The original lube was very thick, and is no longer available from GM. I think the thicker stuff makes it less likely to leak from the seal around the sector shaft. But some folks use SAE 90 gear lube, and I guess do ok. I used Penrite steering box lube. Very expensive, and no leaks AFTER I installed a GM seal on the sector shaft. The one in the rebuild kit was garbage. Others use STP, I wonder if they had good results?
