully replaced the 700R4 in 1993 for trucks, SUV's and vans and in 1994 for rear wheel passenger cars as well. The TH 700R4 transmission was renamed the 4L60 and by 1992, it became electronically controlled with a Vehicle Speed Sensor, or VSS, and was renamed the 4L60E model.
In recent news, the 2014 Silverado goes on sale in June of 2013. To do more work with less fuel, GM trimmed weight, using more aluminum. With the 2014 Silverado, the new base 4.3 liter V6 and optional 5.3 liter V8 engines are dramatically updated from the engines of the same displacement they replace, with an aluminum block and cylinder heads. The engines will run on E85. It will also come with a column-mounted gearshift and a six-speed automatic transmission.