I had a major front crankshaft seal leak, and that caused the balance shaft belt to come off. The belt was ruined, so I got another one. Today I installed the belt, and just for grins, I left off the covers, fan and radiator, and started it to make sure there was no leaks (yes I installed the crank pulley!). I started the engine, and revved it up from under the hood. When the engine got to about 2,500 RPM, I heard a weird sound and noticed that the balance shaft belt vibrated at the same time. I revved it up again, and the same sound and visual vibration. I turned off the engine and put it back on TDC. I noticed that both balance shaft gears were not lined up with the marks. I can only assume that the sound I was hearing was the belt slipping on the gears. Has anyone experienced this before? Does anyone know what would cause this? Just for fun, I changed out the tensioner with a known good one, and timed up the belt and fired it up again. Same thing happened again. HELP!!!!