I’m not sure I’d use STP in a steering gear. Especially where I live. I use it once in a Model A transmission and one morning when it got below freezing I nearly bent the shift lever trying to shift gears. It would be like anti-power steering in a steering box.

Kevin
1951 Chevy 3100 work truck
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Photos
1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.