Before anyone gets the impression that I'm flaming Amsoil, let me tell you that I am not. I still believe in the product, but the only thing that has got my leak to stop is draining all of the gear lube out of the differential and adding straight 80W-90 gear lube. Every pinion seal problem I had occurred with Amsoil 75W-90 or 140 in the differential. My truck may have an imperfection in the driveline that is so small that the synthetic is finding the "weak" spot, so to speak. I don't know, but what I do see is a dry differential bottom and that is nice. Any suggestions for a high quality non-synthetic gear lube. I put Valvoline in the truck this time. I plan on changing the lube every 15-20K, depending upon how many miles I tow. TIA
John
John