Also known as a Castle nut that adjusts the wheel bearing on the spindle.

https://www.fillingstation.com/catalog/flippingbook/index.html#260/z

Scroll down towards the bottom of that page.

Has them $2.25 each. 3/4" x 20 nut GM # 378137. Appears same part from 1935 to 1972.

Chevys of the 40's has the nuts with the washer that goes on before the nut. They list the same GM#.

Last edited by 32vld; 07/08/2015 2:22 AM.