Tony from Goulburn, Gene, and everyone else. I found a product called "Redex" at my local auto store on the weekend. You can either empty it in the fuel tank or pour it down the carb. I poured it slowly down the carb whilst engine was on fast idle, then quickly until it stalled out. There was a little black smoke but not a great deal. I also changed the oil to 10W 30 (old oil level was fine but very black after 3 months). There were 3 brands to choose from Nulon, Castrol GTX, and Shell Eco. I used Shell. Then left it overnight as Gene suggested. I checked the torque converter and the bolts seemed to be tight, when car was on ramps, wasn't exactly easy getting a socket set in there. The next morning started engine, could smell the product coming out of the exhaust, but there was no thumps, heavy knocks, or noises at start up indicating that perhaps the main bearings are fine; then took it for a drive. After about 30 minutes it started making the knocking noise again, but only at the lights with my foot on the brake and when it is of course in "D" on the powerglide. It doesn't make any noise when it is in "N" or "P" when idling, even if I let it idle for a long time. I'm thinking perhaps the noise is coming from the powerglide, as it sounds like it is coming from below the vehicle as opposed to a pushrod up top, but I can't be exactly sure. It's not really bothering me too much because it disappears once the car is in motion again, and doesn't do it all the time.
